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Linux系统调用

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<TITLE>Syscall specifications of Linux - chmod</TITLE>
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<H2><A NAME="SEC6" HREF="syscalls_toc.html#SEC6" tppabs="http://personal.xfol.com/%7erezaie/syscall/syscalls_toc.html#SEC6">chmod and fchmod</A></H2>
<P>
<H3>SYNOPSIS</H3>
<P>
<CODE>int chmod(const char *<VAR>path</VAR>, mode_t <VAR>mode</VAR>);</CODE>
<P>
<CODE>int fchmod(int <VAR>fd</VAR>, mode_t <VAR>mode</VAR>);</CODE>
<P>
<H3>PARAMETERS</H3>
<P>
<VAR>path</VAR>: [in] points to the path of the file to modify.
<P>
<VAR>fd</VAR>: [in] the file descriptor to modify.
<P>
<VAR>mode</VAR>: [in] the new mode.
<P>
<H3>DESCRIPTION</H3>
<P>
<CODE>chmod</CODE> changes the mode of the file specified by <VAR>path</VAR> to
<VAR>mode</VAR>. <CODE>fchmod</CODE> changes the mode of the file descriptor
specified by <VAR>fd</VAR> to <VAR>mode</VAR>.The possible values of <VAR>mode</VAR>
are obtained by or'ing the following constants:
<P>
<UL>
<LI><CODE>S_ISUID</CODE>: set uid on execution.
<LI><CODE>S_ISGID</CODE>: set gid on execution.
<LI><CODE>S_ISVTX</CODE>: sticky bit.
<LI><CODE>S_IRUSR</CODE>: readable by owner.
<LI><CODE>S_IWUSR</CODE>: writable by owner.
<LI><CODE>S_IXUSR</CODE>: executable by owner.
<LI><CODE>S_IRGRP</CODE>: readable by group.
<LI><CODE>S_IWGRP</CODE>: writable by group.
<LI><CODE>S_IXGRP</CODE>: executable by group.
<LI><CODE>S_IROTH</CODE>: readable by the world.
<LI><CODE>S_IWOTH</CODE>: writable by the world.
<LI><CODE>S_IXOTH</CODE>: executable by the world.
</UL>
<P>
<H3>RETURN VALUE</H3>
<P>
On success zero is returned. On error, -1 is returned and <CODE>errno</CODE> is
set to one of the following values:
<P>
for <CODE>chmod</CODE>:
<P>
<UL>
<LI><CODE>EPERM</CODE>: the effective uid of the task is not equal the the
uid of the file and the task does not have superuser privileges.
<LI><CODE>ENOTDIR</CODE>, <CODE>EACCESS</CODE>, <CODE>EFAULT</CODE>, <CODE>ENOENT</CODE>,
<CODE>ENOMEM</CODE> <CODE>ENAMETOOLONG</CODE>, <CODE>EROFS</CODE> or <CODE>ELOOP</CODE>.
</UL>
<P>
for <CODE>fchmod</CODE>:
<P>
<UL>
<LI><CODE>EPERM</CODE>: the effective uid of the task is not equal the the
uid of the file and the task does not have superuser privileges.
<LI><CODE>ENOENT</CODE>, <CODE>EROFS</CODE> or <CODE>EBADF</CODE>.
</UL>
<P>
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