291 lines
6.3 KiB
HTML
291 lines
6.3 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 SETBUF</TITLE>
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</HEAD><BODY>
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<H1>SETBUF</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2019-03-06<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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setbuf, setbuffer, setlinebuf, setvbuf - stream buffering operations
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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>void setbuf(FILE *</B><I>stream</I><B>, char *</B><I>buf</I><B>);</B>
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<B>void setbuffer(FILE *</B><I>stream</I><B>, char *</B><I>buf</I><B>, size_t </B><I>size</I><B>);</B>
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<B>void setlinebuf(FILE *</B><I>stream</I><B>);</B>
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<B>int setvbuf(FILE *</B><I>stream</I><B>, char *</B><I>buf</I><B>, int </B><I>mode</I><B>, size_t </B><I>size</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>setbuffer</B>(),
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<B>setlinebuf</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
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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The three types of buffering available are unbuffered, block buffered, and
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line buffered.
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When an output stream is unbuffered, information appears on
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the destination file or terminal as soon as written; when it is block
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buffered many characters are saved up and written as a block; when it is
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line buffered characters are saved up until a newline is output or input is
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read from any stream attached to a terminal device (typically <I>stdin</I>).
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The function
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<B><A HREF="/cgi-bin/man/man2html?3+fflush">fflush</A></B>(3)
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may be used to force the block out early.
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(See
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<B><A HREF="/cgi-bin/man/man2html?3+fclose">fclose</A></B>(3).)
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<P>
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Normally all files are block buffered.
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If a stream refers to a terminal (as
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<I>stdout</I>
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normally does), it is line buffered.
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The standard error stream
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<I>stderr</I>
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is always unbuffered by default.
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<P>
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The
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<B>setvbuf</B>()
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function may be used on any open stream to change its buffer.
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The
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<I>mode</I>
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argument must be one of the following three macros:
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<DL COMPACT><DT id="1"><DD>
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<DL COMPACT>
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<DT id="2"><B>_IONBF</B>
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<DD>
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unbuffered
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<DT id="3"><B>_IOLBF</B>
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<DD>
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line buffered
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<DT id="4"><B>_IOFBF</B>
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<DD>
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fully buffered
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</DL>
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</DL>
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<P>
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Except for unbuffered files, the
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<I>buf</I>
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argument should point to a buffer at least
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<I>size</I>
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bytes long; this buffer will be used instead of the current buffer.
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If the argument
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<I>buf</I>
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is NULL,
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only the mode is affected; a new buffer will be allocated on the next read
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or write operation.
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The
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<B>setvbuf</B>()
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function may be used only after opening a stream and before any other
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operations have been performed on it.
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<P>
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The other three calls are, in effect, simply aliases for calls to
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<B>setvbuf</B>().
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The
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<B>setbuf</B>()
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function is exactly equivalent to the call
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<P>
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setvbuf(stream, buf, buf ? _IOFBF : _IONBF, BUFSIZ);
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<P>
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The
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<B>setbuffer</B>()
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function is the same, except that the size of the buffer is up to the
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caller, rather than being determined by the default
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<B>BUFSIZ</B>.
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The
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<B>setlinebuf</B>()
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function is exactly equivalent to the call:
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<P>
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setvbuf(stream, NULL, _IOLBF, 0);
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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The function
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<B>setvbuf</B>()
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returns 0 on success.
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It returns nonzero on failure
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(<I>mode</I>
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is invalid or the request cannot be honored).
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It may set
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<I>errno</I>
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on failure.
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<P>
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The other functions do not return a value.
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<A NAME="lbAF"> </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>setbuf</B>(),
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<B>setbuffer</B>(),
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<BR>
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<B>setlinebuf</B>(),
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<B>setvbuf</B>()
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</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
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</TABLE>
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<A NAME="lbAG"> </A>
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<H2>CONFORMING TO</H2>
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The
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<B>setbuf</B>()
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and
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<B>setvbuf</B>()
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functions conform to C89 and C99.
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<A NAME="lbAH"> </A>
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<H2>BUGS</H2>
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<P>
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You must make sure that the space that
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<I>buf</I>
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points to still exists by the time
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<I>stream</I>
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is closed, which also happens at program termination.
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For example, the following is invalid:
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<P>
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#include <<A HREF="file:///usr/include/stdio.h">stdio.h</A>>
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<P>
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int
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main(void)
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{
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<BR> char buf[BUFSIZ];
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<BR> setbuf(stdin, buf);
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<BR> printf("Hello, world!\n");
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<BR> return 0;
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}
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<A NAME="lbAI"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+stdbuf">stdbuf</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?3+fclose">fclose</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+fflush">fflush</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+fopen">fopen</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+fread">fread</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+malloc">malloc</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+printf">printf</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+puts">puts</A></B>(3)
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<A NAME="lbAJ"> </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="5"><A HREF="#lbAB">NAME</A><DD>
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<DT id="6"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="7"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="8"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="9"><A HREF="#lbAF">ATTRIBUTES</A><DD>
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<DT id="10"><A HREF="#lbAG">CONFORMING TO</A><DD>
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<DT id="11"><A HREF="#lbAH">BUGS</A><DD>
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<DT id="12"><A HREF="#lbAI">SEE ALSO</A><DD>
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<DT id="13"><A HREF="#lbAJ">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: 00:05:56 GMT, March 31, 2021
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</BODY>
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</HTML>
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