13.1 ffs—find first bit set in a word ¶

Synopsis

#include <strings.h>
int ffs(int word);

Description

ffs returns the first bit set in a word.

Returns
ffs returns 0 if c is 0, 1 if c is odd, 2 if c is a multiple of 2, etc.

Portability
ffs is not ANSI C.

No supporting OS subroutines are required.