fls(3) [freebsd man page]

FFS(3)							   BSD Library Functions Manual 						    FFS(3)

NAME

     ffs, ffsl, ffsll, fls, flsl, flsll -- find first or last bit set in a bit string

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <strings.h>

     int
     ffs(int value);

     int
     ffsl(long value);

     int
     ffsll(long long value);

     int
     fls(int value);

     int
     flsl(long value);

     int
     flsll(long long value);

DESCRIPTION

     The ffs(), ffsl() and ffsll() functions find the first (least significant) bit set in value and return the index of that bit.

     The fls(), flsl() and flsll() functions find the last (most significant) bit set in value and return the index of that bit.

     Bits are numbered starting at 1, the least significant bit.  A return value of zero from any of these functions means that the argument was
     zero.

SEE ALSO

     bitstring(3)

HISTORY

     The ffs() function appeared in 4.3BSD.  Its prototype existed previously in <string.h> before it was moved to <strings.h> for IEEE Std
     1003.1-2001 (``POSIX.1'') compliance.

     The ffsl(), fls() and flsl() functions appeared in FreeBSD 5.3.  The ffsll() and flsll() functions appeared in FreeBSD 7.1.

BSD
								September 29, 2012							       BSD

FFS(3)							     Linux Programmer's Manual							    FFS(3)

NAME

       ffs, ffsl, ffsll - find first bit set in a word

SYNOPSIS

       #include <strings.h>

       int ffs(int i);

       #include <string.h>

       int ffsl(long int i);

       int ffsll(long long int i);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       ffs():
	   Since glibc 2.12:
	       _SVID_SOURCE || _BSD_SOURCE || _POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700 ||
	   Before glibc 2.12:
	       none
       ffsl(), ffsll():
	   _GNU_SOURCE

DESCRIPTION

       The  ffs()  function  returns the position of the first (least significant) bit set in the word i.  The least significant bit is position 1
       and the most significant position is, for example, 32 or 64.  The functions ffsll() and ffsl() do the same but take arguments  of  possibly
       different size.

RETURN VALUE

       These functions return the position of the first bit set, or 0 if no bits are set in i.

CONFORMING TO

       ffs(): 4.3BSD, POSIX.1-2001.

       The ffsl() and ffsll() functions are glibc extensions.

NOTES

       BSD systems have a prototype in <string.h>.

SEE ALSO

       memchr(3)

COLOPHON

       This  page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

GNU
								    2010-09-20								    FFS(3)