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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>nftw</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="nftw"></a> <a name="tag_03_405"></a><!-- nftw --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_405_01"></a>NAME</h4><blockquote>nftw - walk a file tree</blockquote><h4><a name="tag_03_405_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/ftw.h.html">ftw.h</a>><br><br> int nftw(const char *</tt><i>path</i><tt>, int (*</tt><i>fn</i><tt>)(const char *,<br> const struct stat *, int, struct FTW *), int</tt> <i>fd_limit</i><tt>, int</tt><i>flags</i><tt>);<br> <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div></blockquote><h4><a name="tag_03_405_03"></a>DESCRIPTION</h4><blockquote><p>The <i>nftw</i>() function shall recursively descend the directory hierarchy rooted in <i>path</i>. The <i>nftw</i>() functionhas a similar effect to <a href="../functions/ftw.html"><i>ftw</i>()</a> except that it takes an additional argument <i>flags</i>,which is a bitwise-inclusive OR of zero or more of the following flags:</p><dl compact><dt>FTW_CHDIR</dt><dd>If set, <i>nftw</i>() shall change the current working directory to each directory as it reports files in that directory. Ifclear, <i>nftw</i>() shall not change the current working directory.</dd><dt>FTW_DEPTH</dt><dd>If set, <i>nftw</i>() shall report all files in a directory before reporting the directory itself. If clear, <i>nftw</i>()shall report any directory before reporting the files in that directory.</dd><dt>FTW_MOUNT</dt><dd>If set, <i>nftw</i>() shall only report files in the same file system as <i>path</i>. If clear, <i>nftw</i>() shall report allfiles encountered during the walk.</dd><dt>FTW_PHYS</dt><dd>If set, <i>nftw</i>() shall perform a physical walk and shall not follow symbolic links.</dd></dl><p>If FTW_PHYS is clear and FTW_DEPTH is set, <i>nftw</i>() shall follow links instead of reporting them, but shall not report anydirectory that would be a descendant of itself. If FTW_PHYS is clear and FTW_DEPTH is clear, <i>nftw</i>() shall follow linksinstead of reporting them, but shall not report the contents of any directory that would be a descendant of itself.</p><p>At each file it encounters, <i>nftw</i>() shall call the user-supplied function <i>fn</i> with four arguments:</p><ul><li><p>The first argument is the pathname of the object.</p></li><li><p>The second argument is a pointer to the <b>stat</b> buffer containing information on the object.</p></li><li><p>The third argument is an integer giving additional information. Its value is one of the following:</p><dl compact><dt>FTW_F</dt><dd>The object is a file.</dd><dt>FTW_D</dt><dd>The object is a directory.</dd><dt>FTW_DP</dt><dd>The object is a directory and subdirectories have been visited. (This condition shall only occur if the FTW_DEPTH flag isincluded in <i>flags</i>.)</dd><dt>FTW_SL</dt><dd>The object is a symbolic link. (This condition shall only occur if the FTW_PHYS flag is included in <i>flags</i>.)</dd><dt>FTW_SLN</dt><dd>The object is a symbolic link that does not name an existing file. (This condition shall only occur if the FTW_PHYS flag is notincluded in <i>flags</i>.)</dd><dt>FTW_DNR</dt><dd>The object is a directory that cannot be read. The <i>fn</i> function shall not be called for any of its descendants.</dd><dt>FTW_NS</dt><dd>The <a href="../functions/stat.html"><i>stat</i>()</a> function failed on the object because of lack of appropriate permission.The <b>stat</b> buffer passed to <i>fn</i> is undefined. Failure of <a href="../functions/stat.html"><i>stat</i>()</a> for anyother reason is considered an error and <i>nftw</i>() shall return -1.</dd></dl></li><li><p>The fourth argument is a pointer to an <b>FTW</b> structure. The value of <b>base</b> is the offset of the object's filename inthe pathname passed as the first argument to <i>fn</i>. The value of <b>level</b> indicates depth relative to the root of the walk,where the root level is 0.</p></li></ul><p>The results are unspecified if the application-supplied <i>fn</i> function does not preserve the current working directory.</p><p>The argument <i>fd_limit</i> sets the maximum number of file descriptors that shall be used by <i>nftw</i>() while traversingthe file tree. At most one file descriptor shall be used for each directory level.</p><p>The <i>nftw</i>() function need not be reentrant. A function that is not required to be reentrant is not required to bethread-safe.