FLS(9) Basic C Library Functions FLS(9)NAME
fls - find last set bit in word
SYNOPSIS
int fls(int x);
ARGUMENTS
x
the word to search
DESCRIPTION
This is defined in a similar way as the libc and compiler builtin ffs, but returns the position of the most significant set bit.
fls(value) returns 0 if value is 0 or the position of the last set bit if value is nonzero. The last (most significant) bit is at position
32.
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 FLS(9)
Check Out this Related Man Page
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:
_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.
CONFORMING TO
ffs(): 4.3BSD, POSIX.1-2001.
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 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 2010-09-20 FFS(3)