| <html lang="en"> |
| <head> |
| <title>Reading/Closing Directory - The GNU C Library</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="The GNU C Library"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Accessing-Directories.html#Accessing-Directories" title="Accessing Directories"> |
| <link rel="prev" href="Opening-a-Directory.html#Opening-a-Directory" title="Opening a Directory"> |
| <link rel="next" href="Simple-Directory-Lister.html#Simple-Directory-Lister" title="Simple Directory Lister"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| This file documents the GNU C library. |
| |
| This is Edition 0.12, last updated 2007-10-27, |
| of `The GNU C Library Reference Manual', for version |
| 2.8 (Sourcery G++ Lite 2011.03-41). |
| |
| Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002, |
| 2003, 2007, 2008, 2010 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being ``Free Software Needs Free Documentation'' |
| and ``GNU Lesser General Public License'', the Front-Cover texts being |
| ``A GNU Manual'', and with the Back-Cover Texts as in (a) below. A |
| copy of the license is included in the section entitled "GNU Free |
| Documentation License". |
| |
| (a) The FSF's Back-Cover Text is: ``You have the freedom to |
| copy and modify this GNU manual. Buying copies from the FSF |
| supports it in developing GNU and promoting software freedom.''--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Reading%2fClosing-Directory"></a> |
| <a name="Reading_002fClosing-Directory"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Simple-Directory-Lister.html#Simple-Directory-Lister">Simple Directory Lister</a>, |
| Previous: <a rel="previous" accesskey="p" href="Opening-a-Directory.html#Opening-a-Directory">Opening a Directory</a>, |
| Up: <a rel="up" accesskey="u" href="Accessing-Directories.html#Accessing-Directories">Accessing Directories</a> |
| <hr> |
| </div> |
| |
| <h4 class="subsection">14.2.3 Reading and Closing a Directory Stream</h4> |
| |
| <p><a name="index-dirent_002eh-1416"></a>This section describes how to read directory entries from a directory |
| stream, and how to close the stream when you are done with it. All the |
| symbols are declared in the header file <samp><span class="file">dirent.h</span></samp>. |
| |
| <!-- dirent.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: struct dirent * <b>readdir</b> (<var>DIR *dirstream</var>)<var><a name="index-readdir-1417"></a></var><br> |
| <blockquote><p>This function reads the next entry from the directory. It normally |
| returns a pointer to a structure containing information about the file. |
| This structure is statically allocated and can be rewritten by a |
| subsequent call. |
| |
| <p><strong>Portability Note:</strong> On some systems <code>readdir</code> may not |
| return entries for <samp><span class="file">.</span></samp> and <samp><span class="file">..</span></samp>, even though these are always |
| valid file names in any directory. See <a href="File-Name-Resolution.html#File-Name-Resolution">File Name Resolution</a>. |
| |
| <p>If there are no more entries in the directory or an error is detected, |
| <code>readdir</code> returns a null pointer. The following <code>errno</code> error |
| conditions are defined for this function: |
| |
| <dl> |
| <dt><code>EBADF</code><dd>The <var>dirstream</var> argument is not valid. |
| </dl> |
| |
| <p><code>readdir</code> is not thread safe. Multiple threads using |
| <code>readdir</code> on the same <var>dirstream</var> may overwrite the return |
| value. Use <code>readdir_r</code> when this is critical. |
| </p></blockquote></div> |
| |
| <!-- dirent.h --> |
| <!-- GNU --> |
| <div class="defun"> |
| — Function: int <b>readdir_r</b> (<var>DIR *dirstream, struct dirent *entry, struct dirent **result</var>)<var><a name="index-readdir_005fr-1418"></a></var><br> |
| <blockquote><p>This function is the reentrant version of <code>readdir</code>. Like |
| <code>readdir</code> it returns the next entry from the directory. But to |
| prevent conflicts between simultaneously running threads the result is |
| not stored in statically allocated memory. Instead the argument |
| <var>entry</var> points to a place to store the result. |
| |
| <p>Normally <code>readdir_r</code> returns zero and sets <code>*</code><var>result</var> |
| to <var>entry</var>. If there are no more entries in the directory or an |
| error is detected, <code>readdir_r</code> sets <code>*</code><var>result</var> to a |
| null pointer and returns a nonzero error code, also stored in |
| <code>errno</code>, as described for <code>readdir</code>. |
| |
| <p><strong>Portability Note:</strong> On some systems <code>readdir_r</code> may not |
| return a NUL terminated string for the file name, even when there is no |
| <code>d_reclen</code> field in <code>struct dirent</code> and the file |
| name is the maximum allowed size. Modern systems all have the |
| <code>d_reclen</code> field, and on old systems multi-threading is not |
| critical. In any case there is no such problem with the <code>readdir</code> |
| function, so that even on systems without the <code>d_reclen</code> member one |
| could use multiple threads by using external locking. |
| |
| <p>It is also important to look at the definition of the <code>struct |
| dirent</code> type. Simply passing a pointer to an object of this type for |
| the second parameter of <code>readdir_r</code> might not be enough. Some |
| systems don't define the <code>d_name</code> element sufficiently long. In |
| this case the user has to provide additional space. There must be room |
| for at least <code>NAME_MAX + 1</code> characters in the <code>d_name</code> array. |
| Code to call <code>readdir_r</code> could look like this: |
| |
| <pre class="smallexample"> union |
| { |
| struct dirent d; |
| char b[offsetof (struct dirent, d_name) + NAME_MAX + 1]; |
| } u; |
| |
| if (readdir_r (dir, &u.d, &res) == 0) |
| ... |
| </pre> |
| </blockquote></div> |
| |
| <p>To support large filesystems on 32-bit machines there are LFS variants |
| of the last two functions. |
| |
| <!-- dirent.h --> |
| <!-- LFS --> |
| <div class="defun"> |
| — Function: struct dirent64 * <b>readdir64</b> (<var>DIR *dirstream</var>)<var><a name="index-readdir64-1419"></a></var><br> |
| <blockquote><p>The <code>readdir64</code> function is just like the <code>readdir</code> function |
| except that it returns a pointer to a record of type <code>struct |
| dirent64</code>. Some of the members of this data type (notably <code>d_ino</code>) |
| might have a different size to allow large filesystems. |
| |
| <p>In all other aspects this function is equivalent to <code>readdir</code>. |
| </p></blockquote></div> |
| |
| <!-- dirent.h --> |
| <!-- LFS --> |
| <div class="defun"> |
| — Function: int <b>readdir64_r</b> (<var>DIR *dirstream, struct dirent64 *entry, struct dirent64 **result</var>)<var><a name="index-readdir64_005fr-1420"></a></var><br> |
| <blockquote><p>The <code>readdir64_r</code> function is equivalent to the <code>readdir_r</code> |
| function except that it takes parameters of base type <code>struct |
| dirent64</code> instead of <code>struct dirent</code> in the second and third |
| position. The same precautions mentioned in the documentation of |
| <code>readdir_r</code> also apply here. |
| </p></blockquote></div> |
| |
| <!-- dirent.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: int <b>closedir</b> (<var>DIR *dirstream</var>)<var><a name="index-closedir-1421"></a></var><br> |
| <blockquote><p>This function closes the directory stream <var>dirstream</var>. It returns |
| <code>0</code> on success and <code>-1</code> on failure. |
| |
| <p>The following <code>errno</code> error conditions are defined for this |
| function: |
| |
| <dl> |
| <dt><code>EBADF</code><dd>The <var>dirstream</var> argument is not valid. |
| </dl> |
| </p></blockquote></div> |
| |
| </body></html> |
| |
