1FFS(3)                     Linux Programmer's Manual                    FFS(3)
2
3
4

NAME

6       ffs, ffsl, ffsll - find first bit set in a word
7

SYNOPSIS

9       #include <strings.h>
10
11       int ffs(int i);
12
13       #include <string.h>
14
15       int ffsl(long int i);
16
17       int ffsll(long long int i);
18
19   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
20
21       ffs():
22           Since glibc 2.12:
23               _SVID_SOURCE || _BSD_SOURCE || _POSIX_C_SOURCE >= 200809L ||
24               _XOPEN_SOURCE >= 700 ||
25           Before glibc 2.12:
26               none
27       ffsl(), ffsll():
28           _GNU_SOURCE
29

DESCRIPTION

31       The ffs() function returns the position of the  first  (least  signifi‐
32       cant)  bit  set in the word i.  The least significant bit is position 1
33       and the most significant position is, for example, 32 or 64.  The func‐
34       tions  ffsll()  and  ffsl()  do the same but take arguments of possibly
35       different size.
36

RETURN VALUE

38       These functions return the position of the first bit set, or  0  if  no
39       bits are set in i.
40

CONFORMING TO

42       ffs(): 4.3BSD, POSIX.1-2001.
43
44       The ffsl() and ffsll() functions are glibc extensions.
45

NOTES

47       BSD systems have a prototype in <string.h>.
48

SEE ALSO

50       memchr(3)
51

COLOPHON

53       This  page  is  part of release 3.53 of the Linux man-pages project.  A
54       description of the project, and information about reporting  bugs,  can
55       be found at http://www.kernel.org/doc/man-pages/.
56
57
58
59GNU                               2010-09-20                            FFS(3)
Impressum