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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  signifi-
       cant)  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 func-
       tions  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 3.53 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)