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<HTML>
<HEAD>
<TITLE>close(2)</TITLE>
</HEAD>
<BODY>
<H1>close(2)</H1>
<HR>
<PRE>
</PRE>
<H2>NAME</H2><PRE>
close - delete a descriptor
</PRE>
<H2>SYNOPSIS</H2><PRE>
<STRONG>#include</STRONG> <STRONG>&lt;unistd.h&gt;</STRONG>
<STRONG>int</STRONG> <STRONG>close(int</STRONG> <EM>d</EM><STRONG>)</STRONG>
</PRE>
<H2>DESCRIPTION</H2><PRE>
The <STRONG>close</STRONG> call deletes a descriptor from the per-process object reference
table. If this is the last reference to the underlying object, then it
will be deactivated. For example, on the last close of a file the
current <EM>seek</EM> pointer associated with the file is lost; on the last close
of a TCP/IP descriptor associated naming information and queued data are
discarded; on the last close of a file holding an advisory lock the lock
is released (see further <STRONG><A HREF="../man2/fcntl.2.html">fcntl(2)</A></STRONG>).
A close of all of a process's descriptors is automatic on <EM>exit</EM>, but since
there is a limit on the number of active descriptors per process, <STRONG>close</STRONG>
is necessary for programs that deal with many descriptors.
When a process forks (see <STRONG><A HREF="../man2/fork.2.html">fork(2)</A></STRONG>), all descriptors for the new child
process reference the same objects as they did in the parent before the
fork. If a new process is then to be run using <STRONG><A HREF="../man2/execve.2.html">execve(2)</A></STRONG>, the process
would normally inherit these descriptors. Most of the descriptors can be
rearranged with <STRONG><A HREF="../man2/dup2.2.html">dup2(2)</A></STRONG> or deleted with <STRONG>close</STRONG> before the <STRONG>execve</STRONG> is
attempted, but if some of these descriptors will still be needed if the
<STRONG>execve</STRONG> fails, it is necessary to arrange for them to be closed if the
<STRONG>execve</STRONG> succeeds. For this reason, the call ``fcntl(d, F_SETFD, <EM>flags</EM>)''
is provided, that can be used to mark a descriptor "close on exec" by
setting the <STRONG>FD_CLOEXEC</STRONG> flag:
fcntl(d, F_SETFD, fcntl(d, F_GETFD) | FD_CLOEXEC);
</PRE>
<H2>RETURN VALUE</H2><PRE>
Upon successful completion, a value of 0 is returned. Otherwise, a value
of -1 is returned and the global integer variable <STRONG>errno</STRONG> is set to
indicate the error.
</PRE>
<H2>ERRORS</H2><PRE>
<STRONG>Close</STRONG> will fail if:
[EBADF] <EM>D</EM> is not an active descriptor.
</PRE>
<H2>SEE ALSO</H2><PRE>
<STRONG><A HREF="../man2/open.2.html">open(2)</A></STRONG>, <STRONG><A HREF="../man2/pipe.2.html">pipe(2)</A></STRONG>, <STRONG><A HREF="../man2/execve.2.html">execve(2)</A></STRONG>, <STRONG><A HREF="../man2/fcntl.2.html">fcntl(2)</A></STRONG>.
</PRE>
</BODY>
</HTML>