<html>

<head>
<meta http-equiv="Content-Language" content="en-us">
<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>

  Filesystem TR2 Proposal
  </title>
<style type="text/css">
/*

   Copyright Beman Dawes, 2007

  Distributed under the Boost Software License, Version 1.0.
  See www.boost.org/LICENSE_1_0.txt
  
*/

body  {
       font-family: sans-serif;
       margin: 1em;
       max-width : 8.5in;
	 }

table   { margin: 0.5em; }

pre     { background-color:#D7EEFF }

ins     { background-color:#A0FFA0 }
del     { background-color:#FFA0A0 }

/*** end ***/
</style>
</head>

<body>

  <table border="0" cellpadding="0" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="579">
    <tr>
      <td width="153" align="left" valign="top">Document number:</td>
      <td width="426">N3365=12-0055</td>
    </tr>
    <tr>
      <td width="153" align="left" valign="top">Date:</td>
      <td width="426">
      <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%Y-%m-%d" startspan -->2012-02-27<!--webbot bot="Timestamp" endspan i-checksum="12118" --></td>
    </tr>
    <tr>
      <td width="153" align="left" valign="top">Project:</td>
      <td width="426">Programming Language C++, Library Working Group</td>
    </tr>
    <tr>
      <td width="153" align="left" valign="top">Reply-to:</td>
      <td width="426">Beman Dawes &lt;bdawes at acm dot org&gt;</td>
    </tr>
  </table>


<h1>Filesystem Library Proposal (Revision 2)</h1>


<p>This paper proposes a filesystem library component suitable for a <i>C++ 
Standard Library Technical Report</i> or for the <i>C++ Standard Library</i>. 
The proposed library is based on Version 3 of the Boost Filesystem 
Library (see <a href="http://www.boost.org/libs/filesystem">
www.boost.org/libs/filesystem</a>). Preliminary wording is provided. A
<a href="#TODO">TODO</a> list identifies remaining work to be done.</p>


<h2>Revision history </h2>


<p>N3365=12-0055, Filesystem Library Proposal (Revision 
2). Changes 
include:</p>


<ul>
  <li>Namespaces changed to <code>std::tbd::filesystem</code> per 
  <a href="#Issues-List">issue 
  1</a> discussion in Kona.</li>
  <li>Removed references to Boost within the proposed wording.</li>
  <li>Minor fixes to the proposed wording.</li>
  <li>Added Issue 7: How should class path inserter and extractor be specified?</li>
  <li>Marked up all issues to reflect Kona LWG discussions.</li>
</ul>


<p><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3335.html">
N3335=12-0025</a>, Filesystem Library for C++11/TR2 (Revision 1). Changes 
include:</p>


  <ul>
    <li>Regenerated the proposed wording from the Boost Filesystem library 
    reference documentation, using an automated process. This process reduces 
    the likelihood of inadvertent discrepancies between descriptions.</li>
    <li>An <a href="#Issues-List">Issues list</a> was added, seeded with issues 
    raised by the LWG review of N3239 at the Bloomington meeting, and private 
    communications from LWG members.</li>
    <li>Namespace changed to <code>files</code> as an experiment. Made this 
    issue number 1 so the LWG can pass judgment.</li>
    <li>New functions were added, suggested by David Svoboda, to generate 
    canonical paths and manage permissions.</li>
    <li>More C++11 functionality was applied. This process is still incomplete, 
    however.</li>
    <li>Added proposed changes to header &lt;fstream&gt;. The previous paper had 
    inadvertently supplied the wrong wording.</li>
    <li>Continued the general cleanup of wording.</li>
</ul>


<p><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3239.html">
N3239 = 11-0009</a>, Filesystem Library Update for TR2 (Preliminary), reflected 
changes made to the Boost library version 3 since the previously accepted 
committee paper:</p>


  <ul>
    <li>A single class <code>path</code> handles all aspects of 
    internationalization, replacing the previous template and its <code>path</code> 
    and <code>wpath</code> instantiations. Character types <code>char</code>,
    <code>wchar_t</code>, <code>char16_t</code>, and <code>char32_t</code> are 
    supported. This is a major simplification of the path abstraction, 
    particularly for functions that take path arguments. This change was based 
    on a suggestion by Peter Dimov.</li>
    <li>Several operational functions have been added, including much better 
    symlink support, the ability to resize a file, and the ability to generate a 
    unique path.</li>
    <li>Support for error reporting via <code>error_code</code> is now uniform 
    throughout the operations functions.</li>
    <li>Several functions have been renamed, based on feedback from users.</li>
  </ul>


<p><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1975.html">
N1975 = 06-0045</a>, Filesystem Library Proposal for TR2 (Revision 3), was 
adopted by the committee in April, 2006, at the Berlin meeting. Shortly 
afterward the Library Working Group set aside work on TR2 to concentrate on 
C++0x.</p>


<h2>Motivation and Scope</h2>


<p>The motivation and scope for a filesystem library were described in <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1975.html">
N1975</a>, and are not repeated here. A minor scope reduction is that an 
addition to the current C++ runtime library is no longer needed.</p>


<p>Boost Filesystem Version 3  introduced a single path type that interoperates well with both <code>
basic_string</code> and user defined string types. Thus the following Design 
alternatives paragraph is no long applicable:</p>


  <blockquote>


<p><strike><i>Single path type which can at runtime accept narrow or wide character 
pathnames.</i> Although certainly interesting, and possibly superior, such a 
design would not interoperate well with the current Standard Library's 
compile-time typed <code>basic_string</code>. A new runtime polymorphic string 
class would be the best place to experiment with this concept, not a path class.</strike></p>


  </blockquote>


  <h2><a name="TODO">TODO</a></h2>
  <ul>
    <li>Apply more C++0X features. Boost.Filesystem needs to implement these to verify their 
    application is correct.</li>
    <li>Boost.Filesystem needs to implement <code>char16_t</code> and <code>char32_t</code> support to verify the 
    specification for these is correct.</li>
    <li>The Boost implementation has more class path non-member relational 
    functions that shown in the docs, and the specific set of relational 
    functions varies between Windows and POSIX. Figure out what's happening and 
    document it.</li>
    <li><code><a href="#Source">Source</a></code> is not specified as actually 
    implemented. Expose <code>path_traits</code>?</li>
    <li><i>Effects</i> for <code>copy</code> and <code>copy_directory</code> 
    need to be reviewed, revised, tested, peer reviewed.</li>
    <li>Dinkumware/Microsoft report slightly different results for Decomposition 
    table. Rerun table. Check discrepancies.</li>
    <li>Apply issue resolutions from Kona.</li>
    <li>Remove registered trademarks from normative text per ISO policy.</li>
    <li>Review Nick Stoughton's email for suggestions, action items.</li>
    <li>Change <code>time_t</code> to <code>chrono system_clock::time_point</code>, 
    per LWG discussion in Kona. </li>
    <li>Add [section.name] and, if possible, section numbering, per LWG 
    discussion in Kona. </li>
  </ul>
  
  

<h2><a name="TOC">Table of Contents</a></h2>

<table border="0" cellpadding="0" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="100%">
  <tr>
    <td width="33%" valign="top"><a href="#Introduction">Introduction</a><br>
    <a href="#Definitions">Definitions</a><br>
    <a href="#Conformance">Conformance</a><br>
    <a href="#Header-filesystem-synopsis">
    Header <code>&lt;filesystem&gt;</code> synopsis</a><br>
    <a href="#Error-reporting">Error reporting</a><br>
    <a href="#class-path">Class <code>path</code></a><br>
&nbsp;&nbsp;&nbsp; <a href="#path-Conversions"><code>path</code> conversions</a><br>
&nbsp;&nbsp;&nbsp; <a href="#path-Conversions-to-native-format"><code>path</code> 
    conversions to native format</a><br>
&nbsp;&nbsp;&nbsp; <a href="#path-Conversions-to-generic-format"><code>path</code> 
    conversions to generic format</a><br>
&nbsp;&nbsp;&nbsp; <a href="#path-Encoding-conversions"><code>path</code> 
    encoding conversions</a><br>
&nbsp;&nbsp;&nbsp; <a href="#path-Requirements"><code>path</code> requirements</a><br>
    &nbsp;&nbsp;&nbsp; <a href="#path-constructors"><code>path</code> constructors</a><br>
&nbsp;&nbsp;&nbsp; <a href="#path-assignments"><code>path</code> assignments</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#path-appends"><code>path</code> appends</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#path-modifiers"><code>path</code> modifiers</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#path-native-format-observers"><code>path</code> native 
    format observers</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#path-generic-format-observers"><code>path</code> generic 
    format observers</a><br>
&nbsp;&nbsp;&nbsp; <a href="#path-decomposition"><code>path</code> decomposition</a><br>
&nbsp;&nbsp;&nbsp; <a href="#path-query"><code>path</code> query</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#path-iterators"><code>path</code> iterators</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#path-non-member-functions"><code>path</code> non-member functions</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#path-inserter-extractor"><code>path</code> inserters and extractors</a><br>
 &nbsp;<a href="#Class-filesystem_error">Class <code>filesystem_error</code></a><br>
&nbsp;&nbsp;&nbsp; <a href="#filesystem_error-members"><code>filesystem_error</code> 
    constructors</a><br>
&nbsp;&nbsp;&nbsp; <code>f</code><a href="#filesystem_error-path1"><code>ilesystem_error</code> path1</a><br>
&nbsp;&nbsp;&nbsp; <a href="#filesystem_error-path2"><code>filesystem_error</code> path2</a><br>
&nbsp;&nbsp;&nbsp; <a href="#filesystem_error-what"><code>filesystem_error</code><code>
    </code>what</a></td>
    <td width="33%" valign="top">
    <a href="#Enum-file_type">Enum <code>file_type</code></a><br>
    <a href="#Enum-perms">Enum <code>perms</code></a><br>
    <a href="#file_status">Class 
    <code>file_status</code></a><br>
&nbsp;&nbsp;&nbsp;
    <a href="#file_status"> 
    <code>file_status</code></a><a href="#file_status-constructors"> constructors</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<code><a href="#file_status-modifiers">file_status-modifiers</a></code><a href="#directory_entry-observers"> observers</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<code><a href="#file_status-observers">file_status-observers</a></code><a href="#directory_entry-modifiers"> modifiers</a><br>
<a href="#Class-directory_entry">Class <code>directory_entry</code></a><br>
&nbsp;&nbsp;&nbsp;
<a href="#directory_entry-constructors"><code>directory_entry</code> constructors</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#directory_entry-observers"><code>directory_entry</code> observers</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#directory_entry-modifiers"><code>directory_entry</code> modifiers</a><br>
<a href="#Class-directory_iterator">Class  <code>directory_iterator</code></a><br>
&nbsp;&nbsp;&nbsp; <a href="#directory_iterator-members"><code>directory_iterator</code> 
    members</a><br>
<a href="#Class-recursive_directory_iterator">Class <code>recursive_directory_iterator</code></a><br>
    <a href="#Operational-functions">
    Operational functions</a><br>
    <code>&nbsp;&nbsp;&nbsp;&nbsp <a href="#absolute">absolute</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; <a href="#canonical">canonical</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; <a href="#copy">copy</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; <a href="#copy_directory">copy_directory</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; <a href="#copy_file">copy_file</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; <a href="#copy_symlink">copy_symlink</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#create_directories">create_directories</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#create_directory">create_directory</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#create_hard_link">create_hard_link</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#create_symlink">create_symlink</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#current_path">current_path</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#exists">exists</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#equivalent">equivalent</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#file_size">file_size</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; <a href="#hard_link_count">hard_link_count</a><br>
    &nbsp;&nbsp;&nbsp;&nbsp; <a href="#initial_path">initial_path</a><br>
&nbsp;&nbsp;&nbsp;&nbsp  i<a href="#is_directory">s_directory</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#is_empty">is_empty</a></code></td>
    <td width="34%" valign="top">
    <code>&nbsp;&nbsp;&nbsp;&nbsp <a href="#is_other">is_other</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#is_regular_file">is_regular_file</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#is_symlink">is_symlink</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#last_write_time">last_write_time</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; <a href="#permissions">permissions</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; <a href="#read_symlink">read_symlink</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#remove">remove</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#remove_all">remove_all</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#rename">rename</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; <a href="#resize_file">resize_file</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#space">space</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#status">status</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#status_known">status_known</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#symlink_status">symlink_status</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#system_complete">system_complete</a><br>
&nbsp;&nbsp;&nbsp;&nbsp <a href="#temp_directory_path">temp_directory_path</a><br>
&nbsp;&nbsp;&nbsp;&nbsp; </code> <code> <a href="#unique_path">unique_path</a></code><br>
    <a href="#File-streams">File streams</a><br>
<a href="#Path-decomposition-table">Path decomposition table</a><br>
    <a href="#long-path-warning">Warning: Long paths on Windows and the 
    extended-length <b>\\?\ </b>prefix</a><br>
<a href="#Acknowledgements">Acknowledgements</a><br>
<a href="#References">References</a><br>
&nbsp;</td>
  </tr>
</table>


<h2>Proposed Wording</h2>

<p><span style="font-style: italic; background-color: rgb(224, 224, 224);">
Gray-shaded italic text is commentary on the proposal. It is not to be added to 
the TR.</span></p>
<p><span style="font-style: italic; background-color: #E0E0E0">Add the following 
to the Technical Report's front matter:</span></p>
<p>The following standard contains provisions which, through reference in this 
text, constitute provisions of this Technical Report. At the time of 
publication, the editions indicated were valid. All standards are subject to 
revision, and parties to agreements based on this Technical Report are 
encouraged to investigate the possibility of applying the most recent editions 
of the standard indicated below. Members of IEC and ISO maintain registers of 
currently valid International Standards.</p>
<ul>
  <li>ISO/IEC 9945:2003, <i>Portable Operating System Interface (POSIX<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1975.html#Footnote-1"><sup>1</sup></a>), 
  part 1 (Base Definitions) and part 2 (System Interfaces)</i>, both as 
  corrected by their respective 2004 Correction 1 documents.<p>[<i>Note:</i> 
  ISO/IEC 9945:2003 is also IEEE&nbsp;Std&nbsp;1003.1-2001, and The Open Group Base 
  Specifications, Issue 6, and is also known as The Single Unix<font face="Times New Roman"><sup><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1975.html#Footnote-2">2</a></sup><i><b>
  </b></i>Specification, Version 3. It is available from each of those 
  organizations, and may be read online or downloaded from
  <a href="http://www.unix.org/single_unix_specification/">
  www.unix.org/single_unix_specification/</a> <i>-- end note</i>]</font></li>
</ul>
<p>ISO/IEC 9945:2003, with the indicated corrections, is hereinafter called <i>
POSIX</i>.</p>
<p><a name="Footnote-1">Footnote 1</a>: <i>POSIX</i> is a registered trademark 
of The IEEE.</p>
<p><a name="Footnote-2">Footnote 2</a>: <i>UNIX</i> is a registered trademark 
of The Open Group.</p>
<p><span style="font-style: italic; background-color: #E0E0E0">Add the following 
to the Technical Report as a new Clause:</span></p>
<h2>Filesystem Library</h2>



<p>This Clause describes components that perform operations on file systems and 
their components, such as paths, regular files, and directories.</p>
<p dir="ltr">Operating systems such as <i>Linux, MAC OS, UNIX</i>, and <i>Windows</i> are 
mentioned in this Clause for purposes of illustration or to give guidance to 
implementers. No slight to other operating systems is implied or intended.</p>
<p><span style="background-color: #E0E0E0">Footnote:</span> Linux is a 
registered trademark of Linus Torvalds.</p>
<p><a name="Footnote-3"><span style="background-color: #E0E0E0">Footnote</span></a><span style="background-color: #E0E0E0">:</span> <i>MAC OS</i> is a registered trademark 
of Apple Inc.</p>
<p><span style="background-color: #E0E0E0">Footnote:</span> <i>UNIX</i> is a 
registered trademark of The Open Group. </p>
<p><a name="Footnote-4"><span style="background-color: #E0E0E0">Footnote</span></a><span style="background-color: #E0E0E0">:</span> <i>Windows</i> is a registered 
trademark of Microsoft Corporation.</p>

<h2><a name="Conformance">Conformance</a></h2>
<p>Behavior is sometimes specified by reference to ISO/IEC 9945:2003, <i>
<a href="http://www.unix.org/single_unix_specification/">POSIX</a></i>. How such behavior is actually implemented is unspecified.</p>
<blockquote>
<p>[<i>Note:</i> This constitutes an &quot;as if&quot; rule for implementation of 
operating system dependent behavior. Presumably implementations will usually call native 
operating system API's. <i>--end note</i>]</p>
</blockquote>
<p>Implementations are encouraged, but not required, to support such behavior 
 
as it is defined by <i>POSIX</i>. Implementations shall document any 
behavior that differs from the <i>POSIX</i> defined behavior. Implementations that do not support exact <i>POSIX</i> behavior are 
encouraged to provide behavior as close to <i>POSIX</i> behavior as is reasonable given the 
limitations of actual operating systems and file systems. If an implementation cannot provide any 
reasonable behavior, the implementation shall report an error in an 
implementation-defined manner.</p>
<blockquote>
<p>[<i>Note:</i> Such errors might be reported by an #error directive, a <code>
static_assert</code>, a <code>filesystem_error</code> exception, a special 
return value, or some other manner. <i>--end note</i>]</p>
</blockquote>
<p>Implementations are not required to provide behavior that is not supported by 
a particular file system.</p>
<blockquote>
<p>[<i>Example:</i> The <a href="http://en.wikipedia.org/wiki/FAT_filesystem">
FAT file system</a> used by some memory cards, camera memory, and floppy discs 
does not support hard links, symlinks, and many other features of more capable 
file systems. Implementations are only required to support the FAT features 
supported by the host operating system. <i>-- end example</i>]</p>
</blockquote>
<p>Specific operating systems such as <i>OpenVMS</i>,
<i>UNIX</i>, and <i>Windows</i> are mentioned only for purposes of illustration or to 
give guidance to users and implementers. No slight to other operating systems is implied 
or intended. When unlikely to cause confusion, the term <i>POSIX</i> is 
sometimes used to refer to &quot;POSIX-compliant operating systems&quot;.</p>
<p>The behavior of functions described in this 
reference 
may differ from their specification in 
the presence of <a href="#Race-condition">file system races</a>. No diagnostic is required.</p>
<p>If the possibility of a file system race would make it unreliable for a program to 
test for a precondition before calling a function described in this Clause, <i>
Requires</i> is not specified for the condition. Instead, the condition is 
specified as a <i>Throws</i> condition.</p>
<blockquote>
<p>[<i>Note:</i> As a design practice, preconditions are not specified when it 
is unreasonable for a program to detect them prior to calling the function. <i>
-- end note</i>]</p>
</blockquote>
<h2><a name="Definitions">Definitions</a></h2>
<p>The following definitions  shall apply throughout this reference documentation:</p>
<p><i><b><a name="File">File</a>:</b> </i>An object that can be written to, or read from, or both. A file 
has certain attributes, including type. File types include regular files 
and directories. Other types of files, such as symbolic links, may be supported by the 
implementation.</p>
<p><b><i><a name="File-system">File system</a>:</i></b> A collection of files and certain of their attributes.</p>
<p><b><i><a name="Filename">Filename</a>:</i></b> The name of a file. Slash and 
0x00 
characters are not permitted. Implementations may define additional 
characters or specific names that are not permitted. Filenames <code>.</code>&nbsp; 
and <code>..</code>&nbsp; have special meaning. Implementations may define 
additional filenames that have special meaning.</p>
<blockquote>
  <p><i>[Note:</i> Most operating systems prohibit the ASCII control characters 
  (0x00-0x1F) in filenames.</p>
  <p>Windows prohibits the characters 0x00-0x1F, <code>&quot;</code>,<code> 
  *</code>,<code>&nbsp;:</code>,<code> &lt;</code>,<code> &gt;</code>,<code>&nbsp;?</code>,<code> 
  \</code>,<code> /</code>, and<code> |</code>&nbsp;<i>--end note]</i></p>
</blockquote>
<p><b><i><a name="Path">Path</a>:</i></b> A sequence of elements that identify 
the location of a file within a filesystem. The elements are the <i>root-name<sub>opt</sub></i>, <i>
root-directory<sub>opt</sub></i>, and an optional sequence of filenames. [<i>Note:</i> 
A <a href="#Pathname">pathname</a> is the concrete representation of a path. <i>--end note</i>]</p>
<p><b><i><a name="Absolute-path">Absolute path</a>:</i></b> A path that 
unambiguously 
identifies the location of a file within a file system without reference to an 
additional starting location. The format is implementation defined. </p>
<blockquote>
  <p><i>[Note:</i> For POSIX-like implementations, including<b> </b>Unix 
  variants, Linux, and Mac OS X, only paths 
  that begin with a slash are absolute paths.</p>
  <p>For Windows-like implementations, including <a href="http://www.cygwin.com/">
  Cygwin</a> and
  <a href="http://www.mingw.org/">MinGW</a>, only paths that begin with a drive 
  specifier followed by a slash, or begin with two slashes, are absolute paths.&nbsp;<i>--end 
  note]</i></p>
</blockquote>
<p><i><b><a name="Relative-path">Relative path</a>:</b></i> A path that only 
unambiguously 
identifies the location of a file within a filesystem when resolved relative to 
a starting location. The format is implementation defined. [<i>Note:</i> 
Paths &quot;.&quot; and &quot;..&quot; are considered to be relative paths. <i>--end note</i>]</p>
<p><i><b><a name="Canonical-path">Canonical path</a>:</b></i> An absolute path that has 
no elements which are symbolic links, and no dot or dot dot elements.</p>
<p><i><b><a name="Pathname">Pathname</a>:</b> </i>A character string that represents a 
path. Pathnames are formatted according to the generic pathname format or an implementation defined 
native pathname format.</p>
<p><b><i><a name="generic-pathname-format">Generic pathname format:</a></i></b></p>
<blockquote>
<p><i>pathname:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; root-name<sub>opt</sub> 
root-directory<sub>opt</sub> relative-path<sub>opt</sub></i></p>
<p><i>root-name:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
implementation-defined</i></p>
<blockquote>
  <blockquote>
<p>[<i>Note:</i> Most POSIX and Windows based operating systems define a name 
beginning with two slashes (or backslashes, for Windows) as a root-name 
identifying network locations. Windows defines a single letter followed by a
<code>&quot;:&quot;</code> as a root-name identifying a disc drive. <i>--end note</i>]</p>
  </blockquote>
</blockquote>
<p><i>root-directory:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
directory-separator</i></p>
<p><i>relative-path:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
filename<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; relative-path 
directory-separator<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; relative-path 
directory-separator filename</i></p>
<p><i>filename:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; name<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </i><code>&quot;.&quot;</code><i><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </i><code>
&quot;..&quot;</code></p>
<p><i>directory-separator:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <code>&quot;/&quot;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &quot;/&quot;</code> directory-separator</i></p>
<p>Multiple successive <i>directory-separator</i> characters are considered to 
be the same as one <i>directory-separator</i> character. The <i>filename</i>
<code>&quot;.&quot;</code> is considered to be a reference to the current directory. The
<i>filename</i> <code>&quot;..&quot;</code> is considered to be a reference to the current 
directory. Specific <i>filenames</i> may have special meaning for a particular 
operating system.</p>
</blockquote>
<p><b><i><a name="native-pathname-format">Native pathname format:</a></i></b>&nbsp; 
An implementation defined format. [<i>Note:</i> For POSIX-like operating 
systems, the native format is the same as the generic format. For Windows, the 
native format is similar to the generic format, but the directory-separator 
characters can be either slashes or backslashes. <i>--end note</i>]</p>
<p><i><b><a name="Link">Link</a>:</b> </i>A directory entry object that associates a 
filename with a file. On some file systems, several directory entries can 
associate names with the same file.</p>
<p><b><i><a name="Hard-link">Hard link</a>:</i></b> A link to an existing file. Some 
file systems support multiple hard links to a file. If the last hard link to a 
file is removed, the file itself is removed.</p>
<blockquote>
<p>[<i>Note:</i> A hard link can be thought of as a shared-ownership smart 
pointer to a file.<i> -- end note</i>]<i> </i></p>
</blockquote>
<p><i><a name="Symbolic-link">S<b>ymbolic link</b></a><b>:</b> </i>A type of file with the 
property that when the file is encountered during pathname resolution, a string 
stored by the file is used to modify the pathname resolution.</p>
<blockquote>
<p>[<i>Note:</i> A symbolic link can be thought of as a raw pointer to a file. 
If the file pointed to does not exist, the symbolic link is said to be a 
&quot;dangling&quot; symbolic link.<i> -- end note</i>]<i> </i></p>
</blockquote>
<p><b><i><a name="Race-condition">File system race</a>:</i></b> The condition that occurs 
when multiple threads, processes, or computers interleave access and 
modification of 
the same object within a file system.</p>
<p><b><i><a name="Dot">Dot</a>, Dot Dot:</i></b> Synonyms for the filenames <code>&quot;.&quot;</code> 
and <code>&quot;..&quot;</code>, respectively. The dot filename names the current 
directory. The dot dot filename names the parent directory.</p>
<h2><a name="Header-filesystem-synopsis">Header <code>&lt;filesystem&gt;</code> synopsis</a></h2>
<pre>namespace std { namespace tbd { namespace filesystem {

