| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES | SEE ALSO | COLOPHON | The Linux Programming Interface |
FFS(3) Linux Programmer's Manual FFS(3)
ffs, ffsl, ffsll - find first bit set in a word
#include <strings.h>
int ffs(int i);
#include <string.h>
int ffsl(long int i);
int ffsll(long long int i);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
ffs():
Since glibc 2.12:
_SVID_SOURCE || _BSD_SOURCE || _POSIX_C_SOURCE >= 200809L ||
_XOPEN_SOURCE >= 700 ||
Before glibc 2.12:
none
ffsl(), ffsll():
_GNU_SOURCE
The ffs() function returns the position of the first (least
significant) 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 functions ffsll() and ffsl() do the same but take arguments
of possibly different size.
These functions return the position of the first bit set, or 0 if no
bits are set in i.
ffs(): 4.3BSD, POSIX.1-2001.
The ffsl() and ffsll() functions are glibc extensions.
BSD systems have a prototype in <string.h>.
memchr(3)
This page is part of release 3.51 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 2010-09-20 FFS(3)
HTML rendering created 2013-05-17 by Michael Kerrisk, author of The Linux Programming Interface, maintainer of the Linux man-pages project
Hosting by jambit GmbH