FFS(3) Linux Programmer s Manual FFS(3)

NAME ffs - 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 signifi- cant) bit set in the word i. The least significant bit is position 1 and the most significant position e.g. 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 4.3BSD, POSIX.1-2001.

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

GNU 2003-08-05 FFS(3)