man:ffsl
FFS(3) Linux Programmer's Manual FFS(3)
NAME
ffs, ffsl, ffsll - find first bit set in a word
SYNOPSIS
#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(): Since glibc 2.27: _DEFAULT_SOURCE Before glibc 2.27: _GNU_SOURCE
DESCRIPTION
The ffs() function returns the position of the first (least signifi- cant) 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 func- tions 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).
allbox; lbw22 lb lb l l l. Interface Attribute Value T{ ffs(), ffsl(), ffsll() T} Thread safety MT-Safe
CONFORMING TO
ffs(): POSIX.1-2001, POSIX.1-2008, 4.3BSD.
The ffsl() and ffsll() functions are glibc extensions.
NOTES
BSD systems have a prototype in <string.h>.
SEE ALSO
memchr(3)
COLOPHON
This page is part of release 4.16 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 2017-09-15 FFS(3)
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