    class <a href="#class-path">path</a>;

    void swap(path&amp; lhs, path&amp; rhs);
    bool lexicographical_compare(path::iterator first1, path::iterator last1,
                                 path::iterator first2, path::iterator last2);
    std::size_t <a href="#hash_value">hash_value</a>(const path&amp; p);

    bool operator==(const path&amp; lhs, const path&amp; rhs);
    bool operator!=(const path&amp; lhs, const path&amp; rhs);
    bool operator&lt; (const path&amp; lhs, const path&amp; rhs);
    bool operator&lt;=(const path&amp; lhs, const path&amp; rhs);
    bool operator&gt; (const path&amp; lhs, const path&amp; rhs);
    bool operator&gt;=(const path&amp; lhs, const path&amp; rhs);

    path operator/ (const path&amp; lhs, const path&amp; rhs);

    std::ostream&amp;  operator&lt;&lt;( std::ostream&amp; os, const path&amp; p );
    std::wostream&amp; operator&lt;&lt;( std::wostream&amp; os, const path&amp; p );
    std::istream&amp;  operator&gt;&gt;( std::istream&amp; is, path&amp; p );
    std::wistream&amp; operator&gt;&gt;( std::wistream&amp; is, path&amp; p )

    class <a href="#Class-filesystem_error">filesystem_error</a>;      
    class <a href="#Class-directory_entry">directory_entry</a>;

    class <a href="#Class-directory_iterator">directory_iterator</a>;

    class <a href="#Class-recursive_directory_iterator">recursive_directory_iterator</a>;

    enum <a name="file_type" href="#Enum-file_type">file_type</a>
    {
      status_error, file_not_found, regular_file, directory_file,
      symlink_file, block_file, character_file, fifo_file, socket_file,
      type_unknown
    };

    enum <a href="#Enum-perms">perms</a>
    {
      no_perms,
      owner_read, owner_write, owner_exe, owner_all,
      group_read, group_write, group_exe, group_all,
      others_read, others_write, others_exe, others_all, all_all,
      set_uid_on_exe, set_gid_on_exe, sticky_bit,
      perms_mask, perms_not_known,
      add_perms, remove_perms, symlink_perms
    };

    class <a href="#file_status">file_status</a>;

    struct <a name="space_info">space_info</a>  // returned by <a href="#space" style="text-decoration: none">space</a> function
    {
      uintmax_t capacity;
      uintmax_t free; 
      uintmax_t available; // free space available to a non-privileged process
    };

    enum class <a name="copy_option">copy_option</a>
    {
      none
      fail_if_exists = none,
      overwrite_if_exists
    };

    enum class <a name="symlink_option">symlink_option</a>
    {
      none
      no_recurse = none,
      recurse
    };

    // <a href="#Operational-functions">operational functions</a>

    path         <a href="#absolute">absolute</a>(const path&amp; p, const path&amp; base=current_path());

    path         <a href="#canonical">canonical</a>(const path&amp; p, const path&amp; base = current_path());
    path         <a href="#canonical">canonical</a>(const path&amp; p, system::error_code&amp; ec);
    path         <a href="#canonical">canonical</a>(const path&amp; p, const path&amp; base, system::error_code&amp; ec);

    void         <a href="#copy">copy</a>(const path&amp; from, const path&amp; to);
    void         <a href="#copy">copy</a>(const path&amp; from, const path&amp; to, system::error_code&amp; ec);

    void         <a href="#create_directory">copy_directory</a>(const path&amp; from, const path&amp; to);
    void         <a href="#create_directory">copy_directory</a>(const path&amp; from, const path&amp; to, system::error_code&amp; ec);

    void         <a href="#copy_file">copy_file</a>(const path&amp; from, const path&amp; to);
    void         <a href="#copy_file">copy_file</a>(const path&amp; from, const path&amp; to, system::error_code&amp; ec);
    void         <a href="#copy_file">copy_file</a>(const path&amp; from, const path&amp; to, <a href="#copy_option">copy_option</a> option);
    void         <a href="#copy_file">copy_file</a>(const path&amp; from, const path&amp; to, <a href="#copy_option">copy_option</a> option,
                           system::error_code&amp; ec);

    void         <a href="#copy_symlink">copy_symlink</a>(const path&amp; existing_symlink, const path&amp; new_symlink);
    void         <a href="#copy_symlink">copy_symlink</a>(const path&amp; existing_symlink, const path&amp; new_symlink, system::error_code&amp; ec);

    bool         <a href="#create_directories">create_directories</a>(const path&amp; p);
    bool         <a href="#create_directories">create_directories</a>(const path&amp; p, system::error_code&amp; ec);

    bool         <a href="#create_directory">create_directory</a>(const path&amp; p);
    bool         <a href="#create_directory">create_directory</a>(const path&amp; p, system::error_code&amp; ec);

    void         <a href="#create_directory_symlink">create_directory_symlink</a>(const path&amp; to, const path&amp; new_symlink);
    void         <a href="#create_directory_symlink">create_directory_symlink</a>(const path&amp; to, const path&amp; new_symlink, system::error_code&amp; ec);

    void         <a href="#create_hard_link">create_hard_link</a>(const path&amp; to, const path&amp; new_hard_link);
    void         <a href="#create_hard_link">create_hard_link</a>(const path&amp; to, const path&amp; new_hard_link, system::error_code&amp; ec);

    void         <a href="#create_symlink">create_symlink</a>(const path&amp; to, const path&amp; new_symlink);
    void         <a href="#create_symlink">create_symlink</a>(const path&amp; to, const path&amp; new_symlink, system::error_code&amp; ec);

    path         <a href="#current_path">current_path</a>();
    path         <a href="#current_path">current_path</a>(system::error_code&amp; ec);
    void         <a href="#current_path">current_path</a>(const path&amp; p);
    void         <a href="#current_path">current_path</a>(const path&amp; p, system::error_code&amp; ec);

    bool         <a href="#exists">exists</a>(file_status s) noexcept;
    bool         <a href="#exists">exists</a>(const path&amp; p);
    bool         <a href="#exists">exists</a>(const path&amp; p, system::error_code&amp; ec) noexcept;

    bool         <a href="#equivalent">equivalent</a>(const path&amp; p1, const path&amp; p2);
    bool         <a href="#equivalent">equivalent</a>(const path&amp; p1, const path&amp; p2, system::error_code&amp; ec);

    uintmax_t    <a href="#file_size">file_size</a>(const path&amp; p);
    uintmax_t    <a href="#file_size">file_size</a>(const path&amp; p, system::error_code&amp; ec);

    uintmax_t    <a href="#hard_link_count">hard_link_count</a>(const path&amp; p);
    uintmax_t    <a href="#hard_link_count">hard_link_count</a>(const path&amp; p, system::error_code&amp; ec);

    const path&amp;  <a href="#initial_path">initial_path</a>();
    const path&amp;  <a href="#initial_path">initial_path</a>(<code>system::error_code&amp; ec</code>);

    bool         <a href="#is_directory">is_directory</a>(file_status s) noexcept;
    bool         <a href="#is_directory2">is_directory</a>(const path&amp; p);
    bool         <a href="#is_directory2">is_directory</a>(const path&amp; p, system::error_code&amp; ec) noexcept;

    bool         <a href="#is_empty">is_empty</a>(const path&amp; p);
    bool         <a href="#is_empty">is_empty</a>(const path&amp; p, system::error_code&amp; ec);

    bool         <a href="#is_other">is_other</a>(file_status s) noexcept;
    bool         <a href="#is_other2">is_other</a>(const path&amp; p,);
    bool         <a href="#is_other2">is_other</a>(const path&amp; p, system::error_code&amp; ec) noexcept;

    bool         <a href="#is_regular_file">is_regular_file</a>(file_status s) noexcept; 
    bool         i<a href="#is_regular_file2">s_regular_file</a>(const path&amp; p);
    bool         i<a href="#is_regular_file2">s_regular_file</a>(const path&amp; p, system::error_code&amp; ec) noexcept;

    bool         <a href="#is_symlink">is_symlink</a>(file_status s noexcept);
    bool         <a href="#is_symlink2">is_symlink</a>(const path&amp; p);
    bool         <a href="#is_symlink2">is_symlink</a>(const path&amp; p, system::error_code&amp; ec) noexcept;

    std::time_t  <a href="#last_write_time">last_write_time</a>(const path&amp; p);
    std::time_t  <a href="#last_write_time">last_write_time</a>(const path&amp; p, system::error_code&amp; ec);
    void         <a href="#last_write_time2">last_write_time</a>(const path&amp; p, const std::time_t new_time);
    void         <a href="#last_write_time2">last_write_time</a>(const path&amp; p, const std::time_t new_time, system::error_code&amp; ec);

    path         <a href="#read_symlink">read_symlink</a>(const path&amp; p);
    path         <a href="#read_symlink">read_symlink</a>(const path&amp; p, system::error_code&amp; ec);

    bool         <a href="#remove">remove</a>(const path&amp; p);
    bool         <a href="#remove">remove</a>(const path&amp; p, system::error_code&amp; ec);

    uintmax_t    <a href="#remove_all">remove_all</a>(const path&amp; p);
    uintmax_t    <a href="#remove_all">remove_all</a>(const path&amp; p, system::error_code&amp; ec);

    void         <a href="#rename">rename</a>(const path&amp; from, const path&amp; to);
    void         <a href="#rename">rename</a>(const path&amp; from, const path&amp; to, system::error_code&amp; ec);

    void         <a href="#resize_file">resize_file</a>(const path&amp; p, uintmax_t size);
    void         <a href="#resize_file2">resize_file</a>(const path&amp; p, uintmax_t size, system::error_code&amp; ec);

    <a href="#space_info">space_info</a>   <a href="#space">space</a>(const path&amp; p);
    <a href="#space_info">space_info</a>   <a href="#space">space</a>(const path&amp; p, system::error_code&amp; ec);

    <a href="#file_status">file_status</a>  <a href="#status">status</a>(const path&amp; p);
    <a href="#file_status">file_status</a>  <a href="#status">status</a>(const path&amp; p, system::error_code&amp; ec) noexcept;

    bool         <a href="#status_known">status_known</a>(file_status s) noexcept;

    <a href="#file_status">file_status</a>  <a href="#symlink_status">symlink_status</a>(const path&amp; p);
    <a href="#file_status">file_status</a>  <a href="#symlink_status">symlink_status</a>(const path&amp; p, system::error_code&amp; ec) noexcept;

    path         <a href="#system_complete">system_complete</a>(const path&amp; p);
    path         <a href="#system_complete">system_complete</a>(const path&amp; p, system::error_code&amp; ec);

    path         <a href="#temp_directory_path">temp_directory_path</a>();
    path         <a href="#temp_directory_path">temp_directory_path</a>(system::error_code&amp; ec);

    path         <a href="#unique_path">unique_path</a>(const path&amp; model=&quot;%%%%-%%%%-%%%%-%%%%&quot;);
    path         <a href="#unique_path">unique_path</a>(const path&amp; model, system::error_code&amp; ec);

} } }  // namespaces std::tbd::filesystem</pre>
<h2><a name="Error-reporting">Error reporting</a></h2>
<p>Filesystem library functions often provide two overloads, one that 
throws an exception to report file system errors, and another that sets an
<code>error_code</code>.</p>
<blockquote>
<p>[<i>Note:</i> This supports two common use cases:</p>
<ul>
  <li>Uses where file system 
errors are truly exceptional and indicate a serious failure. Throwing an 
  exception is the most appropriate response. This is the preferred default for 
  most everyday programming.<br>
&nbsp;</li>
  <li>Uses where file system system errors are routine and do not necessarily represent 
  failure. Returning an error code is the most appropriate response. This allows 
  application specific error handling, including simply ignoring the error.</li>
</ul>
  <p><i>--end note</i>]</p>
</blockquote>
<p>Functions <b>not</b> having an argument of type
<code>system::error_code&amp;</code> 
report errors as follows, unless otherwise specified:</p>
  <ul>
  <li>When a call by the 
  implementation to an operating system or other underlying API results in an 
  error that prevents the function from meeting its specifications, an exception 
  of type
<code>filesystem_error</code> is thrown.<br>
&nbsp;</li>
  <li>Failure to allocate storage is reported by throwing an exception as described in the C++ standard, 
  17.6.4.10 [res.on.exception.handling].<br>
&nbsp;</li>
  <li>Destructors throw nothing.</li>
  </ul>
  <p>Functions having an argument of type
<code>system::error_code&amp;</code> report errors as follows, unless otherwise 
  specified:</p>
<ul>
  <li>If a call by the 
  implementation to an operating system or other underlying API results in an 
  error that prevents the function from meeting its specifications, the
<code>system::error_code&amp;</code> argument is set as 
  appropriate appropriate for the specific error. Otherwise, <code>clear()</code> 
  is called on the
<code>system::error_code&amp;</code> argument.<br>
&nbsp;</li>
  <li>Failure to allocate storage is reported by 
  throwing an exception as described in the C++ standard, 
  17.6.4.10 [res.on.exception.handling].</li>
</ul>
<h2><a name="class-path">Class <code>path</code></a></h2>
<p>An object of class <code>path</code> represents a <a href="#Path">path</a>, 
and contains a <a href="#Pathname">pathname</a> Such an object is concerned only with the lexical and syntactic aspects 
of a path. The path does not necessarily exist in external storage, and the 
pathname is not necessarily valid for the current operating 
system or for a particular file system.</p>
<blockquote>
<p>[<i>Example:</i> A <a href="#long-path-warning">long path name on Windows</a> 
is an example of an innocuous appearing path that is not actually valid. <i>-- 
end example</i>]</p>
</blockquote>
<pre>namespace std { namespace tbd { namespace filesystem {

      class path
      {
      public:
        typedef <b><i><a href="#value_type">see below</a></i></b>                                    value_type;  // char for POSIX, wchar_t for Windows
        typedef std::basic_string&lt;value_type&gt;                string_type;
        typedef std::codecvt&lt;wchar_t, char, std::mbstate_t&gt;  codecvt_type;

        // <a href="#path-constructors">constructors</a> and destructor
        path();
        path(const path&amp; p);
        path(path&amp;&amp; p) noexcept;

        template &lt;class <a href="#Source">Source</a>&gt;
          path(Source const&amp; source, const codecvt_type&amp; cvt=codecvt());

        template &lt;class <a href="#InputIterator">InputIterator</a>&gt;
          path(InputIterator begin, InputIterator end, const codecvt_type&amp; cvt=codecvt());

       ~path();

        // <a href="#path-assignments">assignments</a>
        path&amp; operator=(const path&amp; p);
        path&amp; operator=(path&amp;&amp; p) noexcept;

        template &lt;class <a href="#Source">Source</a>&gt;
          path&amp; operator=(Source const&amp; source);

        template &lt;class <a href="#Source">Source</a>&gt;
          path&amp; assign(Source const&amp; source, const codecvt_type&amp; cvt)

        template &lt;class <a href="#InputIterator">InputIterator</a>&gt;
          path&amp; assign(InputIterator begin, InputIterator end, const codecvt_type&amp; cvt=codecvt());

        // <a href="#path-appends">appends</a>
        path&amp; operator/=(const path&amp; p);

        template &lt;class <a href="#Source">Source</a>&gt;
          path&amp; operator/=(Source const&amp; source);

        template &lt;class <a href="#Source">Source</a>&gt;
          path&amp; append(Source const&amp; source, const codecvt_type&amp; cvt);

        template &lt;class <a href="#InputIterator">InputIterator</a>&gt;
          path&amp; append(InputIterator begin, InputIterator end, const codecvt_type&amp; cvt=codecvt());

        // <a href="#path-modifiers">modifiers</a>
        void  <a href="#path-clear">clear</a>();
        path&amp; <a href="#absolute">make_absolute</a>(const path&amp; base);
        path&amp; <a href="#path-make_preferred">make_preferred</a>();  // POSIX: no effect. Windows: convert slashes to backslashes
        path&amp; <a href="#path-remove_filename">remove_filename</a>();
        path&amp; <a href="#path-replace_extension">replace_extension</a>(const path&amp; new_extension = path());
        void  <a href="#path-swap">swap</a>(path&amp; rhs);

        // <a href="#path-native-format-observers">native format observers</a>
        const string_type&amp;  <a href="#native">native</a>() const noexcept;  // native format, encoding
        const value_type*   <a href="#c_str">c_str</a>() const noexcept;   // native().c_str()

        template &lt;class String&gt;
        String <a href="#string-template">string</a>(const codecvt_type&amp; cvt=codecvt()) const;                // native format

        const string        <a href="#string">string</a>(const codecvt_type&amp; cvt=codecvt()) const;   // native format
        const wstring       <a href="#wstring">wstring</a>(const codecvt_type&amp; cvt=codecvt()) const;  // ditto
        const u16string     <a href="#u16string">u16string</a>() const;                                 // ditto
        const u32string     <a href="#u32wstring">u32string</a>() const;                                 // ditto

        // <a href="#path-generic-format-observers">generic format observers</a>
        template &lt;class String&gt;
        String <a href="#generic_string-template">generic_string</a>() const;

        const string        <a href="#generic_string">generic_string</a>(const codecvt_type&amp; cvt=codecvt()) const;   // generic format
        const wstring       <a href="#generic_wstring">generic_wstring</a>(const codecvt_type&amp; cvt=codecvt()) const;  // ditto
        const u16string     <a href="#generic_u16string">generic_u16string</a>() const;                                 // ditto
        const u32string     <a href="#generic_u32wstring">generic_u32string</a>() const;                                 // ditto

        // <a href="#path-decomposition">decomposition</a>
        path  <a href="#path-root_name">root_name</a>() const;
        path  <a href="#path-root_directory">root_directory</a>() const;
        path  <a href="#path-root_path">root_path</a>() const;
        path  <a href="#path-relative_path">relative_path</a>() const;
        path  <a href="#path-parent_path">parent_path</a>() const;
        path  <a href="#path-filename">filename</a>() const;
        path  <a href="#path-stem">stem</a>() const;
        path  <a href="#path-extension">extension</a>() const;

        // <a href="#path-query">query</a>
        bool <a href="#path-query">empty</a>() const;
        bool <a href="#path-has_root_name">has_root_name</a>() const;
        bool <a href="#path-has_root_directory">has_root_directory</a>() const;
        bool <a href="#path-has_root_path">has_root_path</a>() const;
        bool <a href="#path-has_relative_path">has_relative_path</a>() const;
        bool <a href="#path-has_parent_path">has_parent_path</a>() const;
        bool <a href="#path-has_filename">has_filename</a>() const;
        bool <a href="#path-has_stem">has_stem</a>() const;
        bool <a href="#path-has_extension">has_extension</a>() const;
        bool <a href="#path-is_absolute">is_absolute</a>() const;
        bool <a href="#path-is_relative">is_relative</a>() const;

