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 signifi- cant) 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 func- tions 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.


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

SEE ALSO memchr(3), feature_test_macros(7)

COLOPHON This page is part of release 3.22 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 2009-04-21 FFS(3)