1.\" Copyright (c) 1990, 1991, 1993
2.\" The Regents of the University of California. All rights reserved.
3.\"
4.\" This code is derived from software contributed to Berkeley by
5.\" Chris Torek.
6.\" Redistribution and use in source and binary forms, with or without
7.\" modification, are permitted provided that the following conditions
8.\" are met:
9.\" 1. Redistributions of source code must retain the above copyright
10.\" notice, this list of conditions and the following disclaimer.
11.\" 2. Redistributions in binary form must reproduce the above copyright
12.\" notice, this list of conditions and the following disclaimer in the
13.\" documentation and/or other materials provided with the distribution.
14.\" 3. All advertising materials mentioning features or use of this software
15.\" must display the following acknowledgement:
16.\" This product includes software developed by the University of
17.\" California, Berkeley and its contributors.
18.\" 4. Neither the name of the University nor the names of its contributors
19.\" may be used to endorse or promote products derived from this software
20.\" without specific prior written permission.
21.\"
22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32.\" SUCH DAMAGE.
33.\"
34.\" @(#)ffs.3 8.2 (Berkeley) 4/19/94
35.\" $FreeBSD: head/lib/libc/string/ffs.3 124483 2004-01-13 16:05:47Z des $
36.\"
37.Dd April 19, 1994
38.Dt FFS 3
39.Os
40.Sh NAME
41.Nm ffs ,
42.Nm ffsl ,
43.Nm fls ,
44.Nm flsl
45.Nd find first or last bit set in a bit string
46.Sh LIBRARY
47.Lb libc
48.Sh SYNOPSIS
49.In strings.h
50.Ft int
51.Fn ffs "int value"
52.Ft int
53.Fn ffsl "long value"
54.Ft int
55.Fn fls "int value"
56.Ft int
57.Fn flsl "long value"
58.Sh DESCRIPTION
59The
60.Fn ffs
61and
62.Fn ffsl
63functions find the first bit set in
64.Fa value
65and return the index of that bit.
66.Pp
67The
68.Fn fls
69and
70.Fn flsl
71functions find the last bit set in
72.Fa value
73and return the index of that bit.
74.Pp
75Bits are numbered starting from 1, starting at the right-most
76(least significant) bit.
77A return value of zero from any of these functions means that the
78argument was zero.
79.Sh SEE ALSO
80.Xr bitstring 3
81.Sh HISTORY
82The
83.Fn ffs
84function appeared in
85.Bx 4.3 .
86Its prototype existed previously in
87.In string.h
88before it was moved to
89.In strings.h
90for
91.St -p1003.1-2001
92compliance.
93.Pp
94The
95.Fn ffsl ,
96.Fn fls
97and
98.Fn flsl
99functions appeared in
100.Fx 5.3 .
2.\" The Regents of the University of California. All rights reserved.
3.\"
4.\" This code is derived from software contributed to Berkeley by
5.\" Chris Torek.
6.\" Redistribution and use in source and binary forms, with or without
7.\" modification, are permitted provided that the following conditions
8.\" are met:
9.\" 1. Redistributions of source code must retain the above copyright
10.\" notice, this list of conditions and the following disclaimer.
11.\" 2. Redistributions in binary form must reproduce the above copyright
12.\" notice, this list of conditions and the following disclaimer in the
13.\" documentation and/or other materials provided with the distribution.
14.\" 3. All advertising materials mentioning features or use of this software
15.\" must display the following acknowledgement:
16.\" This product includes software developed by the University of
17.\" California, Berkeley and its contributors.
18.\" 4. Neither the name of the University nor the names of its contributors
19.\" may be used to endorse or promote products derived from this software
20.\" without specific prior written permission.
21.\"
22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32.\" SUCH DAMAGE.
33.\"
34.\" @(#)ffs.3 8.2 (Berkeley) 4/19/94
35.\" $FreeBSD: head/lib/libc/string/ffs.3 124483 2004-01-13 16:05:47Z des $
36.\"
37.Dd April 19, 1994
38.Dt FFS 3
39.Os
40.Sh NAME
41.Nm ffs ,
42.Nm ffsl ,
43.Nm fls ,
44.Nm flsl
45.Nd find first or last bit set in a bit string
46.Sh LIBRARY
47.Lb libc
48.Sh SYNOPSIS
49.In strings.h
50.Ft int
51.Fn ffs "int value"
52.Ft int
53.Fn ffsl "long value"
54.Ft int
55.Fn fls "int value"
56.Ft int
57.Fn flsl "long value"
58.Sh DESCRIPTION
59The
60.Fn ffs
61and
62.Fn ffsl
63functions find the first bit set in
64.Fa value
65and return the index of that bit.
66.Pp
67The
68.Fn fls
69and
70.Fn flsl
71functions find the last bit set in
72.Fa value
73and return the index of that bit.
74.Pp
75Bits are numbered starting from 1, starting at the right-most
76(least significant) bit.
77A return value of zero from any of these functions means that the
78argument was zero.
79.Sh SEE ALSO
80.Xr bitstring 3
81.Sh HISTORY
82The
83.Fn ffs
84function appeared in
85.Bx 4.3 .
86Its prototype existed previously in
87.In string.h
88before it was moved to
89.In strings.h
90for
91.St -p1003.1-2001
92compliance.
93.Pp
94The
95.Fn ffsl ,
96.Fn fls
97and
98.Fn flsl
99functions appeared in
100.Fx 5.3 .