osx man page for fls

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

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

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <strings.h>

     int
     ffs(int i);

     int
     ffsl(long i);

     int
     fls(int i);

     int
     flsl(long i);

DESCRIPTION
     The ffs() and ffsl() functions find the first bit set in i and return the index of that bit.

     The fls() and flsl() functions find the last bit set in i and return the index of that bit.

     Bits are numbered starting from 1, starting at the right-most (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.

BSD
								 January 13, 2004							       BSD