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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek.
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.\"     from: @(#)ffs.3	8.2 (Berkeley) 4/19/94
.\"	$NetBSD: ffs.3,v 1.13 2010/04/28 07:47:09 jruoho Exp $
.\"
.Dd April 28, 2010
.Dt FFS 3
.Os
.Sh NAME
.Nm ffs
.Nd find first bit set in a bit string
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In strings.h
.Ft int
.Fn ffs "int value"
.Sh DESCRIPTION
The
.Fn ffs
function finds the first bit set in
.Fa value
and returns the index of that bit.
Bits are numbered starting from 1, starting at the right-most
bit.
A return value of 0 means that the argument was zero.
.Sh SEE ALSO
.Xr bitstring 3 ,
.Xr ffs32 3 ,
.Xr popcount 3
.Sh STANDARDS
The
.Fn ffs
function conforms to
.St -p1003.1-2001 .
.Sh HISTORY
The
.Fn ffs
function appeared in
.Bx 4.3 .
The prototype for it existed previously in the
.In string.h
header before it was moved to
.In strings.h
for
.Tn POSIX
compliance.