</p></blockquote><h4><a name="tag_03_405_04"></a>RETURN VALUE</h4><blockquote><p>The <i>nftw</i>() function shall continue until the first of the following conditions occurs:</p><ul><li><p>An invocation of <i>fn</i> shall return a non-zero value, in which case <i>nftw</i>() shall return that value.</p></li><li><p>The <i>nftw</i>() function detects an error other than [EACCES] (see FTW_DNR and FTW_NS above), in which case <i>nftw</i>()shall return -1 and set <i>errno</i> to indicate the error.</p></li><li><p>The tree is exhausted, in which case <i>nftw</i>() shall return 0.</p></li></ul></blockquote><h4><a name="tag_03_405_05"></a>ERRORS</h4><blockquote><p>The <i>nftw</i>() function shall fail if:</p><dl compact><dt>[EACCES]</dt><dd>Search permission is denied for any component of <i>path</i> or read permission is denied for <i>path</i>, or <i>fn</i> returns-1 and does not reset <i>errno</i>.</dd><dt>[ELOOP]</dt><dd>A loop exists in symbolic links encountered during resolution of the <i>path</i> argument.</dd><dt>[ENAMETOOLONG]</dt><dd>The length of the <i>path</i> argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.</dd><dt>[ENOENT]</dt><dd>A component of <i>path</i> does not name an existing file or <i>path</i> is an empty string.</dd><dt>[ENOTDIR]</dt><dd>A component of <i>path</i> is not a directory.</dd><dt>[EOVERFLOW]</dt><dd>A field in the <b>stat</b> structure cannot be represented correctly in the current programming environment for one or morefiles found in the file hierarchy.</dd></dl><p>The <i>nftw</i>() function may fail if:</p><dl compact><dt>[ELOOP]</dt><dd>More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the <i>path</i> argument.</dd><dt>[EMFILE]</dt><dd>{OPEN_MAX} file descriptors are currently open in the calling process.</dd><dt>[ENAMETOOLONG]</dt><dd>Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.</dd><dt>[ENFILE]</dt><dd>Too many files are currently open in the system.</dd></dl><p>In addition, <i>errno</i> may be set if the function pointed to by <i>fn</i> causes <i>errno</i> to be set.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_405_06"></a>EXAMPLES</h4><blockquote><p>The following example walks the <b>/tmp</b> directory and its subdirectories, calling the <i>nftw</i>() function for everydirectory entry, using a maximum of 5 file descriptors.</p><pre><tt>#include <ftw.h>...int nftwfunc(const char *, const struct stat *, int, struct FTW *);<br>int nftwfunc(const char *filename, const struct stat *statptr, int fileflags, struct FTW *pfwt){ return 0;}...char *startpath = "/tmp";int fd_limit = 5;int flags = FTW_CHDIR | FTW_DEPTH | FTW_MOUNT;int ret;<br>ret = nftw(startpath, nftwfunc, fd_limit, flags);</tt></pre></blockquote><h4><a name="tag_03_405_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_405_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_405_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_405_10"></a>SEE ALSO</h4><blockquote><p><a href="lstat.html"><i>lstat</i>()</a>, <a href="opendir.html"><i>opendir</i>()</a>, <a href="readdir.html"><i>readdir</i>()</a>, <a href="stat.html"><i>stat</i>()</a>, the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/ftw.h.html"><i><ftw.h></i></a></p></blockquote><h4><a name="tag_03_405_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 4, Version 2.</p></blockquote><h4><a name="tag_03_405_12"></a>Issue 5</h4><blockquote><p>Moved from X/OPEN UNIX extension to BASE.</p><p>In the DESCRIPTION, the definition of the <i>depth</i> argument is clarified.</p></blockquote><h4><a name="tag_03_405_13"></a>Issue 6</h4><blockquote><p>The Open Group Base Resolution bwg97-003 is applied.</p><p>The ERRORS section is updated as follows:</p><ul><li><p>The wording of the mandatory [ELOOP] error condition is updated.</p></li><li><p>A second optional [ELOOP] error condition is added.</p></li><li><p>The [EOVERFLOW] mandatory error condition is added.</p></li></ul><p>Text is added to the DESCRIPTION to say that the <i>nftw</i>() function need not be reentrant and that the results areunspecified if the application-supplied <i>fn</i> function does not preserve the current working directory.</p><p>IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/64 is applied, changing the argument <i>depth</i> to<i>fd_limit</i> throughout and changing ``to a maximum of 5 levels deep'' to ``using a maximum of 5 file descriptors'' in theEXAMPLES section.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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