ffs (3)
Leading comments
Copyright 1993 David Metcalfe (david@prism.demon.co.uk) %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Sin...
NAME
ffs, ffsl, ffsll - find first bit set in a wordSYNOPSIS
#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:
- _SVID_SOURCE || _BSD_SOURCE || _POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700 ||
- Before glibc 2.12:
- none
ffsl(), ffsll():
- _GNU_SOURCE
DESCRIPTION
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.RETURN VALUE
These functions return the position of the first bit set, or 0 if no bits are set in i.ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).| Interface | Attribute | Value |
| ffs(), ffsl(), ffsll() | Thread safety | MT-Safe |
CONFORMING TO
ffs(): POSIX.1-2001, POSIX.1-2008, 4.3BSD.The ffsl() and ffsll() functions are glibc extensions.