chmod.html
来自「unix 下的C开发手册,还用详细的例程。」· HTML 代码 · 共 184 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>chmod</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_001_440"> </a>NAME</h4><blockquote>chmod - change mode of a file</blockquote><h4><a name = "tag_000_001_441"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="systypes.h.html">sys/types.h</a>>#include <<a href="sysstat.h.html">sys/stat.h</a>>int chmod(const char *<i>path</i>, mode_t <i>mode</i>);</code></pre></blockquote><h4><a name = "tag_000_001_442"> </a>DESCRIPTION</h4><blockquote>The<i>chmod()</i>function changes S_ISUID, S_ISGID,S_ISVTXand the file permission bits of thefile named by the pathname pointed to by the<i>path</i>argument to the corresponding bits in the<i>mode</i>argument.The effective user ID of the process must match theowner of the file or the process must have appropriate privilegesin order to do this.<p>S_ISUID, S_ISGID and the file permission bitsare described in<i><a href="sysstat.h.html"><sys/stat.h></a></i>.<p>If a directory is writable and the mode bit S_ISVTX is set onthe directory, a process may remove or rename files within thatdirectory only if one or more of the following is true:<ul><p><li>The effective user ID of the process is the same as that of the owner ID ofthe file.<p><li>The effective user ID of the process is the same as that of the owner ID ofthe directory.<p><li>The process has appropriate privileges.<p></ul><p>If the S_ISVTX bit is set on a non-directory file, the behaviour isunspecified.<p>If the calling process does not have appropriate privileges,and if the group IDof the file does not match the effective group IDor one of the supplementary groupIDs and if the file is a regular file, bit S_ISGID (set-group-IDon execution) in the file's mode will be cleared upon successful returnfrom<i>chmod()</i>.<p>Additional implementation-dependent restrictions may cause the S_ISUIDand S_ISGID bits in<i>mode</i>to be ignored.<p>The effect on file descriptors for files open at the time of a call to<i>chmod()</i>is implementation-dependent.<p>Upon successful completion,<i>chmod()</i>will mark for update the<i>st_ctime</i>field of the file.</blockquote><h4><a name = "tag_000_001_443"> </a>RETURN VALUE</h4><blockquote>Upon successful completion, 0 is returned. Otherwise, -1 is returned and<i>errno</i>is set to indicate the error.If -1 is returned, no change to the file mode will occur.</blockquote><h4><a name = "tag_000_001_444"> </a>ERRORS</h4><blockquote>The<i>chmod()</i>function will fail if:<dl compact><dt>[EACCES]<dd>Search permission is denied on a component of the path prefix.<dt>[ELOOP]<dd>Too many symbolic links were encountered in resolving <i>path</i>.<dt>[ENAMETOOLONG]<dd>The length of the<i>path</i>argument exceeds {PATH_MAX} or a pathname component is longer than{NAME_MAX}.<dt>[ENOTDIR]<dd>A component of the path prefix is not a directory.<dt>[ENOENT]<dd>A component of <i>path</i> does not name an existing fileor <i>path</i> is an empty string.<dt>[EPERM]<dd>The effective user IDdoes not match the owner of the file and theprocess does not have appropriate privileges.<dt>[EROFS]<dd>The named file resides on a read-only file system.</dl><p>The<i>chmod()</i>functionmay fail if:<dl compact><dt>[EINTR]<dd>A signal was caught during execution of the function.<dt>[EINVAL]<dd>The value of the<i>mode</i>argument is invalid.<dt>[ENAMETOOLONG]<dd>Pathname resolution of a symbolic link produced an intermediate result whoselength exceeds {PATH_MAX}.</dl></blockquote><h4><a name = "tag_000_001_445"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_001_446"> </a>APPLICATION USAGE</h4><blockquote>In order to ensure that the S_ISUID and S_ISGIDbits are set, an application requiring this should use<i><a href="stat.html">stat()</a></i>after a successful<i>chmod()</i>to verify this.<p>Any file descriptors currently open by any process on the file may becomeinvalid if the mode of the file is changed to a value which would deny accessto that process. One situation where this could occur is on a statelessfile system.</blockquote><h4><a name = "tag_000_001_447"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_001_448"> </a>SEE ALSO</h4><blockquote><i><a href="chown.html">chown()</a></i>,<i><a href="mkdir.html">mkdir()</a></i>,<i><a href="mkfifo.html">mkfifo()</a></i>,<i><a href="open.html">open()</a></i>,<i><a href="stat.html">stat()</a></i>,<i><a href="statvfs.html">statvfs()</a></i>,<i><a href="sysstat.h.html"><sys/stat.h></a></i>,<i><a href="systypes.h.html"><sys/types.h></a></i>.</blockquote><h4>DERIVATION</h4><blockquote>Derived from Issue 1 of the SVID.</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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