        // <a href="#path-iterators">iterators</a>
        class iterator;
        typedef iterator const_iterator;

        iterator begin() const;
        iterator end() const;
        
        // <a href="#path_encoding">encoding conversion</a>
        static std::locale <a href="#path-imbue">imbue</a>( const std::locale&amp; loc );
        static const codecvt_type &amp; <a href="#path-codecvt">codecvt</a>();

      private:
        string_type pathname;  // <b><i>exposition only</i></b>
      };

} } }  // namespaces std::tbd::filesystem</pre>
<p><code><a name="value_type">value_type</a></code> is an implementation-defined 
<code>typedef</code> for the 
character type used by the operating system to represent pathnames.</p>
<p>Member functions described as returning <code>const string</code>, <code>
const wstring</code>, <code>const u16string</code>, or <code>const u32string</code> are permitted to return <code>const string&amp;</code>, <code>const 
wstring&amp;</code>, <code>const u16string&amp;</code>, or <code>const u32string&amp;</code>, 
respectively.</p>
<blockquote>
<p>[<i>Note:</i> This allows implementations to avoid unnecessary copies when no 
conversion is required. 
Return-by-value is specified as
<code>const</code> to ensure programs won't break if moved to a return-by-reference 
implementation. <i>-- 
end note</i>]</p>
</blockquote>
<h3><a name="path-Conversions"><code>path</code> Conversions</a></h3>
<h4><a name="path-Conversions-to-native-format"><code>path</code> Conversions to 
native format</a></h4>
<p>Member function arguments that take character sequences representing paths 
may use the <a href="#generic-pathname-format">generic pathname format</a> or 
the <a href="#native-pathname-format">native pathname format</a>. If such an 
argument uses the generic format, an implementation defined conversion to native format is performed 
during the processing of the argument. </p>
<blockquote>
<p>[<i>Note:</i> No conversion occurs on POSIX and Windows since they have 
native formats that conform to the generic format. <i>--end note</i>]</p>
<p>[<i>Rationale:</i> There is no unambiguous way for an implementation to 
always be able distinguish between native format and generic format arguments. 
This is by design as it simplifies use. Should an implementation encounter an 
operating system where disambiguation is required, an implementation defined 
native format prefix can be introduced to identify the native format. <i>-- end 
rationale</i>]</p>
</blockquote>

<div align="center">
  <center>

<table border="1" cellpadding="3" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" bgcolor="#E0E0E0" width="90%">
  <tr>
    <td>
    <i>Class <code>path</code> does not currently map invalid characters in 
    filenames to valid characters. In the future we might add something like 
    this:</i><blockquote>
<p><i>When converting filenames to the native operating system format, 
implementations are encouraged, but not required, to convert otherwise invalid 
characters or character sequences to valid characters or character sequences. 
Such conversions are implementation-defined.</i></p>
<blockquote>
<p><i>[Note: Filename conversion allows much wider portability of both 
programs and filenames that would otherwise be possible.</i></p>
<p><i>Implementations are encouraged to base conversion on existing standards or 
practice. Examples include the Uniform Resource Locator escape syntax of a percent sign (<code>'%'</code>) 
followed by two hex digits representing the character value. On OpenVMS, which does not allow percent signs in filenames, a dollar sign (<code>'&#36;'</code>) 
followed by two hex digits is the existing practice, as is converting lowercase 
letters to uppercase. -- end note.]</i></p>
</blockquote>
    </blockquote>
    </td>
  </tr>
</table>

  </center>
</div>

<p>If the native format requires 
paths for regular files to be formatted differently from paths for directories, the 
path shall be treated as a directory path if last element is a separator, 
otherwise it shall be treated as a regular file path.</p>

<blockquote>

<p>[<i>Note</i>: The above paragraph does not apply to POSIX and Windows since 
they use the same format 
for both regular file and directory pathnames. <i>--end note</i>]</p>

<p>[<i>Example:</i> 
On <a href="http://en.wikipedia.org/wiki/OpenVMS">OpenVMS</a>, a path 
constructed from <code>&quot;/cats/jane&quot;</code> would considered a regular file 
path, and have a native format of <code>&quot;[CATS]JANE&quot;</code>, while a 
path constructed from <code>&quot;/cats/jane/&quot;</code> would be considered a 
directory path, and have a native format of <code>&quot;[CATS.JANE]&quot;</code>.
<i>--end example</i>]</p>

</blockquote>
<h4><a name="path-Conversions-to-generic-format"><code>path</code> Conversions 
to generic format</a></h4>
<p><a href="#path-generic-format-observers">Generic format observer</a> 
functions return strings formatted according to the
<a href="#generic-pathname-format">generic pathname format</a>. The conversion 
from generic to native formats is implementation defined.</p>
<blockquote>
<p>[<i>Note:</i> For POSIX, no conversion is performed. For Windows,  backslashes are converted to 
forward slashes. <i>-- end note</i>]</p>
</blockquote>
<h4><a name="path-Encoding-conversions"><code>path</code> Encoding conversions</a></h4>
<p>If the value type of member function arguments that are character sequences 
representing paths is not <code>value_type</code>, 
and no <code>cvt</code> argument is supplied, conversion to <code>value_type</code> 
occurs using an imbued locale. This imbued locale is initialized with a <code>
codecvt</code> facet appropriate for the operating system.</p>
<blockquote>
<p>For Apple OS X implementations, <code>path::value_type</code> 
is <code>char</code>. The default imbued locale provides a UTF-8 <code>codecvt</code> 
facet. [<i>Rationale:</i> &quot;All BSD system functions expect their string 
parameters to be in UTF-8 encoding and nothing else.&quot; See
<a href="http://developer.apple.com/mac/library/documentation/MacOSX/Conceptual/BPInternational/Articles/FileEncodings.html">
Apple docs</a>. <i>-- end rationale</i>]</p>
<p>For Windows-like implementations, including
<a href="http://www.mingw.org/">MinGW</a>, <code>path::value_type</code> is <code>
wchar_t</code>. The default imbued locale provides a <code>codecvt</code> facet 
that invokes Windows <code>MultiByteToWideChar</code> or <code>
WideCharToMultiByte</code> API with a codepage of <code>CP_THREAD_ACP</code> 
if Windows <code>AreFileApisANSI()</code>is true, otherwise codepage <code>
CP_OEMCP</code>. [<i>Rationale:</i> this is the current behavior of C and C++ 
programs that perform file operations using narrow character string to identify 
paths. Changing this in the Filesystem library would be too surprising, 
particularly where user input is involved. <i>-- end rationale</i>]</p>
<p>For all other implementations, including<b> </b>Linux, <code>path::value_type</code> 
is <code>char</code>. The default imbued locale is <code>std::locale(&quot;&quot;)</code>. 
[<i>Rationale:</i> ISO C specifies this as &quot;the locale-specific native 
environment&quot;, while POSIX says it &quot;Specifies an implementation-defined native 
environment.&quot; <i>-- end rationale</i>]</p>
</blockquote>
<h3><a name="path-Requirements"><code>path</code> Requirements</a></h3>
<p>Template parameters named <code><a name="InputIterator">InputIterator</a></code> 
are required meet the 
requirements for a C++ standard library <code>RandomIterator</code> 
compliant iterator. The iterator's value type is required to be <code>char</code>, <code>
  wchar_t</code>, <code>char16_t</code>, or <code>char32_t</code>.</p>
<p>Template parameters named <code><a name="Source">Source</a></code> are required to be one of:</p>
<ul>
  <li>A container with a value type of <code>char</code>, <code>
  wchar_t</code>, <code>char16_t</code>, or <code>char32_t</code>.</li>
  <li>An iterator for a null terminated byte-string. The value type is required 
  to be <code>char</code>, <code>wchar_t</code>, <code>char16_t</code>, or <code>
  char32_t</code>.</li>
  <li>A C-array. The value type is required to be <code>char</code>, <code>
  wchar_t</code>, <code>char16_t</code>, or <code>char32_t</code>.</li>
  <li>A <code>std::filesystem::directory_entry</code>.</li>
</ul>

<h3> <a name="path-constructors"> <code>
<font size="4">path</font></code> constructors</a></h3>
<pre><span style="background-color: #D7EEFF">path();</span></pre>
<blockquote>
  <p><i>Postcondition:</i> <code>empty()</code>.</p>
  </blockquote>
<pre>template &lt;class <a href="#Source">Source</a>&gt;
  path(Source const&amp; source, const codecvt_type&amp; cvt=codecvt());</pre>
<pre>template &lt;class <a href="#InputIterator">InputIterator</a>&gt;
  path(InputIterator begin, InputIterator end, const codecvt_type&amp; cvt=codecvt());</pre>
<blockquote>
  <p><i>Effects:</i> Stores the contents [<code>begin</code>,<code>end</code>) 
  or <code>source</code> in <code>pathname</code>. If the contents are in the 
  generic format and the generic format is unacceptable to the operating 
  system's API, they are converted to the native format. [<i>Note:</i> For 
  POSIX and Windows  implementations, the generic format is already 
  acceptable as a native format, so no generic to native conversion is 
  performed. <i>--end note</i>]</p>
  <p>
  <i>Remarks:</i> If the value type of&nbsp; [<code>begin</code>,<code>end</code>) 
  or <code>source</code> is not <code>value_type</code>, conversion is performed 
  by <code>cvt</code>.</p>
</blockquote>
<h3> <a name="path-assignments"> <code>
<font size="4">path</font></code> assignments</a></h3>
<pre>template &lt;class <a href="#Source">Source</a>&gt;
  path&amp; operator=(Source const&amp; source);</pre>
<pre>template &lt;class <a href="#Source">Source</a>&gt;
  path&amp; assign(Source const&amp; source, const codecvt_type&amp; cvt);</pre>
<pre>template &lt;class <a href="#InputIterator">InputIterator</a>&gt;
  path&amp; assign(InputIterator begin, InputIterator end, const codecvt_type&amp; cvt=codecvt());</pre>
<blockquote>
  <p><i>Effects:</i> Stores the contents [<code>begin</code>,<code>end</code>) 
  or <code>source</code> in <code>pathname</code>. If the contents are in the 
  generic format, they are converted to the native format. [<i>Note:</i> For 
  POSIX and Windows based implementations, the generic format is already 
  acceptable as a native format, so no generic to native conversion is 
  performed. <i>--end note</i>]</p>
  <p>
  <i>Returns: </i><code>*this</code></p>
  <p>
  <i>Remarks:</i> If the value type of&nbsp; [<code>begin</code>,<code>end</code>) 
  or <code>source</code> is not <code>value_type</code>, conversion is performed 
  by <code>cvt</code>.</p>
  </blockquote>
<h3> <a name="path-appends"><code><font size="4"> path</font></code> appends</a></h3>
  <p>The append operations use <code>operator/=</code> to denote their semantic 
  effect of appending the platform's preferred directory separator when needed. The 
  preferred 
  directory separator is implementation-defined.</p>
<blockquote>
    <p align="left">[<i>Note: </i>For POSIX-like implementations, including<b> </b>
    Unix variants, Linux, and Mac OS X, the preferred directory separator is a 
    single forward slash.</p>
    <p align="left">For Windows-like implementations, including 
  <a href="http://www.cygwin.com/">Cygwin</a> and
    <a href="http://www.mingw.org/">MinGW</a>, the preferred directory 
    separator is a single backslash.<i>--end note</i>]</p>
      </blockquote>
<pre>path&amp; operator/=(const path&amp; p);</pre>
<blockquote>
  <p><i>Effects:</i></p>
  <blockquote>
    Appends the preferred directory separator to the contained pathname, unless:<ul>
    <li>an added separator 
    would be redundant, or</li>
    <li>would change an relative path to an absolute path, or</li>
    <li><code>p.empty()</code>, or</li>
    <li><code>*p.native().cbegin()</code> is a directory separator.</li>
  </ul>
    <p>Appends <code>p.native()</code> to <code>pathname</code>.</p>
  </blockquote>
  <p><i>Returns: </i><code>*this</code></p>
</blockquote>
<pre>template &lt;class <a href="#Source">Source</a>&gt;
  path&amp; operator/=(Source const &amp; source);</pre>
<pre>template &lt;class <a href="#Source">Source</a>&gt;
  path&amp; append(Source const &amp; source, const codecvt_type&amp; cvt);</pre>
<pre>template &lt;class <a href="#InputIterator">InputIterator</a>&gt;
  path&amp; append(InputIterator begin, InputIterator end, const codecvt_type&amp; cvt=codecvt());</pre>
<blockquote>
  <p><i>Effects:</i></p>
  <blockquote>
    <p>Appends a native directory separator to the contained pathname, unless:</p>
    <ul>
    <li>an added separator 
    would be redundant, or</li>
    <li>would change an relative path to an absoute path, or</li>
    <li><code>p.empty()</code>, or</li>
    <li><code>*p.native().cbegin()</code> is a separator.</li>
  </ul>
    <p>Appends the contents [<code>begin</code>,<code>end</code>) 
  or <code>source</code> to <code>pathname</code>. If the contents are in the 
    generic format, they are converted to the native format. [<i>Note:</i> For 
    POSIX and Windows based implementations, the generic format is already 
    acceptable as a native format, so no generic to native conversion is 
    performed. <i>--end note</i>]</p>
  </blockquote>
  <p><i>Remarks:</i> If the value type of&nbsp; [<code>begin</code>,<code>end</code>) 
  or <code>source</code> is not <code>value_type</code>, conversion is performed 
  by <code>cvt</code>.</p>
  <p><i>Returns: </i><code>*this</code></p>
  </blockquote>
  
<h3> <a name="path-modifiers"> <code>
<font size="4">path</font></code> modifiers</a></h3>
<pre>void <a name="path-clear">clear</a>();</pre>
<blockquote>
<p><i>Postcondition:</i> <code>this-&gt;empty()</code> is true.</p>
</blockquote>
<pre>path&amp; <a name="path-make_preferred">make_preferred</a>();</pre>
<blockquote>
  <p><i>Effects:</i> The contained pathname is converted to the preferred native 
  format. [<i>Note:</i> On Windows, the effect is to replace slashes with 
  backslashes. On POSIX, there is no effect. <i>-- end note</i>]</p>
  <p><i>Returns:</i> <code>*this</code></p>
</blockquote>

<pre>path&amp; <a name="path-remove_filename">remove_filename</a>();</pre>
<blockquote>
  <p><i>Returns: </i>As if, <code>*this = parent_path();</code></p>
  <p>[<i>Note:</i> This function is needed to efficiently implement <code>
  directory_iterator</code>. It is exposed to allow additional uses. The actual 
  implementation may be much more efficient than <code>*this = parent_path()</code>&nbsp; <i>-- end 
  note</i>]</p>
</blockquote>
<pre>path&amp; <a name="path-replace_extension">replace_extension</a>(const path&amp; new_extension = path());</pre>
<blockquote>
  <p><i>Postcondition: </i> <code>extension() == <i>replacement</i></code>, 
  where <code><i>replacement</i></code> is <code>new_extension</code> if <code>
  new_extension.empty() || new_extension[0] ==</code> the dot character, 
  otherwise <code><i>replacement</i></code> is the dot character followed by
  <code>new_extension</code>.</p>
  <p><i>Returns:</i> <code>*this</code></p>
</blockquote>
<pre><code>void <a name="path-swap">swap</a>(path&amp; rhs) noexcept;</code></pre>
<blockquote>
  <p><i>Effects:</i> 
  Swaps the contents of the two paths.</p>
  <p><i>Complexity: </i>
  constant time.</p>
</blockquote>

<h3> <a name="path-native-format-observers"><code><font size="4">path</font></code> 
native format observers</a></h3>
<p>The string returned by all native format observers is in the
<a href="#native-pathname-format">native pathname format</a>.</p>
<pre>const string_type&amp;  <a name="native">native</a>() const noexcept;</pre>
<blockquote>
<p><i>Returns:</i> <code>pathname</code>.</p>
</blockquote>
<pre>const value_type* <a name="c_str">c_str</a>() const noexcept;</pre>
<blockquote>
<p><i>Returns:</i> <code>pathname.c_str()</code>.</p>
</blockquote>
<pre>template &lt;class String&gt;
String <a name="string-template">string</a>(const codecvt_type&amp; cvt=codecvt()) const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>pathname</code>.</p>
<p><i>Remarks:</i> If <code>string_type</code> is a different type than <code>
String</code>, conversion is performed by <code>cvt</code>.</p>
</blockquote>
<pre>const string <a name="string">string</a>(const codecvt_type&amp; cvt=codecvt()) const;
const wstring <a name="wstring">wstring</a>(const codecvt_type&amp; cvt=codecvt()) const;
const u16string <a name="u16string">u16string</a>() const;
const u32wstring <a name="u32wstring">u32wstring</a>() const; </pre>
<blockquote>
<p><i>Returns:</i> <code>pathname</code>.</p>
<p><i>Remarks:</i> If <code>string_type</code> is a different type than 
function's return type, conversion is performed by <code>cvt</code>.</p>
<p>If <code>string_type</code> is the same type as the 
function's return type, the function is permitted to return by <code>const&amp;</code> 
rather than <code>const</code> value. [<i>Note:</i> For POSIX, this occurs for
<code>string()</code>, for Windows, <code>wstring()</code>. <i>--end note</i>]</p>
</blockquote>

<h3> <a name="path-generic-format-observers"><code><font size="4">path</font></code>
generic format observers</a></h3>
<p>The string returned by all generic format observers is in the
<a href="#generic-pathname-format">generic pathname format</a>.</p>
<p>[<i>Note:</i> For POSIX, no conversion occurs, since the native format and 
generic format are the same. For Windows, backslashes are converted to slashes
<i>--end note</i>]</p>
<pre>template &lt;class String&gt;
String <a name="generic_string-template">generic_string</a>(const codecvt_type&amp; cvt=codecvt()) const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>pathname</code>.</p>
<p><i>Remarks:</i> If <code>string_type</code> is a different type than <code>
String</code>, conversion is performed by
<code>cvt</code>.</p>
</blockquote>
<pre>const string <a name="generic_string">generic_string</a>(const codecvt_type&amp; cvt=codecvt()) const;
const wstring <a name="generic_wstring">generic_wstring</a>(const codecvt_type&amp; cvt=codecvt()) const;
const u16string <a name="generic_u16string">generic_u16string</a>() const;
const u32wstring <a name="generic_u32wstring">generic_u32wstring</a>() const; </pre>
<blockquote>
<p><i>Returns:</i> <code>pathname</code>.</p>
<p><i>Remarks:</i>&nbsp; If <code>string_type</code> is a different type than 
function's return type, conversion is performed by <code>cvt</code>.</p>
<p>If <code>string_type</code> is of the same type as the 
function's return type, and the generic format is the same as the native format, 
the function is permitted to return by <code>const&amp;</code> rather than <code>
const</code> value. [<i>Note:</i> For POSIX, this occurs for <code>string()</code>. 
It never occurs for Windows, because backslashes must be converted to slashes.
<i>--end note</i>]</p>
</blockquote>

