mirror of https://github.com/mkerrisk/man-pages
73 lines
2.3 KiB
Groff
73 lines
2.3 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified Sat Jul 24 19:39:35 1993 by Rik Faith (faith@cs.unc.edu)
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.\"
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.\" Modified 2003 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
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.\"
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.TH FFS 3 2003-08-05 "GNU" "Linux Programmer's Manual"
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.SH NAME
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ffs, ffsl, ffsll \- find first bit set in a word
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.SH SYNOPSIS
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.nf
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.B #include <strings.h>
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.sp
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.BI "int ffs(int " i );
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.sp
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.B #define _GNU_SOURCE
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.br
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.B #include <string.h>
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.sp
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.BI "int ffsl(long int " i );
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.sp
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.BI "int ffsll(long long int " i );
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.fi
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.SH DESCRIPTION
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The
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.BR ffs ()
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function returns the position of the first
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(least significant) bit set in the word \fIi\fP.
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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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.BR
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The functions
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.BR ffsll ()
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and
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.BR ffsl ()
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do the same but take
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arguments of possibly different size.
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.SH "RETURN VALUE"
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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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.IR i .
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.SH "CONFORMING TO"
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4.3BSD, POSIX.1-2001.
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.SH NOTES
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BSD systems have a prototype in
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.IR <string.h> .
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.SH "SEE ALSO"
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.BR feature_test_macros (7)
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