ffs(3)

NAME

ffs, ffsl, fls, flsl - find first or last bit set in a bit

string

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <strings.h>
int
ffs(int value);
int
ffsl(long value);
int
fls(int value);
int
flsl(long value);

DESCRIPTION

The ffs() and ffsl() functions find the first bit set in

value and return
the index of that bit.

The fls() and flsl() functions find the last bit set in

value and return
the index of that bit.

Bits are numbered starting from 1, starting at the right

most (least significant) bit. A return value of zero from any of these

functions means
that the argument was zero.

SEE ALSO

bitstring(3)

HISTORY

The ffs() function appeared in 4.3BSD. Its prototype exist

ed previously
in #include <string.h>
before it was moved to #include <strings.h> for compliance.

The ffsl(), fls() and flsl() functions appeared in FreeBSD

5.3.

BSD January 13, 2004

BSD