<h3> <a name="path-decomposition"> <code><font size="4">path</font></code> 
decomposition</a></h3>
<p><span style="background-color: #E0E0E0"><i>See the
<a href="#Path-decomposition-table">Path decomposition table</a> for examples 
for values returned by decomposition functions. The
<a href="tutorial.html#Using-path-decomposition">Tutorial</a> may also be 
helpful.</i></span></p>
<pre>path <a name="path-root_name">root_name</a>() const;</pre>
<blockquote>
<p><i>Returns:</i> <i>root-name,</i> if <code>pathname</code> includes <i>
root-name</i>, otherwise <code>path()</code>. </p>
</blockquote>
<pre>path <a name="path-root_directory">root_directory</a>() const;</pre>
<blockquote>
<p><i>Returns:</i> <i>root-directory</i>, if <code>pathname</code> includes <i>
root-directory</i>, otherwise <code>path()</code>.</p>
<p>If <i>root-directory</i> is composed of <i>slash name</i>, <i>slash</i> is 
excluded from the returned string.</p>
</blockquote>
<pre>path <a name="path-root_path">root_path</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>root_name() / root_directory()</code></p>
</blockquote>
<pre>path <a name="path-relative_path">relative_path</a>() const;</pre>
<blockquote>
<p><i>Returns:</i> A <code>path</code> composed from <code>pathname</code>, if <code>
!empty()</code>, beginning 
with the first <i>filename</i> after <i>root-path</i>. Otherwise, <code>path()</code>.</p>
</blockquote>
<pre>path <a name="path-parent_path">parent_path</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>(empty() || begin() == --end()) ? path() : <i>pp</i></code>, where
  <code><i>pp</i></code> is constructed as if by 
  starting with an empty <code>path</code> and successively applying <code>
  operator/=</code> for each element in the range <code>begin()</code>, <code>
  --end()</code>.</p>
</blockquote>
<pre>path <a name="path-filename">filename</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>empty() ? path() : *--end()</code></p>
  <p>[<i>Example:</i></p>
  <blockquote>
    <pre><code>std::cout &lt;&lt; path(&quot;/foo/bar.txt&quot;).filename();</code> // outputs &quot;<code>bar.txt</code>&quot;</pre>
  </blockquote>
  <p> <i>--end example</i>]</p>
</blockquote>
<pre>path <a name="path-stem">stem</a>(const path&amp; p) const;</pre>
<blockquote>
  <p><i>Returns:</i> if <code>p.filename()</code>contains a dot but does not 
  consist solely of one or to two dots, returns 
  the substring of <code>p.filename()</code> starting at its beginning and 
  ending at the last dot (the dot is not included). Otherwise, 
  returns <code>
  p.filename()</code>.</p>
  <p>[<i>Example:</i></p>
  <blockquote>
    <pre><code>std::cout &lt;&lt; path(&quot;/foo/bar.txt&quot;).stem();</code> // outputs &quot;<code>bar</code>&quot;
path p = &quot;foo.bar.baz.tar&quot;;
for (; !p.extension().empty(); p = p.stem())
  std::cout &lt;&lt; p.extension() &lt;&lt; '\n';
  // outputs: .tar
  //          .baz
  //          .bar</pre>
  </blockquote>
  <p> <i>--end example</i>]</p>
</blockquote>
<pre>path <a name="path-extension">extension</a>(const path&amp; p) const;</pre>
<blockquote>
  <p><i>Returns:</i> if <code>p.filename()</code> contains a dot but does not 
  consist solely of one or to two dots, returns 
  the substring of <code>p.filename()</code> starting at the rightmost dot 
  and ending at the path's end. Otherwise, returns an empty <code>path</code> 
  object. </p>
  <p><i>Remarks:</i> Implementations are permitted but not required to define additional 
  behavior for file systems which append additional elements to extensions, such 
  as alternate data streams or partitioned dataset names.</p>
  <p>[<i>Example:</i></p>
  <blockquote>
    <pre><code>std::cout &lt;&lt; path(&quot;/foo/bar.txt&quot;).extension(); //</code> outputs &quot;<code>.txt</code>&quot;</pre>
  </blockquote>
  <p> <i>--end example</i>]</p>
  <p>[<i>Note:<b> </b></i>The dot is included in the return value so that 
  it is possible to distinguish between no extension and an empty extension. See
  <a href="http://permalink.gmane.org/gmane.comp.lib.boost.devel/199744">
  http://permalink.gmane.org/gmane.comp.lib.boost.devel/199744</a> for more 
  extensive rationale.&nbsp; <i>-- end note</i>]</p>
</blockquote>
<h3> <a name="path-query"> <code><font size="4">path</font></code> query</a></h3>
<pre>bool <a name="path-empty">empty</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>m_pathname.empty()</code>.</p>
</blockquote>
<pre>bool <a name="path-has_root_path">has_root_path</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>!<a href="#path-root_path">root_path</a>().empty()</code></p>
</blockquote>
<pre>bool <a name="path-has_root_name">has_root_name</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>!<a href="#path-root_name">root_name</a>().empty()</code></p>
</blockquote>
<pre>bool <a name="path-has_root_directory">has_root_directory</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>!<a href="#path-root_directory">root_directory</a>().empty()</code></p>
</blockquote>
<pre>bool <a name="path-has_relative_path">has_relative_path</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>!<a href="#path-has_relative_path">relative_path</a>().empty()</code></p>
</blockquote>
<pre>bool <a name="path-has_parent_path">has_parent_path</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>!<a href="#path-parent_path">parent_path</a>().empty()</code></p>
</blockquote>
<pre>bool <a name="path-has_filename">has_filename</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>!<a href="#path-filename">filename</a>().empty()</code></p>
</blockquote>
<pre>bool <a name="path-has_stem">has_stem</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>!<a href="#path-stem">stem</a>().empty()</code></p>
</blockquote>
<pre>bool <a name="path-has_extension">has_extension</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>!<a href="#path-has_extension">extension</a>().empty()</code></p>
</blockquote>
<pre>bool <a name="path-is_absolute">is_absolute</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>true</code> 
  if the elements of <code>root_path()</code> uniquely identify a directory, else <code>false</code>.</p>
  <p>[<i>Note:</i> On POSIX,<code> 
  path(&quot;/foo&quot;).is_absolute()</code> returns <code>true</code>. On Windows, <code>
  path(&quot;/foo&quot;).is_absolute()</code> returns <code>false</code>. <i>--end note</i>]</p>
</blockquote>
<pre>bool <a name="path-is_relative">is_relative</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>!is_absolute()</code>.</p>
</blockquote>
<h3> <a name="path-iterators"> <code>
<font size="4">path</font></code> iterators</a></h3>
<p> A <code>path::iterator</code> is a constant iterator satisfying all 
the requirements of a bidirectional iterator (C++ Std, 24.1.4 Bidirectional 
iterators [lib.bidirectional.iterators]). Its <code>value_type</code> is <code>
path</code>.</p>
  <p>Calling any non-const member function of a <code>path</code> object 
  invalidates all iterators referring to elements of that object.</p>
<p> The forward traversal order is as follows:</p>
<ul>
  <li>The <i>root-name</i> element, if present.</li>
  <li>The <i>root-directory</i> element, if present, in the generic format. <i>
  [note:</i> the generic format is required to ensure lexicographical 
  comparison works correctly. <i>-- end note</i>]</li>
  <li>Each successive <i>filename</i> element, if present.</li>
  <li><i>Dot</i>, if one or more trailing non-root <i>slash</i> 
  characters are present.</li>
</ul>
  <p>The backward traversal order is the reverse of forward traversal.</p>
  <pre>iterator begin() const;</pre>
<blockquote>
  <p><i>Returns:</i> An iterator for the first present element in the traversal 
  list above. If no elements are present, the end iterator.</p>
</blockquote>
<pre>iterator end() const;</pre>
<blockquote>
  <p><i>Returns:</i> The end iterator.</p>
</blockquote>
 <h3><a name="path_encoding"><code><font size="4"> path</font></code> encoding</a> conversion</h3>
 <pre>static std::locale <a name="path-imbue">imbue</a>(const std::locale&amp; loc);</pre>
<blockquote>
  <p><i>Effects:</i> Stores <code>loc</code> as the default locale for all 
  objects of type <code>path</code>.</p>
  <p><i>Returns:</i> The previous default locale for all objects of type <code>
  path</code>.</p>
</blockquote>
<pre>static const codecvt_type&amp; <a name="path-codecvt">codecvt</a>();</pre>
<blockquote>
  <p><i>Returns:</i> The <code>codecvt</code> facet for the default locale for 
  all objects of type <code>path</code>.</p>
</blockquote>

<h3> <a name="path-non-member-functions"> <code><font size="4">path</font></code>
non-member functions</a></h3>
<pre>void swap( path&amp; lhs, path&amp; rhs )</pre>
<blockquote>
  <p><i>Effects: </i><code>
  lhs.swap(rhs)</code>.</p>
</blockquote>
  <pre>bool lexicographical_compare(path::iterator first1, path::iterator last1,
                             path::iterator first2, path::iterator last2)</pre>
<blockquote>
  <p><i>Returns:</i> <code>true</code> if the sequence of <code>native()</code> 
  strings for the elements defined by the range <code>[first1,last1)</code> is 
  lexicographically less than the sequence of <code>native()</code> strings for 
  the elements defined by the range <code>[first2,last2)</code>. Returns <code>
  false</code> otherwise.</p>
  <p><i>Remarks:</i> If two sequences have the same number of elements and their 
  corresponding elements are equivalent, then neither sequence is 
  lexicographically less than the other. If one sequence is a prefix of the 
  other, then the shorter sequence is lexicographically less than the longer 
  sequence. Otherwise, the lexicographical comparison of the sequences yields 
  the same result as the comparison of the first corresponding pair of elements 
  that are not equivalent.</p>
  <pre>  for ( ; first1 != last1 &amp;&amp; first2 != last2 ; ++first1, ++first2) {
    if (first1-&gt;native() &lt; first2-&gt;native()) return true;
    if (first2-&gt;native() &lt; first1-&gt;native()) return false;
  }
  return first1 == last1 &amp;&amp; first2 != last2;</pre>
  <p>[<i>Note:</i> A <code>path</code> aware<code> lexicographical_compare</code> 
  is provided to avoid infinite recursion in <code>std::lexicographical_compare</code> 
  due to the <code>path</code> iterator's value type itself being <code>path</code>.
  <i>--end note</i>]</p>
</blockquote>
<pre>std::size_t <a name="hash_value">hash_value</a> (const path&amp; p);</pre>
<blockquote>
  <p><i>Returns:</i> A hash value for the path <code>p</code>. If
  for two paths, <code>p1 == p2</code> then
  <code>hash_value(p1) == hash_value(p2)</code>.</p>
  <p>This allows paths to be used with
  <a href="../../../functional/hash/index.html">Boost.Hash</a>.</p>
</blockquote>
<pre>bool operator&lt; (const path&amp; lhs, const path&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>return lexicographical_compare(lhs.begin(), lhs.end(), 
  rhs.begin(), rhs.end())</code>.</p>
</blockquote>
<pre>bool operator&lt;=(const path&amp; lhs, const path&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>!(rhs &lt; lhs)</code>.</p>
</blockquote>
<pre>bool operator&gt; (const path&amp; lhs, const path&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>rhs &lt; lhs</code>.</p>
</blockquote>
<pre>bool operator&gt;=(const path&amp; lhs, const path&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>!(lhs &lt; rhs)</code>.</p>
</blockquote>
<pre>bool operator==(const path&amp; lhs, const path&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>!(lhs &lt; rhs) &amp;&amp; !(rhs &lt; lhs)</code>.</p>
  <p>[<i>Note:</i> Actual implementations may use an equivalent, but more 
  efficient, algorithm. <i>--end note</i>]</p>
  <p>[<i>Note:</i> <a name="Path-equality">Path equality</a> and path 
  equivalence have different semantics.</p>
  <p>Equality is determined by the <code>path</code> 
  non-member <code>operator==</code>, which considers the two path's lexical 
  representations only. Thus <code>path(&quot;foo&quot;) == &quot;bar&quot;</code> is never 
  <code>true</code>.</p>
  <p>Equivalence is determined by the <a href="#equivalent"><code>equivalent()</code></a> 
  non-member function, which determines if two paths <a href="#Path">resolve</a> to the same file system entity. 
  Thus <code>equivalent(&quot;foo&quot;, &quot;bar&quot;)</code> will be <code>true</code> 
  when both paths resolve to the same file.</p>
  <p>Programmers wishing to determine if two paths are &quot;the same&quot; must decide if 
  &quot;the same&quot; means &quot;the same representation&quot; or &quot;resolve to the same actual 
  file&quot;, and choose the appropriate function accordingly. <i>
  -- end note</i>]</p>
</blockquote>
<pre>bool operator!=(const path&amp; lhs, const path&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>!(lhs == rhs)</code>.</p>
</blockquote>
<pre>path operator/ (const path&amp; lhs, const path&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>path(lhs) /= rhs</code>.</p>
</blockquote>
<h3> <a name="path-non-member-operators"><code><font size="4">path</font></code></a><a name="path-inserter-extractor"> inserter 
  and extractor</a></h3>
<p> The inserter and extractor delimit the string with double-quotes (<code>&quot;</code>) 
to ensure that paths with embedded spaces will round trip correctly. Ampersand (<code>&amp;</code>) 
is used as an escape character, so the path can itself contain double quotes.</p>
<pre>template &lt;class Char, class Traits&gt;
std::basic_ostream&lt;Char, Traits&gt;&amp; operator&lt;&lt;(std::basic_ostream&lt;Char, Traits&gt;&amp; os,
                                             const path&amp; p)
</pre>
<blockquote>
  <p><i>Effects:</i>&nbsp;
  <code>os &lt;&lt; <a href="../../../io/doc/quoted_manip.html">
  boost::io::quoted</a>(p.string&lt;std::basic_string&lt;Char&gt;&gt;(), static_cast&lt;Char&gt;('&amp;'));</code></p>
  <p><i>Returns:</i>
   <code>os</code></p>
</blockquote>
<pre>template &lt;class Char, class Traits&gt;
inline std::basic_istream&lt;Char, Traits&gt;&amp; operator&gt;&gt;(std::basic_istream&lt;Char, Traits&gt;&amp; is,
                                                    path&amp; p)
</pre>
<blockquote>
  <p><i>Effects:&nbsp; </i>
      <code>&nbsp;std::basic_string&lt;Char&gt; str;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; is &gt;&gt;
  <a href="../../../io/doc/quoted_manip.html">boost::io::quoted</a>(str, 
  static_cast&lt;Char&gt;('&amp;'));<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; p = str;</code></p>
  <p><i>Returns:</i>
   <code>is</code></p>
  </blockquote>
<h3><a name="Class-filesystem_error">Class <code>filesystem_error</code></a></h3>
<pre>namespace std { namespace tbd { namespace filesystem {

      class filesystem_error : public system_error
      {
      public:
        filesystem_error();
        filesystem_error(const filesystem_error&amp;);
        <a href="#filesystem_error-2-arg">filesystem_error</a>(const std::string&amp; what_arg,
          system::error_code ec);
        <a href="#filesystem_error-3-arg">filesystem_error</a>(const std::string&amp; what_arg,
          const path&amp; p1, system::error_code ec);
        <a href="#filesystem_error-4-arg">filesystem_error</a>(const std::string&amp; what_arg,
          const path&amp; p1, const path&amp; p2, system::error_code ec);

        filesystem_error&amp; filesystem_error(const filesystem_error&amp;);
       ~filesystem_error();

        filesystem_error&amp; operator=(const filesystem_error&amp;);

        const path&amp; <a href="#filesystem_error-path1">path1</a>() const;
        const path&amp; <a href="#filesystem_error-path2">path2</a>() const;

        const char * <a href="#filesystem_error-what">what</a>() const;
      };
} } }  // namespaces std::tbd::filesystem</pre>
<p>The class template <code>filesystem_error</code> defines the type of 
objects thrown as exceptions to report file system errors from functions described in this 
Clause.</p>
<h4> <a name="filesystem_error-members"> <code>filesystem_error</code> members</a></h4>
<pre><a name="filesystem_error-2-arg">filesystem_error</a>(const std::string&amp; what_arg, error_code ec);</pre>
<blockquote>
  <p><i>Postcondition:</i></p>
  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="46%">
    <tr>
      <td width="18%"><b>Expression</b></td>
      <td width="82%"><b>Value</b></td>
    </tr>
    <tr>
      <td width="18%" bgcolor="#FFFFFF"><code>
      runtime_error::what()</code></td>
      <td width="82%" bgcolor="#FFFFFF">
      <code><i>what_arg</i>.c_str()</code></td>
    </tr>
    <tr>
      <td width="18%"><code>code()</code></td>
      <td width="82%"><code>ec</code></td>
    </tr>
    <tr>
      <td width="18%"><code>path1().empty()</code></td>
      <td width="82%"><code>true</code></td>
    </tr>
    <tr>
      <td width="18%"><code>path2().empty()</code></td>
      <td width="82%"><code>true</code></td>
    </tr>
  </table>
</blockquote>
<pre><a name="filesystem_error-3-arg">filesystem_error</a>(const std::string&amp; what_arg, const path_type&amp; p1, error_code ec);</pre>
<blockquote>
  <p><i>Postcondition:</i></p>
  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="46%">
    <tr>
      <td width="18%"><b>Expression</b></td>
      <td width="82%"><b>Value</b></td>
    </tr>
    <tr>
      <td width="18%" valign="top"><code>
      runtime_error::what()</code></td>
      <td width="82%">
      <code><i>what_arg</i>.c_str()</code></td>
    </tr>
    <tr>
      <td width="18%" valign="top"><code>code()</code></td>
      <td width="82%"><code>ec</code></td>
    </tr>
    <tr>
      <td width="18%" valign="top"><code>path1()</code></td>
      <td width="82%">Reference to stored copy of
       <code>p1</code></td>
    </tr>
    <tr>
      <td width="18%" valign="top"><code>path2().empty()</code></td>
      <td width="82%"><code>true</code></td>
    </tr>
  </table>
</blockquote>
<pre><a name="filesystem_error-4-arg">filesystem_error</a>(const std::string&amp; what_arg, const path_type&amp; p1, const path_type&amp; p2, error_code ec);</pre>
<blockquote>
  <p><i>Postcondition:</i></p>
  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="46%">
    <tr>
      <td width="18%"><b>Expression</b></td>
      <td width="82%"><b>Value</b></td>
    </tr>
    <tr>
      <td width="18%"><code>
      runtime_error::what()</code></td>
      <td width="82%">
      <u>
      <code><i>w</i></code></u><code><i>hat_arg</i>.c_str()</code></td>
    </tr>
    <tr>
      <td width="18%"><code>code()</code></td>
      <td width="82%"><code>ec</code></td>
    </tr>
    <tr>
      <td width="18%"><code>path1()</code></td>
      <td width="82%">Reference to stored copy of
       <code>p1</code></td>
    </tr>
    <tr>
      <td width="18%"><code>path2()</code></td>
      <td width="82%">Reference to stored copy of
       <code>p2</code></td>
    </tr>
  </table>
</blockquote>
<pre>const path&amp; <a name="filesystem_error-path1">path1</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> Reference to copy of <code>p1</code> stored by the 
  constructor, or, if none, an empty path.</p>
</blockquote>
<pre>const path&amp; <a name="filesystem_error-path2">path2</a>() const;</pre>
<blockquote>
  <p><i>Returns:</i> Reference to copy of <code>p2</code> stored by the 
  constructor, or, if none, an empty path.</p>
</blockquote>
<pre>const char* <a name="filesystem_error-what">what</a>() const;</pre>
<blockquote>
  <p><i>Returns: </i>A string containing <code>runtime_error::what()</code>. The exact format is unspecified. 
  Implementations are encouraged but not required to include <code>
  path1.native_string()</code>if not empty, <code>path2.native_string()</code>if 
  not empty, and <code>system_error::what()</code> strings in the returned 
  string.</p>
</blockquote>
<h3><a name="Enum-file_type">Enum file_type</a></h3>
<p>This enum specifies constants uses to identify file types.</p>
<table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111">
  <tr>
    <td><b>Constant Name</b></td>
    <td><b>Meaning</b></td>
  </tr>
  <tr>
    <td><code>status_error</code></td>
    <td>An error occurred while trying to obtain the status of the file. The 
    file simply not being found is <b><u>not</u></b> considered a status error.
    </td>
  </tr>
  <tr>
    <td><code>file_not_found</code></td>
    <td>The file could not be found</td>
  </tr>
  <tr>
    <td><code>regular_file</code></td>
    <td>Regular file</td>
  </tr>
  <tr>
    <td><code>directory_file</code></td>
    <td>Directory file</td>
  </tr>
  <tr>
    <td><code>symlink_file</code></td>
    <td>Symbolic link file</td>
  </tr>
  <tr>
    <td><code>block_file</code></td>
    <td>Block special file</td>
  </tr>
  <tr>
    <td><code>character_file</code></td>
    <td>Character special file</td>
  </tr>
  <tr>
    <td><code>fifo_file</code></td>
    <td>FIFO or pipe file</td>
  </tr>
  <tr>
    <td><code>socket_file</code></td>
    <td>Socket file</td>
  </tr>
  <tr>
    <td><code>type_unknown</code></td>
    <td>The file exists, but it is of a system specific type not covered by any 
    of the above cases.</td>
  </tr>
</table>
<h3><a name="Enum-perms">Enum perms</a></h3>
<p>This enum specifies bitmask constants uses to identify file 
permissions. The POSIX standard specifies actual values, and those values have 
been adopted here because they are very familiar and ingrained for many POSIX 
users.</p>
<blockquote>
<p>Caution: Operating systems do not always support permissions as described in 
the table.</p>
<p>There is much variation in the meaning of <code><a href="#sticky_bit">
sticky_bit</a></code>; do not use it unless you understand what it means for 
your operating system.</p>
<p>There is much variation in how operating systems treat symlinks. See <code>
<a href="#symlink_perms">symlink_perms</a></code>.</p>
<p>Windows: All permissions except write are currently ignored. There is only a 
single write permission; setting write permission for owner, group, or others 
sets write permission for all, and removing write permission for owner, group, 
or others removes write permission for all. </p>
</blockquote>
<table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111">
  <tr>
    <td><b>Name</b></td>
    <td align="center"><b>Value<br>
    (octal)</b></td>
    <td align="center"><b>POSIX<br>
    macro</b></td>
    <td><b>Definition or notes</b></td>
  </tr>

