ffs(9) centos man page | unix.com

FFS(9)							     Basic C Library Functions							    FFS(9)

NAME
       ffs - find first set bit in word

SYNOPSIS
       int ffs(int x);

ARGUMENTS
       x
	   the word to search

DESCRIPTION
       This is defined the same way as the libc and compiler builtin ffs routines, therefore differs in spirit from the other bitops.

       ffs(value) returns 0 if value is 0 or the position of the first set bit if value is nonzero. The first (least significant) bit is at
       position 1.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014								    FFS(9)