176 lines
3.9 KiB
HTML
176 lines
3.9 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 FFS</TITLE>
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</HEAD><BODY>
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<H1>FFS</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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ffs, ffsl, ffsll - find first bit set in a word
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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/strings.h">strings.h</A>></B>
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<B>int ffs(int </B><I>i</I><B>);</B>
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<B>#include <<A HREF="file:///usr/include/string.h">string.h</A>></B>
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<B>int ffsl(long int </B><I>i</I><B>);</B>
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<B>int ffsll(long long int </B><I>i</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>ffs</B>():
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<DL COMPACT><DT id="1"><DD>
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<DL COMPACT>
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<DT id="2">Since glibc 2.12:<DD>
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<BR> _XOPEN_SOURCE >= 700
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<BR> || ! (_POSIX_C_SOURCE >= 200809L)
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<BR> || /* Glibc since 2.19: */ _DEFAULT_SOURCE
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<BR> || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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<DT id="3">Before glibc 2.12:<DD>
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none
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</DL>
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</DL>
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<P>
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<B>ffsl</B>(),
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<B>ffsll</B>():
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<DL COMPACT><DT id="4"><DD>
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<DL COMPACT>
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<DT id="5">Since glibc 2.27:<DD>
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<BR> _DEFAULT_SOURCE
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<DT id="6">Before glibc 2.27:<DD>
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<BR> _GNU_SOURCE
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</DL>
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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The
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<B>ffs</B>()
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function returns the position of the first
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(least significant) bit set in the word <I>i</I>.
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The least significant bit is position 1 and the
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most significant position is, for example, 32 or 64.
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The functions
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<B>ffsll</B>()
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and
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<B>ffsl</B>()
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do the same but take
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arguments of possibly different size.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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These functions return the position of the first bit set,
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or 0 if no bits are set in
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<I>i</I>.
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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>ffs</B>(),
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<B>ffsl</B>(),
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<B>ffsll</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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<B>ffs</B>():
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POSIX.1-2001, POSIX.1-2008, 4.3BSD.
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<P>
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The
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<B>ffsl</B>()
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and
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<B>ffsll</B>()
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functions are glibc extensions.
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<A NAME="lbAH"> </A>
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<H2>NOTES</H2>
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BSD systems have a prototype in
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<I><<A HREF="file:///usr/include/string.h">string.h</A>></I>.
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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+memchr">memchr</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">ATTRIBUTES</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">NOTES</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: 00:05:42 GMT, March 31, 2021
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</BODY>
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</HTML>
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