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);

       #define _GNU_SOURCE
       #include <string.h>

       int ffsl(long int i);

       int ffsll(long long int i);

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() are glibc extensions.

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

SEE ALSO
       memchr(3), feature_test_macros(7)

COLOPHON
       This  page  is  part of release 3.25 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                                                        2009-08-27                                                     FFS(3)