281 lines
6.4 KiB
HTML
281 lines
6.4 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of TEMPNAM</TITLE>
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</HEAD><BODY>
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<H1>TEMPNAM</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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tempnam - create a name for a temporary file
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/stdio.h">stdio.h</A>></B>
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<B>char *tempnam(const char *</B><I>dir</I><B>, const char *</B><I>pfx</I><B>);</B>
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</PRE>
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<P>
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Feature Test Macro Requirements for glibc (see
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<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
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<P>
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<B>tempnam</B>():
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<BR> Since glibc 2.19:
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<BR> _DEFAULT_SOURCE
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<BR> Glibc 2.19 and earlier:
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<BR> _BSD_SOURCE || _SVID_SOURCE
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<I>Never use this function.</I>
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Use
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<B><A HREF="/cgi-bin/man/man2html?3+mkstemp">mkstemp</A></B>(3)
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or
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<B><A HREF="/cgi-bin/man/man2html?3+tmpfile">tmpfile</A></B>(3)
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instead.
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<P>
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The
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<B>tempnam</B>()
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function returns a pointer to a string that is a valid filename,
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and such that a file with this name did not exist when
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<B>tempnam</B>()
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checked.
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The filename suffix of the pathname generated will start with
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<I>pfx</I>
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in case
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<I>pfx</I>
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is a non-NULL string of at most five bytes.
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The directory prefix part of the pathname generated is required to
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be "appropriate" (often that at least implies writable).
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<P>
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Attempts to find an appropriate directory go through the following
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steps:
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<DL COMPACT>
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<DT id="1">a)<DD>
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In case the environment variable
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<B>TMPDIR</B>
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exists and
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contains the name of an appropriate directory, that is used.
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<DT id="2">b)<DD>
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Otherwise, if the
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<I>dir</I>
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argument is non-NULL and appropriate, it is used.
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<DT id="3">c)<DD>
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Otherwise,
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<I>P_tmpdir</I>
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(as defined in
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<I><<A HREF="file:///usr/include/stdio.h">stdio.h</A>></I>)
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is used when appropriate.
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<DT id="4">d)<DD>
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Finally an implementation-defined directory may be used.
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</DL>
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<P>
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The string returned by
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<B>tempnam</B>()
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is allocated using
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<B><A HREF="/cgi-bin/man/man2html?3+malloc">malloc</A></B>(3)
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and hence should be freed by
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<B><A HREF="/cgi-bin/man/man2html?3+free">free</A></B>(3).
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success, the
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<B>tempnam</B>()
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function returns a pointer to a unique temporary filename.
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It returns NULL if a unique name cannot be generated, with
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<I>errno</I>
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set to indicate the cause of the error.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="5"><B>ENOMEM</B>
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<DD>
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Allocation of storage failed.
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</DL>
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<A NAME="lbAG"> </A>
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<H2>ATTRIBUTES</H2>
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For an explanation of the terms used in this section, see
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<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
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<TABLE BORDER>
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<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>tempnam</B>()
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</TD><TD>Thread safety</TD><TD>MT-Safe env<BR></TD></TR>
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</TABLE>
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<A NAME="lbAH"> </A>
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<H2>CONFORMING TO</H2>
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SVr4, 4.3BSD, POSIX.1-2001.
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POSIX.1-2008 marks
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<B>tempnam</B>()
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as obsolete.
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<A NAME="lbAI"> </A>
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<H2>NOTES</H2>
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Although
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<B>tempnam</B>()
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generates names that are difficult to guess,
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it is nevertheless possible that between the time that
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<B>tempnam</B>()
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returns a pathname, and the time that the program opens it,
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another program might create that pathname using
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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2),
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or create it as a symbolic link.
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This can lead to security holes.
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To avoid such possibilities, use the
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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2)
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<B>O_EXCL</B>
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flag to open the pathname.
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Or better yet, use
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<B><A HREF="/cgi-bin/man/man2html?3+mkstemp">mkstemp</A></B>(3)
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or
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<B><A HREF="/cgi-bin/man/man2html?3+tmpfile">tmpfile</A></B>(3).
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<P>
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SUSv2 does not mention the use of
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<B>TMPDIR</B>;
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glibc will use it only
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when the program is not set-user-ID.
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On SVr4, the directory used under <B>d)</B> is
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<I>/tmp</I>
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(and this is what glibc does).
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<P>
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Because it dynamically allocates memory used to return the pathname,
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<B>tempnam</B>()
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is reentrant, and thus thread safe, unlike
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<B><A HREF="/cgi-bin/man/man2html?3+tmpnam">tmpnam</A></B>(3).
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<P>
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The
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<B>tempnam</B>()
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function generates a different string each time it is called,
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up to
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<B>TMP_MAX</B>
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(defined in
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<I><<A HREF="file:///usr/include/stdio.h">stdio.h</A>></I>)
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times.
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If it is called more than
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<B>TMP_MAX</B>
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times,
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the behavior is implementation defined.
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<P>
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<B>tempnam</B>()
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uses at most the first five bytes from
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<I>pfx</I>.
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<P>
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The glibc implementation of
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<B>tempnam</B>()
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fails with the error
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<B>EEXIST</B>
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upon failure to find a unique name.
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<A NAME="lbAJ"> </A>
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<H2>BUGS</H2>
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The precise meaning of "appropriate" is undefined;
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it is unspecified how accessibility of a directory is determined.
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<A NAME="lbAK"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?3+mkstemp">mkstemp</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+mktemp">mktemp</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+tmpfile">tmpfile</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+tmpnam">tmpnam</A></B>(3)
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<A NAME="lbAL"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="6"><A HREF="#lbAB">NAME</A><DD>
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<DT id="7"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="8"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="9"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="10"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="11"><A HREF="#lbAG">ATTRIBUTES</A><DD>
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<DT id="12"><A HREF="#lbAH">CONFORMING TO</A><DD>
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<DT id="13"><A HREF="#lbAI">NOTES</A><DD>
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<DT id="14"><A HREF="#lbAJ">BUGS</A><DD>
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<DT id="15"><A HREF="#lbAK">SEE ALSO</A><DD>
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<DT id="16"><A HREF="#lbAL">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:58 GMT, March 31, 2021
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</BODY>
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</HTML>
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