nftw.html
来自「unix 下的C开发手册,还用详细的例程。」· HTML 代码 · 共 243 行
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>nftw</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_007_883"> </a>NAME</h4><blockquote>nftw - walk a file tree</blockquote><h4><a name = "tag_000_007_884"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="ftw.h.html">ftw.h</a>>int nftw(const char *<i>path</i>, int (*<i>fn</i>)(const char *, const struct stat *, int, struct FTW *), int <i>depth</i>, int <i>flags</i>);</code></pre></blockquote><h4><a name = "tag_000_007_885"> </a>DESCRIPTION</h4><blockquote>The<i>nftw()</i>function recursively descends the directory hierarchy rooted in<i>path</i>.The<i>nftw()</i>function has a similar effect to<i><a href="ftw.html">ftw()</a></i>except that it takes an additional argument <i>flags</i>, which isa bitwise inclusive-OR of zero or more of the following flags:<dl compact><dt>FTW_CHDIR<dd>If set,<i>nftw()</i>will change the current working directory to each directory as itreports files in that directory. If clear,<i>nftw()</i>will not change the current working directory.<dt>FTW_DEPTH<dd>If set,<i>nftw()</i>will report all files in a directory before reporting the directory itself.If clear,<i>nftw()</i>will report any directory before reporting the files in that directory.<dt>FTW_MOUNT<dd>If set,<i>nftw()</i>will only report files in the same file system as<i>path</i>.If clear,<i>nftw()</i>will report all files encountered during the walk.<dt>FTW_PHYS<dd>If set,<i>nftw()</i>performs a physical walk and does not follow symbolic links. If clear,<i>nftw()</i>will follow links instead of reporting them,and will not report the same file twice.</dl><p>At each file it encounters,<i>nftw()</i>calls the user-supplied function<i>fn()</i>with four arguments:<ul><p><li>The first argument is the pathname of the object.<p><li>The second argument is a pointer to the <b>stat</b> buffer containinginformation on the object.<p><li>The third argument is an integer giving additional information. Its value isone of the following:<dl compact><dt>FTW_F<dd>The object is a file.<dt>FTW_D<dd>The object is a directory.<dt>FTW_DP<dd>The object is a directory and subdirectories have been visited.(This condition will only occur if the FTW_DEPTH flag isincluded in <i>flags</i>.)<dt>FTW_SL<dd>The object is a symbolic link.(This condition will only occur if the FTW_PHYS flag isincluded in <i>flags</i>.)<dt>FTW_SLN<dd>The object is a symbolic link that does not name an existing file.(This condition will only occur if the FTW_PHYS flag is notincluded in <i>flags</i>.)<dt>FTW_DNR<dd>The object is a directory that cannot be read. The<i>fn()</i>function will not be called for any of its descendants.<dt>FTW_NS<dd>The<i><a href="stat.html">stat()</a></i>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<i><a href="stat.html">stat()</a></i>for any other reason is considered an error and<i>nftw()</i>returns -1.</dl><p><li>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 in thepathname passed as the first argument to<i>fn()</i>.The value of <b>level</b> indicates depth relative to the root of of the walk,where the root level is 0.<p></ul><p>The argument <i>depth</i> sets the maximum number of file descriptors thatwill be used by <i>nftw()</i>while traversing the file tree. At most one filedescriptor will be used for each directory level.</blockquote><h4><a name = "tag_000_007_886"> </a>RETURN VALUE</h4><blockquote>The<i>nftw()</i>function continues until the first of the following conditions occurs:<ul><p><li>An invocation of<i>fn()</i>returns a non-zero value, in which case<i>nftw()</i>returns that value.<p><li>The<i>nftw()</i>function detects an error other than [EACCES] (see FTW_DNR and FTW_NS above),in which case<i>nftw()</i>returns -1 and sets <i>errno</i> to indicate the error.<p><li>The tree is exhausted, in which case<i>nftw()</i>returns 0.<p></ul></blockquote><h4><a name = "tag_000_007_887"> </a>ERRORS</h4><blockquote>The<i>nftw()</i>function will fail if:<dl compact><dt>[EACCES]<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>.<dt>[ENAMETOOLONG]<dd>The length of the <i>path</i> string exceeds {PATH_MAX}, or apathname component is longer than {NAME_MAX}.<dt>[ENOENT]<dd>A component of <i>path</i> does not name an existing fileor <i>path</i> is an empty string.<dt>[ENOTDIR]<dd>A component of <i>path</i> is not a directory.</dl><p>The<i>nftw()</i>function may fail if:<dl compact><dt>[ELOOP]<dd>Too many symbolic links were encountered in resolving <i>path</i>.<dt>[EMFILE]<dd>{OPEN_MAX} file descriptors are currently open in the calling process.<dt>[ENAMETOOLONG]<dd>Pathname resolution of a symbolic link produced an intermediate result whoselength exceeds {PATH_MAX}.<dt>[ENFILE]<dd>Too many files are currently open in the system.</dl><p>In addition, <i>errno</i> may be set if the function pointed by<i>fn()</i>causes <i>errno</i> to be set.</blockquote><h4><a name = "tag_000_007_888"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_889"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_890"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_891"> </a>SEE ALSO</h4><blockquote><i><a href="lstat.html">lstat()</a></i>,<i><a href="opendir.html">opendir()</a></i>,<i><a href="readdir.html">readdir()</a></i>,<i><a href="stat.html">stat()</a></i>,<i><a href="ftw.h.html"><ftw.h></a></i>.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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