<tr><td>
  <p dir="ltr"><code>no_perms</code></td><td><code>0</code></td><td></td>
  <td>There are no permissions set for the file. Note: <code>file_not_found</code> is 
  <code>no_perms</code> rather than <code>perms_not_known</code></td>
</tr>
<tr><td><code>owner_read</code></td><td><code>0400</code></td><td> <code>S_IRUSR</code></td>
  <td> Read permission, owner</td>
</tr>
<tr><td><code>owner_write</code></td><td><code>0200</code></td><td> <code>S_IWUSR</code></td>
  <td> Write permission, owner</td>
</tr>
<tr><td><code>owner_exe</code></td><td><code>0100</code></td><td>  <code>S_IXUSR</code></td>
  <td> Execute/search permission, owner</td>
</tr>
<tr><td><code>owner_all</code></td><td><code>0700</code></td><td>  <code>S_IRWXU</code></td>
  <td> Read, write, execute/search by owner; <code>owner_read | owner_write | owner_exe</code></td>
</tr>
<tr><td><code>group_read</code></td><td><code>040</code></td><td>  <code>S_IRGRP</code></td>
  <td> Read permission, group</td>
</tr>
<tr><td><code>group_write</code></td><td><code>020</code></td><td> <code>S_IWGRP</code></td>
  <td> Write permission, group</td>
</tr>
<tr><td><code>group_exe</code></td><td><code>010</code></td><td>   <code>S_IXGRP</code></td>
  <td> Execute/search permission, group</td>
</tr>
<tr><td><code>group_all</code></td><td><code>070</code></td><td>   <code>S_IRWXG</code></td>
  <td> Read, write, execute/search by group; <code>group_read | group_write | 
  group_exe</code></td>
</tr>
<tr><td><code>others_read</code></td><td><code>04</code></td><td>  <code>S_IROTH</code></td>
  <td> Read permission, others</td>
</tr>
<tr><td><code>others_write</code></td><td><code>02</code></td><td> <code>S_IWOTH</code></td>
  <td> Write permission, others</td>
</tr>
<tr><td><code>others_exe</code></td><td><code>01</code></td><td>   <code>S_IXOTH</code></td>
  <td> Execute/search permission, others</td>
</tr>
<tr><td><code>others_all</code></td><td><code>07</code></td><td>   <code>S_IRWXO</code></td>
  <td>Read, write, execute/search by others; <code>others_read | others_write | others_exe</code></td>
</tr>
<tr><td><code>all_all</code></td><td><code>0777</code></td><td> </td><td><code>owner_all | group_all | others_all</code></td>
</tr>
<tr><td><code>set_uid_on_exe</code></td><td><code>04000</code></td><td> <code>S_ISUID</code></td>
  <td> Set-user-ID on execution</td>
</tr>
<tr><td><code>set_gid_on_exe</code></td><td><code>02000</code></td><td> <code>S_ISGID</code></td>
  <td> Set-group-ID on execution</td>
</tr>
<tr><td><code><a name="sticky_bit">sticky_bit</a> </code>    </td><td><code>01000</code></td><td> <code>S_ISVTX</code></td>
  <td> Meaning varies; see <a href="http://en.wikipedia.org/wiki/Sticky_bit">http:en.wikipedia.org/wiki/Sticky_bit</a></td>
</tr>
<tr><td><code><a name="perms_mask">perms_mask</a></code></td><td><code>07777</code></td><td> &nbsp;</td>
  <td><code>all_all | set_uid_on_exe | set_gid_on_exe | sticky_bit</code></td>
</tr>
<tr><td><code>perms_not_known</code></td><td><code>0xFFFF</code></td><td></td><td> 
  The permissions are not known, such as when a <code>file_status</code> object 
  is created without specifying the permissions</td>
</tr>
<tr><td>
  <p dir="ltr"><code>add_perms</code></td><td><code>0x1000</code></td><td></td><td>
  <p dir="ltr"><code>permissions()</code> adds the argument permission bits to the 
  file's current bits</td>
</tr>
<tr><td><code>remove_perms</code></td><td><code>0x2000</code></td><td></td><td>
  <code>permissions()</code> removes the argument permission bits from the 
  file's current bits</td>
</tr>
<tr><td><code><a name="symlink_perms">symlink_perms</a></code></td><td><code>0x4000</code></td><td></td><td>
  On POSIX <code>permissions()</code> resolves symlinks unless <code>symlink_perms</code> 
  is specified. 
  Meaningless on Windows as <code>permissions()</code> never resolves symlinks. 
  Meaningless on Mac OS X and some other BSD systems as <code>permissions()</code> 
  always resolves symlinks. Get over it.</td>
</tr>

</table>
<h3><a name="file_status">Class file_status</a></h3>
<pre>namespace std { namespace tbd { namespace filesystem {

      class file_status
      {
      public:

        // <a href="#file_status-constructors">constructors</a>
        file_status() noexcept;
        explicit file_status(<a href="#file_type">file_type</a> ft, <a href="#Enum-perms">perms</a> prms = perms_not_known) noexcept;

        // compiler generated
        file_status(const file_status&amp;) noexcept;
        file_status&amp; operator=(const file_status&amp;) noexcept;
       ~file_status() noexcept;

        // <a href="#file_status-observers">observers</a>
        <a href="#file_type">file_type</a>  type() const noexcept;
        <a href="#Enum-perms">perms</a>      permissions() const noexcept;

        // <a href="#file_status-modifiers">modifiers</a>
        void       type(<a href="#file_type">file_type</a> ft) noexcept;
        void       permissions(<a href="#Enum-perms">perms</a> prms) noexcept;
      };
} } }  // namespaces std::tbd::filesystem</pre>
<p>An object of type <code>file_status</code> stores information about the type 
and permissions of a file.</p>
<h4 dir="ltr"><a name="file_status-constructors"><code>file_status</code> 
constructors</a></h4>
<pre>explicit file_status() noexcept;</pre>
<blockquote>
  <p><i>Postconditions:</i> <code>type() == status_error</code>, <code>
  permissions() == perms_not_known</code>.</p>
</blockquote>
<pre>explicit file_status(<a href="#file_type">file_type</a> ft, <a href="#Enum-perms">perms</a> prms = perms_not_known) noexcept;</pre>
<blockquote>
  <p><i>Postconditions:</i> <code>type() == ft</code>, <code>permissions() == 
  prms</code>.</p>
</blockquote>
  <h4 dir="ltr"><a name="file_status-observers"><code>file_status</code> 
  observers</a></h4>
<pre><a href="#file_type">file_type</a> type() const noexcept;</pre>
<blockquote>
  <p><i>Returns: </i>The value of <code>type()</code> specified by the <i>
  postconditions</i> of the most recent call to a constructor, operator=, or
  <code>type(file_type)</code> function.</p>
</blockquote>
<pre><a href="#Enum-perms">perms</a> permissions() const noexcept;</pre>
<blockquote>
  <p><i>Returns: </i>The value of <code>permissions()</code> specified by the <i>
  postconditions</i> of the most recent call to a constructor, operator=, or
  <code>permissions(perms)</code> function.</p>
</blockquote>
<h4 dir="ltr"><a name="file_status-modifiers"><code>file_status</code> modifiers</a></h4>
<pre>void type(<a href="#file_type">file_type</a> ft) noexcept;</pre>
<blockquote>
  <p dir="ltr"><i>Postconditions:</i> <code>type() == ft</code>.</p>
</blockquote>
<pre>void permissions(<a href="#Enum-perms">perms</a> prms) noexcept;</pre>
<blockquote>
  <p dir="ltr"><i>Postconditions:</i> <code>permissions() == prms</code>.</p>
</blockquote>
<h3><a name="Class-directory_entry">Class <code>directory_entry</code></a></h3>
<div dir="ltr">
<pre>namespace std { namespace tbd { namespace filesystem {

      class directory_entry
      {
      public:

        // <a href="#directory_entry-constructors">constructors</a> and destructor
        directory_entry();
        directory_entry(const directory_entry&amp;);
        explicit directory_entry(const path_type&amp; p, file_status st=file_status(),
          file_status symlink_st=file_status());
       ~directory_entry(); 

        // <a href="#directory_entry-modifiers">modifiers</a>
        directory_entry&amp; operator=(const directory_entry&amp;);
        void assign(const path_type&amp; p, file_status st=file_status(),
          file_status symlink_st=file_status());
        void replace_filename(const path&amp; p, file_status st=file_status(),
          file_status symlink_st=file_status());

        // <a href="#directory_entry-observers">observers</a>
        const path&amp;  path() const;
        file_status  status() const;
        file_status  status(system::error_code&amp; ec) const;
        file_status  symlink_status() const;
        file_status  symlink_status(system::error_code&amp; ec) const;

        bool operator&lt; (const directory_entry&amp; rhs);
        bool operator==(const directory_entry&amp; rhs); 
        bool operator!=(const directory_entry&amp; rhs); 
        bool operator&lt; (const directory_entry&amp; rhs);
        bool operator&lt;=(const directory_entry&amp; rhs);
        bool operator&gt; (const directory_entry&amp; rhs);
        bool operator&gt;=(const directory_entry&amp; rhs);
      private:
        path_type            m_path;           // for exposition only
        mutable file_status  m_status;         // for exposition only; stat()-like
        mutable file_status  m_symlink_status; // for exposition only; lstat()-like
      };

} } }  // namespaces std::tbd::filesystem</pre>
</div>
<p>A <code>directory_entry</code> object stores a <code>path object</code>, 
a <code>file_status</code> object for non-symbolic link status, and a <code>
file_status</code> object for symbolic link status. The <code>file_status</code> 
objects act as value caches.</p>
<blockquote>
<p>[<i>Note:</i> Because <code>status()</code>on a pathname may be a very expensive operation, 
some operating systems provide status information as a byproduct of directory 
iteration. Caching such status information can result is significant time savings. Cached and 
non-cached results may differ in the presence of file system races. <i>-- end note</i>]</p>
<p><span style="background-color: #E0E0E0"><i>Actual cold-boot timing of iteration over 
a directory with 15,047 entries was six seconds for non-cached status queries 
versus one second for cached status queries. Windows XP, 3.0 GHz processor, with 
a moderately fast hard-drive. Similar speedups are expected on Linux and BSD-derived 
systems that provide status as a by-product of directory iteration.</i></span></p>
</blockquote>
<h4> <a name="directory_entry-constructors"> <code>directory_entry </code>constructors</a></h4>
<pre>directory_entry();</pre>
<blockquote>
  <p><i>Postcondition:</i></p>
  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="36%">
    <tr>
      <td width="18%"><b>Expression</b></td>
      <td width="82%"><b>Value</b></td>
    </tr>
    <tr>
      <td width="18%"><code>path().empty()</code></td>
      <td width="82%"><code>true</code></td>
    </tr>
    <tr>
      <td width="18%"><code>status()</code></td>
      <td width="82%"><code>file_status()</code></td>
    </tr>
    <tr>
      <td width="18%"><code>symlink_status()</code></td>
      <td width="82%"><code>file_status()</code></td>
    </tr>
  </table>
</blockquote>
<pre>explicit directory_entry(const path_type&amp; p, file_status st=file_status(), file_status symlink_st=file_status());</pre>
<blockquote>
  <p><i>Postcondition:</i></p>
  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="36%">
    <tr>
      <td width="18%"><b>Expression</b></td>
      <td width="82%"><b>Value</b></td>
    </tr>
    <tr>
      <td width="18%"><code>path()</code></td>
      <td width="82%"><code>p</code></td>
    </tr>
    <tr>
      <td width="18%"><code>status()</code></td>
      <td width="82%"><code>st</code></td>
    </tr>
    <tr>
      <td width="18%"><code>symlink_status()</code></td>
      <td width="82%"><code>symlink_st</code></td>
    </tr>
  </table>
</blockquote>
<h4> <a name="directory_entry-modifiers"> <code>directory_entry </code>modifiers</a></h4>
<pre>void assign(const path_type&amp; p, file_status st=file_status(), file_status symlink_st=file_status());</pre>
<blockquote>
  <p><i>Postcondition:</i></p>
  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="36%">
    <tr>
      <td width="18%"><b>Expression</b></td>
      <td width="82%"><b>Value</b></td>
    </tr>
    <tr>
      <td width="18%"><code>path()</code></td>
      <td width="82%"><code>p</code></td>
    </tr>
    <tr>
      <td width="18%"><code>status()</code></td>
      <td width="82%"><code>st</code></td>
    </tr>
    <tr>
      <td width="18%"><code>symlink_status()</code></td>
      <td width="82%"><code>symlink_st</code></td>
    </tr>
  </table>
</blockquote>
<pre>void replace_filename(const path&amp; p, file_status st=file_status(), file_status symlink_st=file_status());</pre>
<blockquote>
  <p><i>Postcondition:</i></p>
  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="43%">
    <tr>
      <td width="18%"><b>Expression</b></td>
      <td width="82%"><b>Value</b></td>
    </tr>
    <tr>
      <td width="18%"><code>path()</code></td>
      <td width="82%"><code>path().branch() / s</code></td>
    </tr>
    <tr>
      <td width="18%"><code>status()</code></td>
      <td width="82%"><code>st</code></td>
    </tr>
    <tr>
      <td width="18%"><code>symlink_status()</code></td>
      <td width="82%"><code>symlink_st</code></td>
    </tr>
  </table>
</blockquote>
<h4> <a name="directory_entry-observers"> <code>directory_entry</code> observers</a></h4>
<pre>const path&amp; path() const;</pre>
<blockquote>
  <p><i>Returns:</i> <code>m_path</code></p>
</blockquote>
<pre>file_status status() const;
file_status status(system::error_code&amp; ec) const;</pre>
<blockquote>
<p><i>Effects:</i> 
As if,</p>
  <blockquote>
    <pre>if ( !status_known( m_status ) )
{
  if ( status_known(m_symlink_status) &amp;&amp; !is_symlink(m_symlink_status) )
    { m_status = m_symlink_status; }
  else { m_status = status(m_path<i>[, ec]</i>); }
}</pre>
  </blockquote>
  <p><i>Returns:</i> <code>m_status</code></p>
  
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  
</blockquote>
<pre>file_status  symlink_status() const;
file_status  symlink_status(system::error_code&amp; ec) const;</pre>
<blockquote>
<p>
  <i>Effects:</i> 
As if,</p>
  <blockquote>
    <pre>if ( !status_known( m_symlink_status ) )
{
  m_symlink_status = symlink_status(m_path<i>[, ec]</i>);
}</pre>
  </blockquote>
  <p><i>Returns:</i> <code>
  m_symlink_status</code></p>
  
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  
</blockquote>
<pre>bool operator==(const directory_entry&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>m_path == 
  rhs.m_path</code>.</p>
</blockquote>
<pre>bool operator!=(const directory_entry&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>m_path != 
  rhs.m_path</code>.</p>
</blockquote>
<pre>bool operator&lt; (const directory_entry&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>m_path &lt; 
  rhs.m_path</code>.</p>
</blockquote>
<pre>bool operator&lt;=(const directory_entry&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>m_path &lt;= 
  rhs.m_path</code>.</p>
</blockquote>
<pre>bool operator&gt; (const directory_entry&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>m_path &gt; 
  rhs.m_path</code>.</p>
</blockquote>
<pre>bool operator&gt;=(const directory_entry&amp; rhs);</pre>
<blockquote>
  <p><i>Returns:</i> <code>m_path &gt;= 
  rhs.m_path</code>.</p>
</blockquote>
<h3><a name="Class-directory_iterator">Class <code>directory_iterator</code></a></h3>
<p>Objects of type <code>directory_iterator</code> provide standard library 
compliant iteration over the contents of a directory. Also see class <code>
<a href="#Class-recursive_directory_iterator">recursive_directory_iterator</a></code>.</p>
<pre>namespace std { namespace tbd { namespace filesystem {

      class directory_iterator
      {
      public:
        // <a href="#directory_iterator-members">member functions</a>

        directory_iterator() noexcept;  // creates the &quot;end&quot; iterator
        directory_iterator(const directory_iterator&amp;);
        explicit directory_iterator(const path&amp; p);
        directory_iterator(const path&amp; p, system::error_code&amp; ec);
       ~directory_iterator();

        directory_iterator&amp; operator=(const directory_iterator&amp;);

        directory_iterator&amp; operator++();
        directory_iterator&amp; increment(system::error_code&amp; ec);

        // other members as required by
        //  C++ Std, 24.1.1 Input iterators [input.iterators]
      };

} } }  // namespaces std::tbd::filesystem</pre>
<p> <code>directory_iterator</code> satisfies the requirements of an 
input iterator (C++ Std, 24.2.1, Input iterators [input.iterators]).</p>
<p>A <code>directory_iterator</code> reads successive elements from the directory for 
which it was constructed, as if by calling <i>POSIX</i>
<code>
<a href="http://www.opengroup.org/onlinepubs/000095399/functions/readdir_r.html">readdir_r()</a></code>. After a <code>directory_iterator</code> is constructed, and every time 
<code>operator++</code> is called, 
it reads a directory element and stores information about it in a object of type <code>
<a href="#Class-directory_entry">directory_entry</a></code>. 
<code>operator++</code> is not equality preserving; that is, <code>i == j</code> does not imply that
<code>++i == ++j</code>. </p>
<blockquote>
<p>[<i>Note:</i> The practical consequence of not preserving equality is that directory iterators 
can only be used for single-pass algorithms. <i>--end note</i>]</p>
</blockquote>
<p>If the end of the directory elements is reached, the iterator becomes equal to 
the end iterator value. The constructor <code>directory_iterator()</code> 
with no arguments always constructs an end iterator object, which is the only 
legitimate iterator to be used for the end condition. The result of <code>
operator*</code> on an end iterator is not defined. For any other iterator value 
a <code>const directory_entry&amp;</code> is returned. The result of
<code>operator-&gt;</code> on an end iterator is not defined. For any other iterator value a <code>const directory_entry*</code> is 
returned. </p>
<p>Two end iterators are always equal. An end iterator is not equal to a non-end 
iterator.</p>
<blockquote>
<p><i><span style="background-color: #E0E0E0">The above wording is based on the 
Standard Library's istream_iterator wording.</span></i></p>
</blockquote>
<p>The result of calling the <code>path()</code> member of the <code>
directory_entry</code> object obtained by dereferencing a <code>
directory_iterator</code> is a reference to a <code>path</code> 
object composed of the directory argument from which the iterator was 
constructed with filename of the directory entry appended as if by <code>
operator/=</code>. </p>
<p>Directory iteration shall not yield directory entries for the current (<i>dot</i>) 
and parent (<i>dot dot</i>) directories.</p>
<p>The order of directory entries obtained by dereferencing successive 
increments of a <code>directory_iterator</code> is unspecified.</p>
<blockquote>
<p>[<i>Note:</i> Programs performing directory iteration may wish to test if the 
path obtained by dereferencing a directory iterator actually exists. It could be 
a
symbolic link to a non-existent file. Programs recursively 
walking directory trees for purposes of removing and renaming entries may wish 
to avoid following symbolic links.</p>
<p>If a file  is removed from or added to a directory after the 
construction of a <code>directory_iterator</code> for the directory, it is 
unspecified whether or not subsequent incrementing of the iterator will ever 
result in an iterator whose value is the removed or added directory entry. See
<i>POSIX</i>
<code>
<a href="http://www.opengroup.org/onlinepubs/000095399/functions/readdir_r.html">readdir_r()</a></code>. <i>
--end note</i>]</p>
</blockquote>
<h4><a name="directory_iterator-members"><code>directory_iterator</code> members</a></h4>

<p><code><a name="directory_iterator-default-ctor">directory_iterator</a>() 
noexcept;</code></p>

<blockquote>

<p><i>Effects:</i> Constructs the end iterator.</p>

</blockquote>

<pre><code>explicit <a name="directory_iterator-ctor-path">directory_iterator</a>(</code>const path&amp; p<code>);
directory_iterator(</code>const path&amp; p, system::error_code&amp; ec<code>);</code></pre>
<blockquote>

<p><i>Effects:</i> Constructs a iterator representing the first 
entry in the directory <code>p</code> resolves to, if any; otherwise, the end iterator.</p>

<p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>

<p>[<i>Note:</i> To iterate over the current directory, use <code>
directory_iterator(&quot;.&quot;)</code> rather than <code>directory_iterator(&quot;&quot;)</code>.
<i>-- end note</i>]</p>
</blockquote>
<pre>directory_iterator&amp; <a name="directory_iterator-increment">operator++</a>();
directory_iterator&amp; increment(system::error_code&amp; ec);</pre>
<blockquote>

<p><i>Effects:</i> As specified by the C++ Standard, 24.1.1 Input iterators [input.iterators]</p>

<p><i>Returns:</i> <code>*this</code>.</p>

<p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>

</blockquote>
<h3><a name="Class-recursive_directory_iterator">Class <code>recursive_directory_iterator</code></a></h3>
<p>Objects of type <code>recursive_directory_iterator</code> provide standard library 
compliant iteration over the contents of a directory, including recursion into 
its sub-directories.</p>
<pre>namespace std { namespace tbd { namespace filesystem {

      class recursive_directory_iterator :
        public iterator&lt;input_iterator_tag, directory_entry&gt;
      {
      public:

        // constructors and destructor
        recursive_directory_iterator() noexcept;
        recursive_directory_iterator(const recursive_directory_iterator&amp;);
        explicit recursive_directory_iterator(const path&amp; p,
          <a href="#symlink_option">symlink_option</a> opt = symlink_option::none);
        recursive_directory_iterator(const path&amp; p,
          <a href="#symlink_option">symlink_option</a> opt, system::error_code&amp; ec);
        recursive_directory_iterator(const path&amp; p, system::error_code&amp; ec);
       ~recursive_directory_iterator();

        // observers
        int level() const noexcept;
        bool no_push<code>_pending</code>() const noexcept;

        // modifiers
        recursive_directory_iterator&amp; operator=(const recursive_directory_iterator&amp;);

        recursive_directory_iterator&amp; operator++();
        recursive_directory_iterator&amp; increment(system::error_code&amp; ec);

        void pop();
        void no_push(bool value=true);

        // other members as required by
        //  C++ Std, Input iterators [input.iterators]

      private:
<i><b>        // actual data members will probably be stored in a shared object,
        // or some similar mechanism, to achieve the required input iterator
        // copy semantics
</b></i>        int            m_level; <b><i>   // for exposition only</i></b>
        bool           m_no_<code>push</code>;  <i><b>// for exposition only
        </b></i><a href="#symlink_option">symlink_option</a> m_options;  <i><b>// for exposition only</b></i>
      };

} } }  // namespaces std::tbd::filesystem</pre>

<p>The behavior of a <code>recursive_directory_iterator</code> is the same 
as a <code>directory_iterator</code> unless otherwise specified.</p>
<ul>
  <li>Incrementing a <code>recursive_directory_iterator</code> pointing to a 
  directory causes that directory itself to be iterated ovee, as specified by 
  the <code>operator++</code> and <code>increment</code> functions.<br>
&nbsp;</li>
  <li>When a <code>recursive_directory_iterator</code> reaches the end of the directory currently being iterated 
  over, or when <code>pop()</code> is called, <code>m_level</code> is 
  decremented, and iteration of the parent directory continues.</li>
</ul>
<pre>recursive_directory_iterator() noexcept;</pre>
<blockquote>

<p><i>Effects:</i> Constructs the end iterator.</p>

</blockquote>

<pre>explicit recursive_directory_iterator(const path&amp; p, <a href="#symlink_option">symlink_option</a> opt = symlink_option::none);
recursive_directory_iterator(const path&amp; p, <a href="#symlink_option">symlink_option</a> opt, system::error_code&amp; ec);
recursive_<code>directory_iterator(</code>const path&amp; p, system::error_code&amp; ec<code>);</code></pre>
<blockquote>

