2004-11-03 13:51:07 +00:00
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.\" 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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2007-04-12 22:42:49 +00:00
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.\"
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2004-11-03 13:51:07 +00:00
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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.\" manual page may be incorrect or out-of-date.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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2007-04-12 22:42:49 +00:00
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.\"
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2004-11-03 13:51:07 +00:00
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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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2007-04-12 22:42:49 +00:00
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.\"
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_exit.2, brk.2, capget.2, chdir.2, chmod.2, chown.2, chroot.2, getdtablesize.2, gethostname.2, getpagesize.2, getsid.2, killpg.2, mknod.2, mknodat.2, poll.2, posix_fadvise.2, pread.2, readlink.2, setpgid.2, setreuid.2, sigaltstack.2, stat.2, symlink.2, sync.2, truncate.2, vfork.2, wait.2, wait4.2, a64l.3, abs.3, acos.3, acosh.3, asin.3, asinh.3, atan.3, atan2.3, atoi.3, cbrt.3, ceil.3, copysign.3, cosh.3, dirfd.3, div.3, ecvt.3, erf.3, erfc.3, exp.3, exp2.3, fabs.3, fdim.3, ffs.3, floor.3, fma.3, fmax.3, fmin.3, fmod.3, fpclassify.3, frexp.3, ftw.3, fwide.3, gcvt.3, getcwd.3, getdate.3, getgrent.3, gethostid.3, getpass.3, getpwent.3, getsubopt.3, getw.3, hypot.3, ilogb.3, index.3, isalpha.3, isgreater.3, iswblank.3, j0.3, ldexp.3, lockf.3, log.3, log10.3, log1p.3, logb.3, lrint.3, lround.3, mkstemp.3, mktemp.3, modf.3, mq_receive.3, mq_send.3, nan.3, nextafter.3, posix_fallocate.3, posix_memalign.3, printf.3, qecvt.3, random.3, realpath.3, remainder.3, remquo.3, rint.3, round.3, scalb.3, scalbln.3, scanf.3, siginterrupt.3, signbit.3, sigset.3, sinh.3, sqrt.3, strcasecmp.3, strcat.3, strchr.3, strcmp.3, strcoll.3, strcpy.3, strfry.3, strpbrk.3, strsep.3, strspn.3, strstr.3, strtod.3, strtok.3, strtol.3, strtoul.3, strxfrm.3, tanh.3, tgamma.3, trunc.3, ttyslot.3, ualarm.3, usleep.3, wprintf.3, armscii-8.7, cp1251.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-3.7, iso_8859-5.7, iso_8859-6.7, iso_8859-8.7, koi8-u.7: tstamp
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-09-19 17:19:13 +00:00
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.TH FFS 3 2010-09-20 "GNU" "Linux Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.SH NAME
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2007-07-08 14:26:39 +00:00
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ffs, ffsl, ffsll \- find first bit set in a word
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2004-11-03 13:51:07 +00:00
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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 #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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2010-09-18 03:30:36 +00:00
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.PD 0
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.ad l
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.sp
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.BR ffs ():
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.RS 4
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.TP 4
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Since glibc 2.12:
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_SVID_SOURCE || _BSD_SOURCE ||
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_POSIX_C_SOURCE\ >=\ 200809L || _XOPEN_SOURCE\ >=\ 700 ||
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.TP
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Before glibc 2.12:
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none
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.RE
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.PP
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.BR ffsl (),
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.BR ffsll ():
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2010-09-19 04:58:22 +00:00
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.RS 4
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2010-09-18 03:30:36 +00:00
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_GNU_SOURCE
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2010-09-19 04:58:22 +00:00
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.RE
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2010-09-18 03:30:36 +00:00
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.ad
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.PD
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2004-11-03 13:51:07 +00:00
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.SH DESCRIPTION
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2007-05-12 09:06:04 +00:00
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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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2004-11-03 13:51:07 +00:00
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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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2007-06-08 11:56:22 +00:00
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most significant position is, for example, 32 or 64.
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2007-05-12 09:06:04 +00:00
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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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2004-11-03 13:51:07 +00:00
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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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2006-05-17 21:33:53 +00:00
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or 0 if no bits are set in
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.IR i .
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2004-11-03 13:51:07 +00:00
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.SH "CONFORMING TO"
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2010-09-11 04:33:13 +00:00
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.BR ffs ():
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4.3BSD, POSIX.1-2001.
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2010-09-11 04:33:34 +00:00
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2009-08-27 09:18:19 +00:00
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The
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.BR ffsl ()
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and
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.BR ffsll ()
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2010-09-11 04:33:34 +00:00
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functions are glibc extensions.
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2004-11-03 13:51:07 +00:00
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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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2007-01-28 20:00:24 +00:00
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.SH "SEE ALSO"
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getresuid.2, intro.2, mremap.2, open.2, poll.2, posix_fadvise.2, pread.2, remap_file_pages.2, setresuid.2, signal.2, splice.2, sync_file_range.2, tee.2, vmsplice.2, INFINITY.3, asprintf.3, assert_perror.3, basename.3, bsd_signal.3, canonicalize_file_name.3, clog10.3, crypt.3, dl_iterate_phdr.3, dlopen.3, dprintf.3, encrypt.3, exp10.3, fcloseall.3, fenv.3, ffs.3, fmemopen.3, fopencookie.3, ftw.3, getdate.3, getline.3, getloadavg.3, getopt.3, getsubopt.3, getutent.3, grantpt.3, hsearch.3, intro.3, lseek64.3, memmem.3, mempcpy.3, mq_receive.3, mq_send.3, posix_fallocate.3, pow10.3, program_invocation_name.3, ptsname.3, putgrent.3, readdir.3, sigset.3, sincos.3, stpcpy.3, stpncpy.3, strchr.3, strfry.3, strnlen.3, strptime.3, strsignal.3, strstr.3, strverscmp.3, swab.3, sysv_signal.3, tsearch.3, unlocked_stdio.3, unlockpt.3, wcpcpy.3, wcpncpy.3, wcsdup.3, wcwidth.3: SEE ALSO: Remove redundant reference to feature_test_macros(7)
Reported-by: Florian Lehmann <flo.lehmann@googlemail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-10-31 05:05:22 +00:00
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.BR memchr (3)
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