|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
FFS(3) Linux Programmer's Manual FFS(3)
ffs, ffsl, ffsll - find first bit set in a word
#include <strings.h>
int ffs(int i);
#include <string.h>
int ffsl(long int i);
int ffsll(long long int i);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
ffs():
Since glibc 2.12:
_XOPEN_SOURCE >= 700
|| ! (_POSIX_C_SOURCE >= 200809L)
|| /* Glibc since 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
_SVID_SOURCE
Before glibc 2.12:
none
ffsl(), ffsll():
_GNU_SOURCE
The ffs() function returns the position of the first (least
significant) bit set in the word i. The least significant bit is
position 1 and the most significant position is, for example, 32 or
64. The functions ffsll() and ffsl() do the same but take arguments
of possibly different size.
These functions return the position of the first bit set, or 0 if no
bits are set in i.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├───────────────────────┼───────────────┼─────────┤
│ffs(), ffsl(), ffsll() │ Thread safety │ MT-Safe │
└───────────────────────┴───────────────┴─────────┘
ffs(): POSIX.1-2001, POSIX.1-2008, 4.3BSD.
The ffsl() and ffsll() functions are glibc extensions.
BSD systems have a prototype in <string.h>.
memchr(3)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
GNU 2016-10-08 FFS(3)
Pages that refer to this page: memchr(3), signal-safety(7)