NAME
ffs, ffsl,
ffsll, fls,
flsl, flsll —
find first or last bit set in a bit
string
LIBRARY
library “libc”
SYNOPSIS
#include
<strings.h>
int
ffs(int
value);
int
ffsl(long
value);
int
ffsll(long
long value);
int
fls(int
value);
int
flsl(long
value);
int
flsll(long
long value);
DESCRIPTION
Theffs(),
ffsl()
and
ffsll()
functions find the first (least significant) bit set in
value and return the index of that bit.
The
fls(),
flsl()
and
flsll()
functions find the last (most significant) bit set in
value and return the index of that bit.
Bits are numbered starting at 1, the least significant bit. A return value of zero from any of these functions means that the argument was zero.
SEE ALSO
HISTORY
The ffs() function appeared in
4.3BSD. Its prototype existed previously in
<string.h> before it was
moved to <strings.h> for
IEEE Std 1003.1-2001 (“POSIX.1”)
compliance.
The ffsl(), fls()
and flsl() functions appeared in
FreeBSD 5.3. The ffsll() and
flsll() functions appeared in
FreeBSD 7.1.