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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) 2001-2003 The Open Group, All Rights Reserved --><title>ftw</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="ftw"></a> <a name="tag_03_201"></a><!-- ftw --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_201_01"></a>NAME</h4><blockquote>ftw - traverse (walk) a file tree</blockquote><h4><a name="tag_03_201_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 ftw(const char *</tt><i>path</i><tt>, int (*</tt><i>fn</i><tt>)(const char *,<br> const struct stat *</tt><i>ptr</i><tt>, int</tt> <i>flag</i><tt>), int</tt><i>ndirs</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_201_03"></a>DESCRIPTION</h4><blockquote><p>The <i>ftw</i>() function shall recursively descend the directory hierarchy rooted in <i>path</i>. For each object in thehierarchy, <i>ftw</i>() shall call the function pointed to by <i>fn</i>, passing it a pointer to a null-terminated character stringcontaining the name of the object, a pointer to a <b>stat</b> structure containing information about the object, and an integer.Possible values of the integer, defined in the <a href="../basedefs/ftw.h.html"><i><ftw.h></i></a> header, are:</p><dl compact><dt>FTW_D</dt><dd>For a directory.</dd><dt>FTW_DNR</dt><dd>For a directory that cannot be read.</dd><dt>FTW_F</dt><dd>For a file.</dd><dt>FTW_SL</dt><dd>For a symbolic link (but see also FTW_NS below).</dd><dt>FTW_NS</dt><dd>For an object other than a symbolic link on which <a href="../functions/stat.html"><i>stat</i>()</a> could not successfully beexecuted. If the object is a symbolic link and <a href="../functions/stat.html"><i>stat</i>()</a> failed, it is unspecified whether<i>ftw</i>() passes FTW_SL or FTW_NS to the user-supplied function.</dd></dl><p>If the integer is FTW_DNR, descendants of that directory shall not be processed. If the integer is FTW_NS, the <b>stat</b>structure contains undefined values. An example of an object that would cause FTW_NS to be passed to the function pointed to by<i>fn</i> would be a file in a directory with read but without execute (search) permission.</p><p>The <i>ftw</i>() function shall visit a directory before visiting any of its descendants.</p><p>The <i>ftw</i>() function shall use at most one file descriptor for each level in the tree.</p><p>The argument <i>ndirs</i> should be in the range [1, {OPEN_MAX}].</p><p>The tree traversal shall continue until either the tree is exhausted, an invocation of <i>fn</i> returns a non-zero value, orsome error, other than [EACCES], is detected within <i>ftw</i>().</p><p>The <i>ndirs</i> argument shall specify the maximum number of directory streams or file descriptors or both available for use by<i>ftw</i>() while traversing the tree. When <i>ftw</i>() returns it shall close any directory streams and file descriptors it usesnot counting any opened by the application-supplied <i>fn</i> function.</p><p>The results are unspecified if the application-supplied <i>fn</i> function does not preserve the current working directory.</p><p>The <i>ftw</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_201_04"></a>RETURN VALUE</h4><blockquote><p>If the tree is exhausted, <i>ftw</i>() shall return 0. If the function pointed to by <i>fn</i> returns a non-zero value,<i>ftw</i>() shall stop its tree traversal and return whatever value was returned by the function pointed to by <i>fn</i>. If<i>ftw</i>() detects an error, it shall return -1 and set <i>errno</i> to indicate the error.</p><p>If <i>ftw</i>() encounters an error other than [EACCES] (see FTW_DNR and FTW_NS above), it shall return -1 and set <i>errno</i>to indicate the error. The external variable <i>errno</i> may contain any error value that is possible when a directory is openedor when one of the <i>stat</i> functions is executed on a directory or file.</p></blockquote><h4><a name="tag_03_201_05"></a>ERRORS</h4><blockquote><p>The <i>ftw</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>.</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>ftw</i>() function may fail if:</p><dl compact><dt>[EINVAL]</dt><dd>The value of the <i>ndirs</i> argument is invalid.</dd><dt>[ELOOP]</dt><dd>More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the <i>path</i> argument.</dd><dt>[ENAMETOOLONG]</dt><dd>Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.</dd></dl><p>In addition, if the function pointed to by <i>fn</i> encounters system errors, <i>errno</i> may be set accordingly.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_201_06"></a>EXAMPLES</h4><blockquote><h5><a name="tag_03_201_06_01"></a>Walking a Directory Structure</h5><p>The following example walks the current directory structure, calling the <i>fn</i> function for every directory entry, using atmost 10 file descriptors:</p><pre><tt>#include <ftw.h>...if (ftw(".", fn, 10) != 0) { perror("ftw"); exit(2);}</tt></pre></blockquote><h4><a name="tag_03_201_07"></a>APPLICATION USAGE</h4><blockquote><p>The <i>ftw</i>() function may allocate dynamic storage during its operation. If <i>ftw</i>() is forcibly terminated, such as by<a href="../functions/longjmp.html"><i>longjmp</i>()</a> or <a href="../functions/siglongjmp.html"><i>siglongjmp</i>()</a> beingexecuted by the function pointed to by <i>fn</i> or an interrupt routine, <i>ftw</i>() does not have a chance to free that storage,so it remains permanently allocated. A safe way to handle interrupts is to store the fact that an interrupt has occurred, andarrange to have the function pointed to by <i>fn</i> return a non-zero value at its next invocation.</p></blockquote><h4><a name="tag_03_201_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_201_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_201_10"></a>SEE ALSO</h4><blockquote><p><a href="longjmp.html"><i>longjmp</i>()</a> , <a href="lstat.html"><i>lstat</i>()</a> , <a href="malloc.html"><i>malloc</i>()</a> , <a href="nftw.html"><i>nftw</i>()</a> , <a href="opendir.html"><i>opendir</i>()</a> , <a href="siglongjmp.html"><i>siglongjmp</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>, <a href="../basedefs/sys/stat.h.html"><i><sys/stat.h></i></a></p></blockquote><h4><a name="tag_03_201_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><h4><a name="tag_03_201_12"></a>Issue 5</h4><blockquote><p>UX codings in the DESCRIPTION, RETURN VALUE, and ERRORS sections are changed to EX.</p></blockquote><h4><a name="tag_03_201_13"></a>Issue 6</h4><blockquote><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>ftw</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></blockquote><div class="box"><em>End of informative text.</em></div><hr><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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