FFS
Section: Linux Programmer's Manual (3)
Updated: 2014-04-14
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NAME
ffs, ffsl, ffsll - find first bit set in a word
SYNOPSIS
#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
DESCRIPTION
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.
RETURN VALUE
These functions return the position of the first bit set,
or 0 if no bits are set in
i.
ATTRIBUTES
Multithreading (see pthreads(7))
The
ffs(),
ffsl(),
and
ffsll()
functions are thread-safe.
CONFORMING TO
ffs():
4.3BSD, POSIX.1-2001.
The
ffsl()
and
ffsll()
functions are glibc extensions.
NOTES
BSD systems have a prototype in
<string.h>.
SEE ALSO
memchr(3)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ATTRIBUTES
-
- Multithreading (see pthreads(7))
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
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Time: 02:55:12 GMT, September 18, 2014