<p><i>Effects:</i>&nbsp; Constructs a iterator representing the first 
entry in the directory <code>p</code> resolves to, if any; otherwise, the end iterator.</p>

<p dir="ltr"><i>Postcondition: </i>Unless the end iterator was constructed,<i> </i>
<code>level() == 0 &amp;&amp; no_push_pending() == false &amp;&amp; m_options == opt</code>. 
For the signature without a <code>symlink_option</code> argument, <code>opt</code> 
is assumed to be <code>symlink_option::none</code>.</p>

<p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>

<p>[<i>Note:</i> To iterate over the current directory, use <code>recursive_directory_iterator(&quot;.&quot;)</code> rather than
<code>recursive_directory_iterator(&quot;&quot;)</code>.
<i>-- end note</i>]</p>

<p>[<i>Note:</i> By default, <code>recursive_directory_iterator</code> does not 
follow directory symlinks. To follow directory symlinks, specify <code>opt</code> 
as <code>symlink_option::recurse</code>
<i>-- end note</i>]</p>
</blockquote>
<pre>int level() const noexcept;</pre>
<blockquote>
  <p><i>Requires:</i> <code>*this != recursive_directory_iterator()</code>.</p>
  <p><i>Returns:</i> <code>m_level</code>.</p>
</blockquote>
<pre>bool <code>no_push_pending</code>() const noexcept;</pre>
<blockquote>
  <p><i>Requires:</i> <code>*this != recursive_directory_iterator()</code>.</p>
  <p><i>Returns:</i> <code>m_no_push</code>.</p>
</blockquote>
<pre><code>recursive_directory_iterator</code>&amp; <a name="recursive_directory_iterator-increment">operator++</a>();
recursive_directory_iterator&amp; increment(system::error_code&amp; ec);</pre>
<blockquote>

<p><i>Effects:</i> As specified by the C++ Standard, 24.1.1 Input iterators [input.iterators], 
except:</p>

<ul>
  <li dir="ltr">

<p dir="ltr">if <code>!no_push_pending() &amp;&amp; is_directory(this-&gt;status()) 
&amp;&amp; (!is_symlink(this-&gt;symlink_status()) || (m_options 
&amp; symlink_option::recurse) != 0)</code> then&nbsp; <code>m_level</code> 
is incremented and directory <code>(*this)-&gt;path()</code> is recursively iterated into.<br>
&nbsp;</p>

  </li>
  <li>if there are no more directory entries at this level then <code>m_level</code> 
is decremented and iteration of the parent directory resumes.</li>
</ul>

<p><i>Postcondition:</i> <code>no_push_pending() == false</code>.</p>

<p><i>Returns:</i> <code>*this</code>.</p>

<p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>

</blockquote>
<pre>void pop();</pre>
<blockquote>
  <p><i>Requires:</i> <code>*this != recursive_directory_iterator()</code>.</p>
  <p><i>Effects:</i> If <code>level() == 0</code>, set <code>*this</code> to <code>recursive_directory_iterator()</code>. 
  Otherwise, <code>--m_level</code>, cease iteration of the directory currently being 
  iterated over, and continue iteration over the parent directory.</p>
</blockquote>
<pre>void no_push(bool value=true);</pre>
<blockquote>
  <p><i>Requires:</i> <code>*this != recursive_directory_iterator()</code>.</p>
<p><i>Postcondition:</i> <code>no_push_pending() == value</code>.</p>
  <p>[<i>Note:</i> <code>no_push()</code> is used to prevent 
  unwanted recursion into a directory. <i>--end note</i>]</p>
</blockquote>
<h3><a name="Operational-functions">Operational functions</a></h3>
<p>Operational functions query or modify files, including directories, in external 
storage.</p>
<p>Operational functions access a file by resolving an 
object of class <code>path</code> to a particular file in a file hierarchy. The 
path is resolved as if by the <i>POSIX</i>
<a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap04.html#tag_04_11">
Pathname Resolution</a> mechanism.</p>
<p>[<i>Note: </i>Because hardware failures, network failures,
<a href="#Race-condition">file system races</a>, and many 
other kinds of errors occur frequently in file system operations, users should be aware 
that any filesystem operational function, no matter how apparently innocuous, may encounter 
an error.&nbsp;See <a href="#Error-reporting">Error reporting</a>. <i>-- end note</i>]</p>
<h4><a name="Function-specifications">Operational function specifications</a></h4>
<pre>path <a name="absolute">absolute</a>(const path&amp; p, const path&amp; base=current_path());</pre>
  <blockquote>
  <p><i>Returns:</i> A <a href="#Absolute-path">absolute path</a> composed according to the 
  following table</p>
  <table border="1" cellpadding="5" cellspacing="0" bordercolor="#111111" style="border-collapse: collapse">
    <tr>
      <td align="center">&nbsp;</td>
      <td align="center"><b><code>p.has_root_directory()</code></b></td>
      <td align="center"><b><code>!p.has_root_directory()</code></b></td>
    </tr>
    <tr>
      <td align="center"><b><code>p.has_root_name()</code></b></td>
      <td align="center"><code>return p</code></td>
      <td align="center"><code>return p.root_name() / 
      absolute(base).root_directory()<br>
      / absolute(base).relative_path() / p.relative_path()</code></td>
    </tr>
    <tr>
      <td align="center"><b><code>!p.has_root_name()</code></b></td>
      <td align="center"><code>return absolute(base).root_name()<br>
      / p</code></td>
      <td align="center"><code>return absolute(base) / p</code></td>
    </tr>
  </table>
  <p dir="ltr">[<i>Note:</i> For the returned path, <code>rp,</code> <code>
  rp.is_absolute()</code> is true. <i>-- end note</i>]</p>
  <p><i>Throws:</i> If <code>base.is_absolute()</code> is true, throws only if 
  memory allocation fails.</p>
</blockquote>
<pre>path <a name="canonical">canonical</a>(const path&amp; p, const path&amp; base = current_path());
path canonical(const path&amp; p, system::error_code&amp; ec);
path canonical(const path&amp; p, const path&amp; base, system::error_code&amp; ec);</pre>
<blockquote>
<p><i>Overview:</i> Converts <code>p</code>, which must exist, to an absolute 
path that has no symbolic link, <a href="#Dot">dot</a>, 
or <a href="#Dot">dot-dot</a> elements. </p>
<p><i>Returns:</i> A <a href="#Canonical-path">canonical path</a> that refers to 
the same file system object as <code>absolute(p,base)</code>. For the overload 
without a <code>base</code> argument, <code>base</code> is <code>current_path()</code>.</p>
  <p><i>Throws:</i>&nbsp; As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  
  <p><i>Remarks:</i> <code>!exists(p)</code> is an error.</p>
  
  <p>[<i>Note:</i> Canonical pathnames allow security checking of a path (eg. 
  does this path live in /home/goodguy or /home/badguy?)&nbsp; -- end note]</p>
  
</blockquote>
<pre>void <a name="copy">copy</a>(const path&amp; from, const path&amp; to);
void copy(const path&amp; from, const path&amp; to, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i> As if</p>
  
  <blockquote>
    <pre>file_status s(symlink_status(from<i>[</i><code>, ec</code><i>]</i>));
if(is_symlink(s))
  copy_symlink(from, to<i>[</i><code>, ec</code><i>]</i>);
else if(is_directory(s))
  copy_directory(from, to<i>[</i><code>, ec</code><i>]</i>);
else if(is_regular_file(s))
  copy_file(from, to, copy_option::fail_if_exists<i>[</i><code>, ec</code><i>]</i>);
else
<i> Report error as specified in <a href="#Error-reporting">Error reporting</a>.</i></pre>
  </blockquote>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  
</blockquote>
<pre>void <a name="copy_directory">copy_directory</a>(const path&amp; from, const path&amp; to);
void copy_directory(const path&amp; from, const path&amp; to, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects: </i></p>
  
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  
</blockquote>
<pre>void copy_file(const path&amp; from, const path&amp; to);
void copy_file(const path&amp; from, const path&amp; to, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects: </i><code>copy_file(from, to, 
  copy_option::fail_if_exists</code><i>[</i><code>, ec</code><i>]</i><code>)</code>.</p>
  
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  
</blockquote>
<pre>void <a name="copy_file">copy_file</a>(const path&amp; from, const path&amp; to, <a href="#copy_option">copy_option</a> option);
void <a name="copy_file2">copy_file</a>(const path&amp; from, const path&amp; to, <a href="#copy_option">copy_option</a> option, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i> If <code>option == copy_option::</code><code>fail_if_exists 
  &amp;&amp; exists(to)</code>, an error is reported. Otherwise, the contents and attributes of the file <code>from</code> 
  resolves to are copied to the file <code>to</code> resolves to.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre>void <a name="copy_symlink">copy_symlink</a>(const path&amp; existing_symlink, const path&amp; new_symlink);
void copy_symlink(const path&amp; existing_symlink, const path&amp; new_symlink, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects: </i><code>create_symlink(read_symlink(existing_symlink</code><i>[</i><code>, ec</code><i>]</i><code>), 
  new_symlink</code><i>[</i><code>, ec</code><i>]</i><code>)</code>.</p>
  
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  
</blockquote>
<pre>bool <a name="create_directories">create_directories</a>(const path&amp; p);
bool <a name="create_directories2">create_directories</a>(const path&amp; p, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Requires:</i> <code>p.empty() || <br>
  forall px: px == p || is_parent(px, p): is_directory(px) || !exists( px )</code>
  </p>
  <p><i>Postcondition:</i> <code>is_directory(p)</code></p>
  <p><i>Returns:</i> The value of <code>!exists(p)</code> prior to the 
  establishment of the postcondition.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre>bool <a name="create_directory">create_directory</a>(const path&amp; p);
bool <a name="create_directory2">create_directory</a>(const path&amp; p, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i> Attempts to create the directory <code>p</code> resolves to, 
  as if by<i> POSIX </i><code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/mkdir.html">mkdir()</a></code> with a second argument of S_IRWXU|S_IRWXG|S_IRWXO. </p>
  <p><i>Postcondition:</i> <code>is_directory(p)</code></p>
  <p><i>Returns:</i> <code>true</code> if a new directory was created, otherwise 
  <code>false</code>.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre>void <a name="create_directory_symlink">create_directory_symlink</a>(const path&amp; to, const path&amp; new_symlink);
void create_directory_symlink(const path&amp; to, const path&amp; new_symlink, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i> 
  Establishes the postcondition, as if by <i>
  POSIX</i>
  <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/symlink.html">
  symlink()</a></code>.</p>
  <p><i>
  Postcondition:</i> <code>new_symlink</code> resolves to a symbolic link file that 
  contains an unspecified representation of <code>to</code>.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  <p dir="ltr">[<i>Note:</i> 
  Some operating systems, such as Windows, require symlink creation to 
  identify that the link is to a directory. Portable code should use <code>
  create_directory_symlink()</code> to create directory symlinks rather than
  <code>create_symlink()</code>  <i>-- end note</i>]</p>
  <p>[<i>Note:</i> 
  Some operating systems do not support symbolic links at all or support 
  them only for regular files. 
  Some file systems do not 
  support 
  symbolic links regardless of the operating system - the FAT file system used on 
  memory cards and flash drives, for example.  <i>-- end note</i>]</p>
  </blockquote>
<pre>void <a name="create_hard_link">create_hard_link</a>(const path&amp; to, const path&amp; new_hard_link);
void <a name="create_hard_link2">create_hard_link</a>(const path&amp; to, const path&amp; new_hard_link, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i> Establishes the postcondition, as if by
   <i>POSIX</i>
   <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/link.html">
  link()</a></code>.</p>
  <p><i>Postcondition:</i></p>
  <ul>
    <li>&nbsp;<code>exists(to) &amp;&amp; 
    exists(</code><code>new_hard_link</code><code>) &amp;&amp; equivalent(to, 
     
    </code><code>new_hard_link</code><code>)</code></li>
    <li>The contents of the file or directory
    <code>to</code> resolves to are unchanged.</li>
  </ul>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  <p>[<i>Note:</i> 
  Some operating systems do not support hard links at all or support 
  them only for regular files. Some file systems do not support hard 
  links regardless of the operating system - the FAT file system used on memory 
  cards and flash drives, for example. Some file systems limit the number of 
  links per file.  <i>-- end note</i>]</p>
  </blockquote>
<pre>void <a name="create_symlink">create_symlink</a>(const path&amp; to, const path&amp; new_symlink);
void <a name="create_symlink2">create_symlink</a>(const path&amp; to, const path&amp; new_symlink, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i> 
  Establishes the postcondition, as if by <i>
  POSIX</i>
  <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/symlink.html">
  symlink()</a></code>.</p>
  <p><i>
  Postcondition:</i> <code>new_symlink</code> resolves to a symbolic link file that 
  contains an unspecified representation of <code>to</code>.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  <p>[<i>Note:</i> 
  Some operating systems do not support symbolic links at all or support 
  them only for regular files. 
  Some file systems do not 
  support 
  symbolic links regardless of the operating system - the FAT system used on 
  memory cards and flash drives, for example.  <i>-- end note</i>]</p>
  </blockquote>
<pre>path <a name="current_path">current_path</a>();
path <a name="current_path2">current_path</a>(system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Returns:</i> The current working directory path, as if by <i>POSIX</i>
  <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/getcwd.html">
  getcwd()</a></code>. <code>is_absolute()</code> is true for the returned path.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  <p>[<i>Note: </i>The <code>
  current_path()</code> name was chosen to emphasize that the return is a 
  path, not just a single directory name.</p>
  <p>The current path as returned by many operating systems is a dangerous 
  global variable. It may be changed unexpectedly by a third-party or system 
  library functions, or by another thread.&nbsp; <i>-- end note</i>]</p>
</blockquote>
<pre>void current_path(const path&amp; p);
void current_path(const path&amp; p, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i> 
  Establishes the postcondition, as if by <i>
  POSIX</i>
  <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/chdir.html">
  chdir()</a></code>.</p>
<p><i>Postcondition:</i> <code>equivalent(p, current_path())</code>.</p>
<p><i>Throws:</i> As specified in
<a href="#Error-reporting">
Error reporting</a>.</p>
  <p>[<i>Note: </i>The current path for many operating systems is a dangerous 
  global state. It may be changed unexpectedly by a third-party or system 
  library functions, or by another thread.&nbsp; <i>-- end note</i>]</p>
</blockquote>
<pre>bool <a name="exists">exists</a>(file_status s) noexcept;</pre>
<blockquote>
  <p><i>Returns:</i>
  <code>status_known(s) &amp;&amp; s.type() != file_not_found</code></p>
</blockquote>
<pre>bool <a name="exists2">exists</a>(const path&amp; p);
bool <a name="exists3">exists</a>(const path&amp; p, system::error_code&amp; ec) noexcept;</pre>
<blockquote>
  <p><i>Returns:</i> <code>exists(status(p))</code> or <code>exists(status(p, ec))</code>, 
  respectively.</p>
<p><i>Throws:</i> <code>filesystem_error</code>; overload with <code>error_code&amp;</code> throws 
nothing.</p>
</blockquote>
<pre><code>bool <a name="equivalent">equivalent</a>(const path&amp; p1, const path&amp; p2);
bool <a name="equivalent2">equivalent</a>(const path&amp; p1, const path&amp; p2, system::error_code&amp; ec);</code></pre>
<blockquote>
  <p><i>Effects:</i> Determines <code>file_status s1</code> 
  and <code>s2</code>, as if by <code>status(p1)</code> and&nbsp; <code>status(p2)</code>, 
  respectively.</p>
  <p><i>Returns:</i> <code>true</code>, if <code>sf1 == 
  sf2</code> and <code>p1</code> and <code>p2</code> resolve to the same file 
  system entity, else <code>false</code>.</p>
  <blockquote>
  <p>Two paths are considered to resolve to the same 
  file system entity if two candidate entities reside on the same device at the 
  same location. This is determined as if by the values of the <i>POSIX</i>
  <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">
  stat</a></code> structure<code>,</code> obtained as if by <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/stat.html">
  stat()</a></code> for the two paths, having equal <code>st_dev</code> values 
  and equal <code>st_ino</code> values.</p>
  <p>[<i>Note:</i> <i>POSIX</i> requires that <i>&quot;st_dev</i> 
  must be unique within a Local Area Network&quot;. Conservative <i>POSIX</i> 
  implementations may also wish to check for equal <code>st_size</code> and
  <code>st_mtime</code> values. <i>Windows</i> implementations may use <code>
  GetFileInformationByHandle()</code> as a surrogate for <code>stat()</code>, 
  and consider &quot;same&quot; to be equal values for <code>dwVolumeSerialNumber</code>,
  <code>nFileIndexHigh</code>, <code>nFileIndexLow</code>, <code>nFileSizeHigh</code>,
  <code>nFileSizeLow</code>, <code>ftLastWriteTime.dwLowDateTime</code>, and
  <code>ftLastWriteTime.dwHighDateTime</code>. <i>-- end note</i>]</p>
  </blockquote>
  <p><i>Throws:</i> <code>filesystem_error</code>
  if <code>(!exists(s1) &amp;&amp; !exists(s2)) || (is_other(s1) &amp;&amp; is_other(s2))</code>, 
  otherwise as specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<div dir="ltr">
<pre>uintmax_t <a name="file_size">file_size</a>(const path&amp; p);
uintmax_t <a name="file_size2">file_size</a>(const path&amp; p, system::error_code&amp; ec);</pre>
</div>
<blockquote>
  <p><i>Returns:</i> If <code>exists(p) &amp;&amp; is_regular_file(p)</code>, the size 
  in bytes 
  of the file <code>p</code> resolves to, determined as if by the value of 
  the <i>POSIX</i> <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">stat</a></code> structure member <code>st_size</code> 
  obtained as if by <i>POSIX</i> <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/stat.html">stat()</a></code>. 
  Otherwise, <code>static_cast&lt;uintmax_t&gt;(-1)</code>.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre>uintmax_t <a name="hard_link_count">hard_link_count</a>(const path&amp; p);
uintmax_t hard_link_count(const path&amp; p, system::error_code&amp; ec);</pre>
<blockquote>

  <p><i>Returns:</i> The number of hard links for <code>p</code>.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>

