284 lines
6.0 KiB
HTML
284 lines
6.0 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 LGAMMA</TITLE>
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</HEAD><BODY>
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<H1>LGAMMA</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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lgamma, lgammaf, lgammal, lgamma_r, lgammaf_r, lgammal_r, signgam -
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log gamma function
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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/math.h">math.h</A>></B>
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<B>double lgamma(double </B><I>x</I><B>);</B>
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<B>float lgammaf(float </B><I>x</I><B>);</B>
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<B>long double lgammal(long double </B><I>x</I><B>);</B>
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<B>double lgamma_r(double </B><I>x</I><B>, int *</B><I>signp</I><B>);</B>
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<B>float lgammaf_r(float </B><I>x</I><B>, int *</B><I>signp</I><B>);</B>
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<B>long double lgammal_r(long double </B><I>x</I><B>, int *</B><I>signp</I><B>);</B>
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<B>extern int </B><I>signgam</I><B>;</B>
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</PRE>
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<P>
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Link with <I>-lm</I>.
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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>lgamma</B>():
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<DL COMPACT><DT id="1"><DD>
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_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE
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<BR> || /* Since glibc 2.19: */ _DEFAULT_SOURCE
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<BR> || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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</DL>
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<BR>
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<B>lgammaf</B>(),
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<B>lgammal</B>():
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<DL COMPACT><DT id="2"><DD>
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_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
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<BR> || /* Since glibc 2.19: */ _DEFAULT_SOURCE
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<BR> || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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</DL>
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<B>lgamma_r</B>(),
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<B>lgammaf_r</B>(),
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<B>lgammal_r</B>():
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<DL COMPACT><DT id="3"><DD>
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/* Since glibc 2.19: */ _DEFAULT_SOURCE
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<BR> || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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</DL>
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<I>signgam</I>:
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<DL COMPACT><DT id="4"><DD>
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_XOPEN_SOURCE
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<BR> || /* Since glibc 2.19: */ _DEFAULT_SOURCE
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<BR> || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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For the definition of the Gamma function, see
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<B><A HREF="/cgi-bin/man/man2html?3+tgamma">tgamma</A></B>(3).
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<P>
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The
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<B>lgamma</B>(),
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<B>lgammaf</B>(),
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and
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<B>lgammal</B>()
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functions return the natural logarithm of
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the absolute value of the Gamma function.
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The sign of the Gamma function is returned in the
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external integer
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<I>signgam</I>
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declared in
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<I><<A HREF="file:///usr/include/math.h">math.h</A>></I>.
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It is 1 when the Gamma function is positive or zero, -1
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when it is negative.
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<P>
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Since using a constant location
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<I>signgam</I>
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is not thread-safe, the functions
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<B>lgamma_r</B>(),
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<B>lgammaf_r</B>(),
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and
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<B>lgammal_r</B>()
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have been introduced; they return the sign via the argument
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<I>signp</I>.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success, these functions return the natural logarithm of Gamma(x).
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<P>
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If
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<I>x</I>
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is a NaN, a NaN is returned.
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<P>
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If
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<I>x</I>
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is 1 or 2, +0 is returned.
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<P>
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If
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<I>x</I>
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is positive infinity or negative infinity,
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positive infinity is returned.
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<P>
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If
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<I>x</I>
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is a nonpositive integer,
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a pole error occurs,
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and the functions return
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+<B>HUGE_VAL</B>,
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+<B>HUGE_VALF</B>,
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or
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+<B>HUGE_VALL</B>,
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respectively.
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<P>
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If the result overflows,
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a range error occurs,
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and the functions return
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<B>HUGE_VAL</B>,
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<B>HUGE_VALF</B>,
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or
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<B>HUGE_VALL</B>,
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respectively, with the correct mathematical sign.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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See
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<B><A HREF="/cgi-bin/man/man2html?7+math_error">math_error</A></B>(7)
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for information on how to determine whether an error has occurred
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when calling these functions.
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<P>
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The following errors can occur:
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<DL COMPACT>
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<DT id="5">Pole error: <I>x</I> is a nonpositive integer<DD>
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<I>errno</I>
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is set to
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<B>ERANGE</B>
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(but see BUGS).
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A divide-by-zero floating-point exception
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(<B>FE_DIVBYZERO</B>)
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is raised.
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<DT id="6">Range error: result overflow<DD>
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<I>errno</I>
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is set to
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<B>ERANGE</B>.
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An overflow floating-point exception
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(<B>FE_OVERFLOW</B>)
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is raised.
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</DL>
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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>lgamma</B>()
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functions are specified in C99, POSIX.1-2001, and POSIX.1-2008.
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<I>signgam</I>
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is specified in POSIX.1-2001 and POSIX.1-2008, but not in C99.
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The
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<B>lgamma_r</B>()
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functions are nonstandard, but present on several other systems.
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<A NAME="lbAH"> </A>
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<H2>BUGS</H2>
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In glibc 2.9 and earlier,
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when a pole error occurs,
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<I>errno</I>
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is set to
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<B>EDOM</B>;
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instead of the POSIX-mandated
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<B>ERANGE</B>.
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Since version 2.10, glibc does the right thing.
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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?3+tgamma">tgamma</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="7"><A HREF="#lbAB">NAME</A><DD>
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<DT id="8"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="9"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="10"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="11"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="12"><A HREF="#lbAG">CONFORMING TO</A><DD>
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<DT id="13"><A HREF="#lbAH">BUGS</A><DD>
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<DT id="14"><A HREF="#lbAI">SEE ALSO</A><DD>
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<DT id="15"><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: 00:05:47 GMT, March 31, 2021
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