</blockquote>

<pre>const path&amp; <a name="initial_path">initial_path</a>();
const path&amp; <a name="initial_path">initial_path</a>(<code>system::error_code&amp; ec</code>);</pre>
<blockquote>
  <p><i>Returns:</i> 
  <code>current_path()</code> as of the first call to <code>initial_path()</code>.</p>
  <p>[<i>Note:</i> <code>
  initial_path()</code> is not thread safe, and may return an undesirable result 
  if called subsequent to a change to the current directory. These problems can 
  be avoided by calling <code>initial_path()</code> immediately on entry to 
  main().&nbsp; <i>--end note</i>]</p>
  <p><i>Throws:</i> For the first call, as specified in
  <a href="#Error-reporting">
  Error reporting</a>. Subsequent calls throw nothing.</p>
</blockquote>
<pre>bool <code><a name="is_directory">is_directory</a></code>(file_status s) noexcept;</pre>
<blockquote>
  <p><i>Returns:</i> 
  <code>s.type() == directory_file</code></p>
</blockquote>
<pre><code>bool <a name="is_directory2">is_directory</a>(const path&amp; p);
bool <a name="is_directory3">is_directory</a>(const path&amp; p, system::error_code&amp; ec) noexcept;</code></pre>
<blockquote>
  <p dir="ltr"><i>Returns:</i> <code>is_directory(status(p))</code> or <code>is_directory(status(p, ec))</code>, 
  respectively.</p>
<p><i>Throws:</i> <code>filesystem_error</code>; overload with <code>error_code&amp;</code> throws 
nothing.</p>
</blockquote>
<pre><code>bool <a name="is_empty">is_empty</a>(const path&amp; p);
bool <a name="is_empty2">is_empty</a></a>(const path&amp; p, system::error_code&amp; ec);</code></pre>
<blockquote>
  <p><i>Effects:</i> Determines <code>file_status s</code>, as if by <code>
  status(p, ec)</code>.</p>
  <p><i>Returns:</i> <code>is_directory(s)<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ? 
  directory_iterator(p) == directory_iterator()<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; : file_size(p) == 0;</code></p>
</blockquote>
<pre>bool <code><a name="is_regular_file">is_regular_file</a></code>(file_status s) noexcept;</pre>
<blockquote>
  <p><i>Returns:</i>
  <code>s.type() == regular_file</code></p>
</blockquote>
<pre><code>bool <a name="is_regular_file2">is_regular_file</a>(const path&amp; p);</code></pre>
<blockquote>
  <p><i>Returns:</i> <code>is_regular_file(status(p))</code>.</p>
  <p><i>Throws:</i> <code>filesystem_error</code> 
  if <code>status(p)</code> would throw <code>filesystem_error.</code></p>
  </blockquote>
<pre><code>bool <a name="is_regular_file3">is_regular_file</a>(const path&amp; p, system::error_code&amp; ec) noexcept;</code></pre>
<blockquote>
  <p><i>Effects:</i> Sets <code>ec</code> as if by <code>status(p, ec)</code>. [<i>Note:</i>
      <code>status_error</code>,
      <code>file_not_found</code> 
  and
      <code>type_unknown</code> 
  cases set <code>ec</code> 
  to error values. To distinguish between cases, call the <code>
  status</code> 
  function directly. <i>-- end 
  note</i>] </p>
  <p><i>Returns:</i> <code>is_regular_file(status(p, ec))</code>.</p>
</blockquote>
<pre>bool <a name="is_other">is_other</a>(file_status s) noexcept;</pre>
<blockquote>
  <p><i>Returns:</i>
  <code>return exists(s) &amp;&amp; !is_regular_file(s) &amp;&amp; !is_directory(s) &amp;&amp; !is_symlink(s)</code></p>
</blockquote>
<pre><code>bool <a name="is_other2">is_other</a>(const path&amp; p);
bool <a name="is_other3">is_other</a>(const path&amp; p, system::error_code&amp; ec) noexcept;</code></pre>
<blockquote>
  <p><i>Returns:</i> <code>is_other(status(p))</code> or <code>is_other(status(p, ec))</code>, 
  respectively.</p>
  <p><i>Throws:</i> <code>filesystem_error</code>; overload with <code>error_code&amp;</code> throws 
  nothing.</p>
</blockquote>
<pre>bool <a name="is_symlink">is_symlink</a>(file_status s) noexcept;</pre>
<blockquote>
  <p><i>Returns:</i> 
  <code>s.type() == symlink_file</code></p>
</blockquote>
<pre><code>bool <a name="is_symlink2">is_symlink</a>(const path&amp; p);
bool <a name="is_symlink3">is_symlink</a>(const path&amp; p, system::error_code&amp; ec) noexcept;</code></pre>
<blockquote>
  <p><i>Returns:</i> <code>is_symlink(symlink_status(p))</code> or <code>is_symlink(symlink_status(p, ec))</code>, 
  respectively.</p>
  <p><i>Throws:</i> <code>filesystem_error</code>; overload with <code>error_code&amp;</code> throws 
  nothing.</p>
</blockquote>
<pre>std::time_t <a name="last_write_time">last_write_time</a>(const path&amp; p);
std::time_t <a name="last_write_time2">last_write_time</a>(const path&amp; p<code>, system::error_code&amp; ec</code>);</pre>
<blockquote>
  <p><i>Returns:</i> The time of last data modification of <code>p</code>, determined as if by the 
  value of the <i>POSIX</i> <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">stat</a></code> structure member <code>st_mtime</code>&nbsp; obtained 
  as if by <i>POSIX</i> <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/stat.html">stat()</a></code>.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre>void <a name="last_write_time3">last_write_time</a>(const path&amp; p, const std::time_t new_time);
void <a name="last_write_time4">last_write_time</a>(const path&amp; p, const std::time_t new_time<code>, system::error_code&amp; ec</code>);</pre>
<blockquote>
  <p><i>Effects:</i> Sets the time of last data modification of the file 
  resolved to by <code>p</code> 
  to <code>new_time</code>, as if by <i>POSIX</i> <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/stat.html">stat()</a></code> 
  followed by <i>POSIX</i>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/utime.html">
  <code>utime()</code></a>.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  <p>[<i>Note:</i> A postcondition of <code>last_write_time(p) == 
  new_time</code> is not specified since it might not hold for file systems 
  with coarse time granularity. <i>-- end note</i>]</p>
</blockquote>
<pre>void <a name="permissions">permissions</a>(const path&amp; p, <a href="#symlink_perms">perms</a> prms);
void permissions(const path&amp; p, <a href="#symlink_perms">perms</a> prms, system::error_code&amp; ec);</pre>
<blockquote>
  <p dir="ltr">
  <i>Requires:</i> <code>!((prms &amp; add_perms) &amp;&amp; (prms &amp; remove_perms))</code>.</p>
  <p dir="ltr"><i>Effects:</i> Applies the effective permissions bits from <code>
  prms</code> to the file <code>p</code> resolves to, as if by <i>POSIX</i>
  <code>
  <a href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/fchmodat.html">
  fchmodat()</a></code>. The effective permission bits are determined as 
  specified by the following table. </p>
  <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111">
    <tr>
      <td><b>bits present in <code>prms</code></b></td>
      <td><b>Effective bits applied</b></td>
    </tr>
    <tr>
      <td>Neither <code>add_perms</code> nor <code>remove_perms</code></td>
      <td><code>prms &amp; perms_mask</code></td>
    </tr>
    <tr>
      <td><code>add_perms</code></td>
      <td>
      <p dir="ltr"><code>status(p).permissions() | (prms &amp; 
      <a href="#perms_mask">perms_mask</a>)</code>
      </td>
    </tr>
    <tr>
      <td><code>remove_perms</code></td>
      <td><code>status(p)</code><code>.permissions() &amp; ~(prms &amp; 
      <a href="#perms_mask">perms_mask</a>)
      </code> </td>
    </tr>
  </table>
  <p>[<i>Note:</i> Conceptually permissions are viewed as bits, but the actual 
  implementation may use some other mechanism. -- <i>end note</i>]</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre>path <a name="read_symlink">read_symlink</a>(const path&amp; p);
path read_symlink(const path&amp; p, system::error_code&amp; ec);</pre>
<blockquote>
  <p dir="ltr"><i>Returns:</i>&nbsp; If <code>p</code> resolves to a symbolic 
  link, a <code>path</code> object containing the contents of that symbolic 
  link. Otherwise an empty <code>path</code> object.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>. [<i>Note:</i> It is an error if <code>p</code> does not 
  resolve to a symbolic link. <i>-- end note</i>]</p>
</blockquote>
<pre>bool <a name="remove">remove</a>(const path&amp; p);
bool <a name="remove2">remove</a>(const path&amp; p, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i>&nbsp; If <code>exists(symlink_status(p,ec))</code>, it is 
  removed 
  as if by<i> POSIX </i><code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/remove.html">remove()</a></code>.</p>
  <blockquote>
  <p>[<i>Note:</i> A symbolic link is itself removed, rather than the file it 
  resolves to being removed. <i>-- end note</i>]</p>
  </blockquote>
  <p><i>Postcondition:</i> <code>!exists(symlink_status(p))</code>.</p>
  <p><i>Returns:</i>&nbsp; <code>false</code> if p did not exist in the first 
  place, otherwise <code>true</code>.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre>uintmax_t <a name="remove_all">remove_all</a>(const path&amp; p);
uintmax_t <a name="remove_all2">remove_all</a>(const path&amp; p, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i>&nbsp; Recursively deletes the contents of p if it exists, 
  then deletes file <code>p</code> itself, 
  as if by<i> POSIX </i><code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/remove.html">remove()</a></code>.</p>
  <blockquote>
  <p>[<i>Note:</i> A symbolic link is itself removed, rather than the file it 
  resolves to being removed. <i>-- end note</i>]</p>
  </blockquote>
  <p><i>Postcondition:</i> <code>!exists(p)</code></p>
  <p><i>Returns:</i> The number of files removed.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre>void <a name="rename">rename</a>(const path&amp; old_p, const path&amp; new_p);
void <a name="rename2">rename</a>(const path&amp; old_p, const path&amp; new_p, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i> Renames <code>old_p</code> to <code>new_p</code>, as if by
  <i>POSIX</i> <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/rename.html">
  rename()</a></code>.</p>
  <blockquote>
  <p>[<i>Note:</i> If <code>old_p</code> and <code>new_p</code> resolve to the 
  same existing file, no action is taken. Otherwise, if <code>new_p</code> resolves to an 
  existing non-directory file, it is removed, while if <code>new_p</code> resolves to an 
  existing directory, it is removed if empty on POSIX but is an error on Windows. A symbolic link is itself renamed, rather than 
  the file it resolves to being renamed. <i>-- end note</i>]</p>
  </blockquote>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre>void <a name="resize_file">resize_file</a>(const path&amp; p, uintmax_t new_size);
void <a name="resize_file2">resize_file</a>(const path&amp; p, uintmax_t new_size, system::error_code&amp; ec);</pre>
<blockquote>
<p><i>Postcondition:</i> <code>file_size() == new_size</code>.</p>
<p><i>Throws:</i> As specified in
<a href="#Error-reporting">
Error reporting</a>.</p>
  <p><i>Remarks:</i> Achieves its postconditions as if by 
  POSIX <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/truncate.html">
  truncate()</a></code>.</p>
</blockquote>
<pre>space_info <a name="space">space</a>(const path&amp; p);
space_info <a name="space2">space</a>(const path&amp; p, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Returns:</i> An object of type <code>
  <a href="#space_info">space_info</a></code>. The value of the <code>space_info</code> object is determined as if by 
  using  <i>POSIX</i> <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/statvfs.html" style="text-decoration: none">
  statvfs()</a></code> to obtain a <i>POSIX</i> struct <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/statvfs.h.html" style="text-decoration: none">
  statvfs</a></code>, and then multiplying its <code>f_blocks</code>, <code>
  f_bfree</code>, and <code>f_bavail</code> members by its <code>f_frsize</code> 
  member, and assigning the results to the <code>capacity</code>, <code>free</code>, 
  and <code>available</code> members respectively. Any members for which the 
  value cannot be determined shall be set to -1.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
</blockquote>
<pre><a href="#file_status">file_status</a> <a name="status">status</a>(const path&amp; p);</pre>
<blockquote>
  <p><i>Effects: </i>As if:</p>
  <blockquote>
    <pre>system::error_code ec;
file_status result = status(p, ec);
if (result == status_error)
  throw filesystem_error(<i>implementation-supplied-message</i>, p, ec);
return result;</pre>
  </blockquote>
  <p><i>Returns:</i> See above.</p>
  <p><i>Throws:</i> <code>filesystem_error</code>. 
[<i>Note:</i> <code>result</code> values of <code>
      file_status(file_not_found)</code>and <code>
      file_status(type_unknown)</code> are not considered failures and do not 
  cause an exception to be 
thrown.<i> -- end note</i>] </p>
  </blockquote>
<pre><a href="#file_status">file_status</a> <a name="status2">status</a>(const path&amp; p, system::error_code&amp; ec) noexcept;</pre>
<blockquote>
  <p><i>Effects: </i></p>
  <blockquote>
    <p>If possible, determines the attributes 
    of the file
    <code>p</code> resolves to, as if by<i> POSIX </i> <code>
  <a href="http://www.opengroup.org/onlinepubs/000095399/functions/stat.html">stat()</a></code>.</p>
      If, during attribute determination, the underlying file system API reports 
    an error, sets <code>ec</code> to indicate the specific error reported. 
    Otherwise, <code>ec.clear()</code>.<blockquote>
      <p>[<i>Note:</i> This allows users to inspect the specifics of underlying 
      API errors even when the value returned by <code>status()</code> is not <code>
      file_status(status_error)</code>.&nbsp; <i>--end note</i>]</p>
    </blockquote>
    </blockquote>
  <p><i>Returns:</i></p>
  <blockquote>
    <p>If <code>ec != error_code()</code>:</p>
    <ul>
      <li>If the specific error indicates that <code>p</code> cannot be resolved 
      because some element of the path does not exist, return <code>
      file_status(file_not_found)</code>. [<i>Note:</i> POSIX errors that 
      indicate this are ENOENT or ENOTDIR. Windows equivalents 
      include ERROR_FILE_NOT_FOUND, ERROR_PATH_NOT_FOUND, ERROR_INVALID_NAME, 
      ERROR_INVALID_PARAMETER, ERROR_BAD_PATHNAME, and ERROR_BAD_NETPATH. <i>-- 
      end note</i>]<br>
&nbsp;</li>
      <li>Otherwise, if the specific error indicates that <code>p</code> can be resolved 
      but the attributes cannot be determined, return <code>
      file_status(type_unknown)</code>. [<i>Note: </i>For example, Windows 
      ERROR_SHARING_VIOLATION errors. For POSIX, the case never arises. <i>-- end 
      note</i>]<br>
&nbsp;</li>
      <li>Otherwise, return <code>
      file_status(status_error)</code>.</li>
    </ul>
        <blockquote>
        <p>[<i>Note:</i> These semantics distinguish between 
        <code>p</code> being known not to exist, 
        <code>p</code> existing but not being able to determine its attributes, 
        and there being an error that prevents even knowing if 
        <code>p</code> exists. These 
        distinctions are important to some use cases.&nbsp;<i>--end note</i>]</p>
    </blockquote>
    <p>Otherwise,</p>
    <ul>
      <li>If the attributes indicate a regular file, as if by <i>POSIX</i>&nbsp;<a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">S_ISREG()</a>, 
      return <code>
      file_status(regular_file)</code>. [<i>Note:</i> <code>
regular_file</code> implies appropriate <code>&lt;fstream&gt;</code> operations 
      would succeed, assuming no hardware, permission, access, or file system 
      race 
      errors. Lack of
<code>regular_file</code> does not necessarily imply <code>&lt;fstream&gt;</code> operations would 
fail on a directory.
<i>-- end note</i>]<br>
&nbsp;</li>
      <li>Otherwise, if the attributes indicate a directory, as if by <i>POSIX</i>
      <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">S_ISDIR()</a>, 
      return <code>
      file_status(directory_file)</code>. [<i>Note:</i> <code>directory_file</code> implies <code>
directory_iterator(p)</code>would succeed.
<i>-- end note</i>]<br>
&nbsp;</li>
      <li>Otherwise, if the attributes indicate a block special file, as if by <i>POSIX</i>
      <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">S_ISBLK()</a>, 
      return <code>
      file_status(block_file)</code>.<br>
&nbsp;</li>
      <li>Otherwise, if the attributes indicate a character special file, as if by <i>POSIX</i>
      <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">S_ISCHR()</a>, 
      return <code>
      file_status(character_file)</code>.<br>
&nbsp;</li>
      <li>Otherwise, if the attributes indicate a fifo or pipe file, as if by <i>POSIX</i>
      <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">S_ISFIFO()</a>, 
      return <code>
      file_status(fifo_file)</code>.<br>
&nbsp;</li>
      <li>Otherwise, if the attributes indicate a socket, as if by <i>POSIX</i>
      <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">S_ISSOCK()</a>, 
      return <code>
      file_status(socket_file)</code>.<br>
&nbsp;</li>
      <li>Otherwise, return <code>
      file_status(type_unknown)</code>.</li>
    </ul>
    </blockquote>
      <p><i>Remarks:</i> If a symbolic link is encountered during pathname 
      resolution, 
      pathname resolution continues using the contents of the symbolic link.</p>
</blockquote>
<pre>bool <a name="status_known">status_known</a>(file_status s) noexcept;</pre>
<blockquote>
  <p><i>Returns:</i>
  <code>s.type() != status_error</code></p>
</blockquote>
<pre>file_status <a name="symlink_status">symlink_status</a>(const path&amp; p);
file_status <a name="symlink_status2">symlink_status</a>(const path&amp; p, system::error_code&amp; ec) noexcept;</pre>
<blockquote>
  <p><i>Effects:</i>&nbsp; Same as <a href="#status">status()</a>, above, 
  except that the attributes 
    of
    <code>p</code> are determined as if by<i> POSIX </i> <code>
    <a href="http://www.opengroup.org/onlinepubs/000095399/functions/lstat.html">
    lstat()</a></code>.</p>
</blockquote>
<blockquote>
      <p><i>Returns:</i> Same as <a href="#status">status()</a>, above, except 
      that if the attributes indicate a symbolic link, as if by <i>POSIX</i>
      <a class="external" href="http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html">
      S_ISLNK()</a>, return <code>file_status(symlink_file)</code>.</p>
      <p><i>Remarks:</i> Pathname resolution terminates if <code>p</code> names a symbolic link.</p>
  <p><i>Throws:</i> <code>filesystem_error</code>; overload with <code>error_code&amp;</code> throws 
  nothing.</p>
</blockquote>
<pre>path <a name="system_complete">system_complete</a>(const path&amp; p);
path <a name="system_complete2">system_complete</a>(const path&amp; p, system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Effects:</i> Composes an absolute path from <code>p</code>, using the 
  same rules used by the operating system to resolve a path passed as the 
  filename argument to standard library open functions.</p>
  <p><i>Returns:</i> The composed path.</p>
  <p><i>Postcondition:</i> For the returned path, <code>rp,</code> <code>
  rp.is_absolute()</code> is true.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  <p>[<i>Note:</i> For <i>POSIX</i>, <code>system_complete(p)</code> has the same semantics as
  <code>complete(p, current_path())</code>.</p>
  <p><a name="windows_effects">For <i>Windows</i></a>, <code>system_complete(p)</code> has the 
  same semantics as <code>complete(ph, current_path())</code> if 
  <code>p.is_absolute() || !p.has_root_name()</code> or <code>p</code> and <code>base</code> have the same
  <code>root_name()</code>. 
  Otherwise it acts like <code>complete(p, kinky)</code>, where <code>kinky</code> 
  is the current directory for the <code>p.root_name()</code> drive. This will 
  be the current directory of that drive the last time it was set, and thus may 
  be <b>residue left over from a prior program</b> run by the command 
  processor! Although these semantics are often useful, they are also very 
  error-prone.</p>
  <p>See <a href="#complete_note">
  <i>complete()</i> note</a> for usage suggestions. <i>-- end note</i>]</p>
</blockquote>
<pre>path <a name="temp_directory_path">temp_directory_path</a>();
path temp_directory_path(system::error_code&amp; ec);</pre>
<blockquote>
  <p><i>Returns:</i> A directory path suitable for temporary files under the 
  conventions of the operating system. The specifics of how this path is 
  determined are implementation defined. An error shall be reported if<code> !exists(p) 
  || !is_directory(p)</code>, where <code>p</code> is the path to be returned.</p>
  <p><i>POSIX:</i> The path supplied by the first environment variable found in the 
  list TMPDIR, TMP, TEMP, TEMPDIR. If none of these are found, <code>&quot;/tmp&quot;</code>.</p>
  <p><i>Windows:</i> The path reported by the <i>Windows</i> <code>GetTempPath</code> API function.</p>
  <p><i>Throws:</i> As specified in <a href="#Error-reporting">
  Error reporting</a>.</p>
  <p>[<i>Note: </i>The <code>temp_directory_path()</code> name was chosen to emphasize that the return is a 
  path, not just a single directory name.&nbsp; <i>-- end note</i>]</p>
</blockquote>
<pre>path <a name="unique_path">unique_path</a>(const path&amp; model=&quot;%%%%-%%%%-%%%%-%%%%&quot;);
path unique_path(const path&amp; model, system::error_code&amp; ec);</pre>
<blockquote>
  <p>The <code>unique_path</code> function generates a path name suitable for 
  creating temporary files, including directories. The name is based 
  on a model that uses the percent sign character to specify replacement by a 
  random hexadecimal digit. [<i>Note:</i> The more bits of randomness in the 
  generated path name, the less likelihood of prior existence or being guessed. 
  Each replacement hexadecimal digit in the model adds four bits of randomness. 
  The default model thus provides 64 bits of randomness. This is sufficient for 
  most applications. <i>--end note</i>]</p>
  <p><i>Returns:</i> A path identical to <code>model</code>, except that each 
  occurrence of a percent sign character is replaced by a random hexadecimal 
  digit character in the range 0-9, a-f.</p>
  <p><i>Throws:</i> As specified in
  <a href="#Error-reporting">
  Error reporting</a>.</p>
  <p><i>Remarks:</i> Implementations are encouraged to obtain the required 
  randomness via a
  <a href="http://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator">
  cryptographically secure pseudo-random number generator</a>, such as one 
  provided by the operating system. [<i>Note</i>: Such generators may block 
  until sufficient entropy develops. <i>--end note</i>]</p>
</blockquote>

<p><span style="font-style: italic; background-color: #E0E0E0">End of new 
Clause.</span></p>
<p dir="ltr"><span style="font-style: italic; background-color: #E0E0E0">Modify <a name="File-streams">File streams</a> 
[fstreams] as follows:</span></p>
<p><span style="font-style: italic; background-color: #E0E0E0">To class 
basic_filebuf public members add:</span></p>
<blockquote>
<pre>basic_filebuf&lt;charT,traits&gt;* open(const path&amp; p, std::ios_base::openmode mode);</pre>

</blockquote>
<p><span style="font-style: italic; background-color: #E0E0E0">To class 
basic_ifstream public members add:</span></p>

<blockquote>
<pre>explicit basic_ifstream(const path&amp; p, std::ios_base::openmode mode=std::ios_base::in)</pre>

<pre>void open(const path&amp; p, std::ios_base::openmode mode=std::ios_base::in);</pre>

</blockquote>
<p><span style="font-style: italic; background-color: #E0E0E0">To class 
basic_ofstream public members add:</span></p>

<blockquote>
  <pre>explicit basic_ofstream(const path&amp; p, std::ios_base::openmode mode=std::ios_base::out);</pre>
  <pre>void open(const path&amp; p, std::ios_base::openmode mode=std::ios_base::out);</pre>
</blockquote>
<p><span style="font-style: italic; background-color: #E0E0E0">To class 
basic_fstream public members add:</span></p>
<blockquote>
  <pre>explicit basic_fstream(const path&amp; p,
  std::ios_base::openmode mode=std::ios_base::in | std::ios_base::out);</pre>
  <pre>void open(const path&amp; p,
  std::ios_base::openmode mode=std::ios_base::in | std::ios_base::out);</pre>
</blockquote>
<p>

<span style="font-style: italic; background-color: rgb(224, 224, 224);">
End of proposed wording.</span> </p>
<hr>
<h2><a name="Issues-List">Issues List</a></h2>
<hr>
<h3>Issue 1: What is the appropriate namespace?&nbsp;&nbsp;&nbsp; Status: 
Tentatively resolved</h3>
<h4>Discussion</h4>
<p>The N3335 proposal places the library in namespace <code>std::tr2::files</code>. 
Rationale for a sub-namespace is that the library uses several names that don't 
seem appropriate for namespace <code>tr2</code> since full standardization would 
then put the names into <code>std</code>. The function names <code>remove</code> 
and <code>rename</code> are of particular concern because these functions differ 
in behavior from current standard library functions with those names. It also 
doesn't seem desirable to preempt names like <code>equivalent</code> and <code>
status</code>.</p>
<h4>Resolution</h4>
<p><i>Kona: Strong support for <code>filesystem</code> as the library's 
namespace. Strong support for a technical report namespace that alerts uses that 
contents are likely to change if and when they later get moved into the 
standard. </i></p>
<p><i>No decision yet on a TR namespace; <code>experimental</code> being used as 
a placeholder. Thus the full namespace is changed to <code>
std::experimental::filesystem.</code></i></p>
<hr>
<h3>Issue 2: Excessive use of <code>const codecvt_type&amp;</code> arguments&nbsp;&nbsp;&nbsp; 
Status: Open</h3>
<h4>Discussion</h4>
<p>Users sometimes need to do path conversions that use something other than the 
imbued codecvt facet. The need is particularly acute in multi-threaded 
applications where changing the imbued facet would introduce a data race. That 
said, providing an optional <code>const codecvt_type&amp;</code> argument for every 
function where the need might possibly arise is excessive because its use is so 
rare and it adds considerable interface clutter.</p>
<h4>Proposed resolution</h4>
<p dir="ltr"><i>Kona:</i></p>
<p dir="ltr"><i>Remove all existing class path <code>const codecvt_type&amp;</code> 
arguments.</i></p>
<p dir="ltr"><i>Beman to pursue separate encoding conversion functionality, per 
Thursday N3336 &quot;Adapting standard library strings and IO to a Unicode World&quot; 
discussion. See Kona wiki.</i></p>
<p dir="ltr"><i>If a separate encoding conversion facility isn't possible, then 
some form of minimal class path encoding conversion facility will be needed. 
But..., the LWG would like to see use cases and clearer explanation of 
motivation before deciding on specifics, and be very sure that there is no way 
to achieve with existing std library functionality, albeit with some loss of 
efficiency.</i></p>
<hr>
<h3>Issue 3: Possible &quot;implicit cast to native type&quot;?&nbsp;&nbsp;&nbsp;&nbsp; 
Status: Open</h3>
<h4>Discussion</h4>
<p>In Bloomington there was discussion of &quot;implicit cast to implicit cast to 
native OS type to inter operate with existing iostream library and native 
functions instead of modifying fstream&quot;.</p>
<h4>Proposed resolution</h4>
<p><i>Kona: The Dinkumware/Microsoft implementation has added an implicit 
conversion to the string type, eliminating any need to modify fstream. 
(Discussion: might be safer to make the implicit conversion protected, then make 
fstream classes friends).</i></p>
<p><i>Action: Beman to investigate, test, as avoiding modification of existing 
header and classes is much desired.</i></p>
<hr>
<h3>Issue 4: Given move semantics, it is best not to return const strings.&nbsp;&nbsp;&nbsp;&nbsp; 
Status: Resolved</h3>
<h4>Discussion</h4>
<p>The issue title pretty much says it all.</p>
<h4>Proposed resolution</h4>
<p><i>Kona: Return plain strings. Remove the permission for implementations to 
return const refs, since uses are not in performace critical code and subtle 
portability bugs may occur.</i></p>
<p><i>Action: Beman to apply to proposed wording.</i></p>
<hr>
<h3>Issue 5: Is there a way to handle characters that are illegal for particular 
OS?&nbsp;&nbsp;&nbsp;&nbsp; Status: NAD</h3>
<h4>Discussion</h4>
<p>Question raised by Pablo in Bloomington.</p>
<h4>Proposed resolution</h4>
<p>Beman suggests NAD, Future. I've done some work on this, including looking at 
systems like OpenVMS that have an escape mechanism to handle otherwise 
unrepresentable characters. There was a comment to that effect in N3239. I 
believe it should be deferred to some future release since (1) it is complex 
enough that I'd like to see actual implementation and use experience (presumably 
via Boost), and (2) I can't recall a user ever requesting such a feature.</p>
<p><i>Kona: No consensus for change, since there doesn't appear to be any 
compelling use case.</i></p>
<hr>
<h3>Issue 6: Could allocator support be added to class path?&nbsp;&nbsp;&nbsp;&nbsp; 
Status: Open</h3>
<h4>Discussion</h4>
<p>Question raised by a committee member in private email.</p>
<p><i>Kona: Much discussion.</i></p>
<p><i>Action: Alisdair to write paper, based on a real implementation, so that 
it is possible to assess the impact on interface, performance, etc.</i></p>
<p><i>Post-Kona: Alisdair will defer paper until after TR. </i></p>
<hr>
<h3>Issue 7: How should class path inserter and extractor be specified?&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
Status: Resolved</h3>
<h4>Discussion</h4>
<p>Class <code>path</code> currently is specified to used the Boost detail <code>
quoted</code> stream manipulator. A path object is inserted delimited by quotes, 
and extracted accordingly, ensuring that paths containing spaces are 
round-tripped correctly.&nbsp; Quotes in the path itself are escaped, and io 
state is saved and restored.</p>
<p>See
<a href="http://www.boost.org/doc/libs/1_48_0/libs/io/doc/quoted_manip.html">
http://www.boost.org/doc/libs/1_48_0/libs/io/doc/quoted_manip.html</a></p>
<p>Since the standard can't specify behavior in terms of something in Boost, we 
have to change the specification. Since the <code>quoted</code> stream 
manipulator is a handy little component, the issue is raised as to whether it 
should go in TR2.</p>
<h4>Resolution</h4>
<p><i>Kona: Specify the path inserter and extractor to have the desired 
behavior without reference to how it is achieved. (If someone wants to propose a 
quoted manipulator, that's a separate proposal for a different TR.)</i></p>
<p><i>Action:&nbsp; Beman to apply to proposed wording.</i></p>
<hr>
<p>

<h2><a name="Path-decomposition-table">Path decomposition table</a></h2>
<p>The table is generated by a program compiled with the Boost implementation.</p>
<p>Shaded entries indicate cases where <i>POSIX</i> and <i>Windows</i> 
implementations yield different results. The top value is the
<i>POSIX</i> result and the bottom value is the <i>Windows</i> result. <br>
<table border="1" cellspacing="0" cellpadding="5">
<p>
<tr><td><b>Constructor<br>argument</b></td>
<td><b>Iteration<br>over<br>Elements</b></td>
<td><b><code>string()</code></b></td>
<td><b><code>generic_<br>string()</code></b></td>
<td><b><code>root_<br>path()</code></b></td>
<td><b><code>root_<br>name()</code></b></td>
<td><b><code>root_<br>directory()</code></b></td>
<td><b><code>relative_<br>path()</code></b></td>
<td><b><code>parent_<br>path()</code></b></td>
<td><b><code>filename()</code></b></td>
</tr>
<tr>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
</tr>
<tr>
<td><code>.</code></td>
<td><code>.</code></td>
<td><code>.</code></td>
<td><code>.</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>.</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>..</code></td>
<td><code>..</code></td>
<td><code>..</code></td>
<td><code>..</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>..</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>..</code></td>
</tr>
<tr>
<td><code>foo</code></td>
<td><code>foo</code></td>
<td><code>foo</code></td>
<td><code>foo</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo</code></td>
</tr>
<tr>
<td><code>/</code></td>
<td><code>/</code></td>
<td><code>/</code></td>
<td><code>/</code></td>
<td><code>/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>/</code></td>
</tr>
<tr>
<td><code>/foo</code></td>
<td><code>/,foo</code></td>
<td><code>/foo</code></td>
<td><code>/foo</code></td>
<td><code>/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>/</code></td>
<td><code>foo</code></td>
<td><code>/</code></td>
<td><code>foo</code></td>
</tr>
<tr>
<td><code>foo/</code></td>
<td><code>foo,.</code></td>
<td><code>foo/</code></td>
<td><code>foo/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo/</code></td>
<td><code>foo</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>/foo/</code></td>
<td><code>/,foo,.</code></td>
<td><code>/foo/</code></td>
<td><code>/foo/</code></td>
<td><code>/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>/</code></td>
<td><code>foo/</code></td>
<td><code>/foo</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>foo/bar</code></td>
<td><code>foo,bar</code></td>
<td><code>foo/bar</code></td>
<td><code>foo/bar</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo/bar</code></td>
<td><code>foo</code></td>
<td><code>bar</code></td>
</tr>
<tr>
<td><code>/foo/bar</code></td>
<td><code>/,foo,bar</code></td>
<td><code>/foo/bar</code></td>
<td><code>/foo/bar</code></td>
<td><code>/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>/</code></td>
<td><code>foo/bar</code></td>
<td><code>/foo</code></td>
<td><code>bar</code></td>
</tr>
<tr>
<td><code>//net</code></td>
<td><code>//net</code></td>
<td><code>//net</code></td>
<td><code>//net</code></td>
<td><code>//net</code></td>
<td><code>//net</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>//net</code></td>
</tr>
<tr>
<td><code>//net/foo</code></td>
<td><code>//net,/,foo</code></td>
<td><code>//net/foo</code></td>
<td><code>//net/foo</code></td>
<td><code>//net/</code></td>
<td><code>//net</code></td>
<td><code>/</code></td>
<td><code>foo</code></td>
<td><code>//net/</code></td>
<td><code>foo</code></td>
</tr>
<tr>
<td><code>///foo///</code></td>
<td><code>/,foo,.</code></td>
<td><code>///foo///</code></td>
<td><code>///foo///</code></td>
<td><code>/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>/</code></td>
<td><code>foo///</code></td>
<td><code>///foo</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>///foo///bar</code></td>
<td><code>/,foo,bar</code></td>
<td><code>///foo///bar</code></td>
<td><code>///foo///bar</code></td>
<td><code>/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>/</code></td>
<td><code>foo///bar</code></td>
<td><code>///foo</code></td>
<td><code>bar</code></td>
</tr>
<tr>
<td><code>/.</code></td>
<td><code>/,.</code></td>
<td><code>/.</code></td>
<td><code>/.</code></td>
<td><code>/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>/</code></td>
<td><code>.</code></td>
<td><code>/</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>./</code></td>
<td><code>.,.</code></td>
<td><code>./</code></td>
<td><code>./</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>./</code></td>
<td><code>.</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>/..</code></td>
<td><code>/,..</code></td>
<td><code>/..</code></td>
<td><code>/..</code></td>
<td><code>/</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>/</code></td>
<td><code>..</code></td>
<td><code>/</code></td>
<td><code>..</code></td>
</tr>
<tr>
<td><code>../</code></td>
<td><code>..,.</code></td>
<td><code>../</code></td>
<td><code>../</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>../</code></td>
<td><code>..</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>foo/.</code></td>
<td><code>foo,.</code></td>
<td><code>foo/.</code></td>
<td><code>foo/.</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo/.</code></td>
<td><code>foo</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>foo/..</code></td>
<td><code>foo,..</code></td>
<td><code>foo/..</code></td>
<td><code>foo/..</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo/..</code></td>
<td><code>foo</code></td>
<td><code>..</code></td>
</tr>
<tr>
<td><code>foo/./</code></td>
<td><code>foo,.,.</code></td>
<td><code>foo/./</code></td>
<td><code>foo/./</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo/./</code></td>
<td><code>foo/.</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>foo/./bar</code></td>
<td><code>foo,.,bar</code></td>
<td><code>foo/./bar</code></td>
<td><code>foo/./bar</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo/./bar</code></td>
<td><code>foo/.</code></td>
<td><code>bar</code></td>
</tr>
<tr>
<td><code>foo/..</code></td>
<td><code>foo,..</code></td>
<td><code>foo/..</code></td>
<td><code>foo/..</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo/..</code></td>
<td><code>foo</code></td>
<td><code>..</code></td>
</tr>
<tr>
<td><code>foo/../</code></td>
<td><code>foo,..,.</code></td>
<td><code>foo/../</code></td>
<td><code>foo/../</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo/../</code></td>
<td><code>foo/..</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>foo/../bar</code></td>
<td><code>foo,..,bar</code></td>
<td><code>foo/../bar</code></td>
<td><code>foo/../bar</code></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>foo/../bar</code></td>
<td><code>foo/..</code></td>
<td><code>bar</code></td>
</tr>
<tr>
<td><code>c:</code></td>
<td><code>c:</code></td>
<td><code>c:</code></td>
<td><code>c:</code></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><font size="-1"><i>empty</i></font></td>
<td><span style="background-color: #CCFFCC"><code>c:</code><br><font size="-1"><i>empty</i></font></span></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>c:</code></td>
</tr>
<tr>
<td><code>c:/</code></td>
<td><span style="background-color: #CCFFCC"><code>c:,.</code><br><code>c:,/</code></span></td>
<td><code>c:/</code></td>
<td><code>c:/</code></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:/</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>/</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:/</code><br><font size="-1"><i>empty</i></font></span></td>
<td><code>c:</code></td>
<td><span style="background-color: #CCFFCC"><code>.</code><br><code>/</code></span></td>
</tr>
<tr>
<td><code>c:foo</code></td>
<td><span style="background-color: #CCFFCC"><code>c:foo</code><br><code>c:,foo</code></span></td>
<td><code>c:foo</code></td>
<td><code>c:foo</code></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><font size="-1"><i>empty</i></font></td>
<td><span style="background-color: #CCFFCC"><code>c:foo</code><br><code>foo</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:foo</code><br><code>foo</code></span></td>
</tr>
<tr>
<td><code>c:/foo</code></td>
<td><span style="background-color: #CCFFCC"><code>c:,foo</code><br><code>c:,/,foo</code></span></td>
<td><code>c:/foo</code></td>
<td><code>c:/foo</code></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:/</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>/</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:/foo</code><br><code>foo</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:</code><br><code>c:/</code></span></td>
<td><code>foo</code></td>
</tr>
<tr>
<td><code>c:foo/</code></td>
<td><span style="background-color: #CCFFCC"><code>c:foo,.</code><br><code>c:,foo,.</code></span></td>
<td><code>c:foo/</code></td>
<td><code>c:foo/</code></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><font size="-1"><i>empty</i></font></td>
<td><span style="background-color: #CCFFCC"><code>c:foo/</code><br><code>foo/</code></span></td>
<td><code>c:foo</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>c:/foo/</code></td>
<td><span style="background-color: #CCFFCC"><code>c:,foo,.</code><br><code>c:,/,foo,.</code></span></td>
<td><code>c:/foo/</code></td>
<td><code>c:/foo/</code></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:/</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>/</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:/foo/</code><br><code>foo/</code></span></td>
<td><code>c:/foo</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>c:/foo/bar</code></td>
<td><span style="background-color: #CCFFCC"><code>c:,foo,bar</code><br><code>c:,/,foo,bar</code></span></td>
<td><code>c:/foo/bar</code></td>
<td><code>c:/foo/bar</code></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:/</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>/</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:/foo/bar</code><br><code>foo/bar</code></span></td>
<td><code>c:/foo</code></td>
<td><code>bar</code></td>
</tr>
<tr>
<td><code>prn:</code></td>
<td><code>prn:</code></td>
<td><code>prn:</code></td>
<td><code>prn:</code></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>prn:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>prn:</code></span></td>
<td><font size="-1"><i>empty</i></font></td>
<td><span style="background-color: #CCFFCC"><code>prn:</code><br><font size="-1"><i>empty</i></font></span></td>
<td><font size="-1"><i>empty</i></font></td>
<td><code>prn:</code></td>
</tr>
<tr>
<td><code>c:\</code></td>
<td><span style="background-color: #CCFFCC"><code>c:\</code><br><code>c:,/</code></span></td>
<td><code>c:\</code></td>
<td><span style="background-color: #CCFFCC"><code>c:\</code><br><code>c:/</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:\</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>\</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:\</code><br><font size="-1"><i>empty</i></font></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:\</code><br><code>\</code></span></td>
</tr>
<tr>
<td><code>c:foo</code></td>
<td><span style="background-color: #CCFFCC"><code>c:foo</code><br><code>c:,foo</code></span></td>
<td><code>c:foo</code></td>
<td><code>c:foo</code></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><font size="-1"><i>empty</i></font></td>
<td><span style="background-color: #CCFFCC"><code>c:foo</code><br><code>foo</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:foo</code><br><code>foo</code></span></td>
</tr>
<tr>
<td><code>c:\foo</code></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo</code><br><code>c:,/,foo</code></span></td>
<td><code>c:\foo</code></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo</code><br><code>c:/foo</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:\</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>\</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo</code><br><code>foo</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:\</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo</code><br><code>foo</code></span></td>
</tr>
<tr>
<td><code>c:foo\</code></td>
<td><span style="background-color: #CCFFCC"><code>c:foo\</code><br><code>c:,foo,.</code></span></td>
<td><code>c:foo\</code></td>
<td><span style="background-color: #CCFFCC"><code>c:foo\</code><br><code>c:foo/</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><font size="-1"><i>empty</i></font></td>
<td><span style="background-color: #CCFFCC"><code>c:foo\</code><br><code>foo\</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:foo</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:foo\</code><br><code>.</code></span></td>
</tr>
<tr>
<td><code>c:\foo\</code></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo\</code><br><code>c:,/,foo,.</code></span></td>
<td><code>c:\foo\</code></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo\</code><br><code>c:/foo/</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:\</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>\</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo\</code><br><code>foo\</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:\foo</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo\</code><br><code>.</code></span></td>
</tr>
<tr>
<td><code>c:\foo/</code></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo,.</code><br><code>c:,/,foo,.</code></span></td>
<td><code>c:\foo/</code></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo/</code><br><code>c:/foo/</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:\</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>\</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:\foo/</code><br><code>foo/</code></span></td>
<td><code>c:\foo</code></td>
<td><code>.</code></td>
</tr>
<tr>
<td><code>c:/foo\bar</code></td>
<td><span style="background-color: #CCFFCC"><code>c:,foo\bar</code><br><code>c:,/,foo,bar</code></span></td>
<td><code>c:/foo\bar</code></td>
<td><span style="background-color: #CCFFCC"><code>c:/foo\bar</code><br><code>c:/foo/bar</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:/</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>c:</code></span></td>
<td><span style="background-color: #CCFFCC"><font size="-1"><i>empty</i></font><br><code>/</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:/foo\bar</code><br><code>foo\bar</code></span></td>
<td><span style="background-color: #CCFFCC"><code>c:</code><br><code>c:/foo</code></span></td>
<td><span style="background-color: #CCFFCC"><code>foo\bar</code><br><code>bar</code></span></td>
</tr>
</table>
<h2><a name="long-path-warning"></a>Warning: Long paths on Windows and the 
extended-length <b>\\?\ </b>prefix</h2>
<p>The Microsoft Windows &quot;Maximum Path Length Limitation&quot; specifies:</p>
<blockquote>
<p>In the Windows API (with some exceptions ...), the maximum length for a path 
is MAX_PATH, which is defined as 260 characters.</p>
<p>The Windows API has many functions that also have Unicode versions to permit 
an extended-length path for a maximum total path length of 32,767 characters. 
... To specify an extended-length path, use the <b>&quot;\\?\&quot; prefix</b>. For 
example, &quot;\\?\D:\<em>very long path</em>&quot;.&nbsp;
<i>[C++ string literals require backslashes be doubled, of course.]</i></p>
</blockquote>
<p>Because most Boost.Filesystem operational functions just pass the contents of 
a class path object to the Windows API, they do work with the extended-length 
prefixes. But some won't work, because to the limitations imposed by Windows. 
Read the following cautions carefully!</p>
<h3>Cautions for paths with extended-length prefixes</h3>
<ul>
  <li>Individual components of a path are still are limited to whatever is 
  supported for the particular filesystem, commonly 255 characters.</li>
  <li>Only backslashes only are acceptable as directory separators. Slashes are 
  not treated as separators.</li>
  <li>All paths must be absolute - relative paths are not allowed.</li>
  <li>Once an absolute path grows beyond 260 characters, it is essentially 
  poisoned and all operations must use extended-length prefixes. So even a 
  simple operation like <code>create_directory(&quot;a&quot;)</code> will fail if the 
  absolute path of the resulting directory would exceed 260 characters.</li>
  <li>Certain Boost.Filesystem functions that decompose their argument path and 
  then work on individual relative directories or files will not work properly 
  with extended-length prefix paths.</li>
</ul>
<h2><a name="Acknowledgements">Acknowledgements</a></h2>
<p>This Filesystem Library is dedicated to my wife, Sonda, who provided the 
support necessary to see both a trial implementation and the proposal itself 
through to completion. She gave me the strength to continue after a difficult 
year of cancer treatment in the middle of it all.</p>
<p>Many people contributed technical comments, ideas, and suggestions to the 
Boost Filesystem Library. See
<a href="http://www.boost.org/libs/filesystem/doc/index.htm#Acknowledgements">
http://www.boost.org/libs/filesystem/doc/index.htm#Acknowledgements</a>.</p>
<p>Dietmar Kuehl contributed the original Boost Filesystem Library directory_iterator design. Peter Dimov, Walter Landry, Rob Stewart, and Thomas 
Witt were particularly helpful in refining the library.</p>
<p>The create_directories, extension, basename, and replace_extension functions 
were developed by Vladimir Prus. The temp_directory_path function was 
contributed by Jeff Flinn. David Svoboda suggested the canonical function and 
provided psuedo-code.</p>
<p>Howard Hinnant and John Maddock reviewed a draft of the version 2 proposal, and 
identified a number of mistakes or weaknesses, resulting in a more polished 
final document.</p>
<p>Peter Dimov suggested a single class path, with member templates to adapt to 
multiple string types. His idea became the basis for the version 3 path design.</p>
<h2><a name="References">References</a></h2>
<table border="0" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="100%">
  <tr>
    <td width="16%" valign="top">[<a name="ISO_POSIX">ISO-POSIX</a>]</td>
    <td width="84%">ISO/IEC 9945:2003, IEEE&nbsp;Std&nbsp;1003.1-2001, and The Open Group 
    Base Specifications, Issue 6. Also known as The Single Unix<font face="Times New Roman"> 
    Specification, Version 3. Available from each of the organizations involved 
    in its creation. For example, read online or download from
    <a href="http://www.unix.org/single_unix_specification/">
    www.unix.org/single_unix_specification/</a>.</font> The ISO JTC1/SC22/WG15 - 
    POSIX homepage is <a href="http://www.open-std.org/jtc1/sc22/WG15/">
    www.open-std.org/jtc1/sc22/WG15/</a></td>
  </tr>
  <tr>
    <td width="16%" valign="top">[Abrahams]</td>
    <td width="84%">Dave Abrahams, Error and Exception Handling,
    <a href="http://www.boost.org/more/error_handling.html">
    www.boost.org/more/error_handling.html</a></td>
  </tr>
</table>
<hr>


</body>

</html>