Provided by: manpages-dev_5.05-1_all bug

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 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).

       ┌───────────────────────┬───────────────┬─────────┐
       │InterfaceAttributeValue   │
       ├───────────────────────┼───────────────┼─────────┤
       │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.

NOTES

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

SEE ALSO

       memchr(3)

COLOPHON

       This page is part of release 5.05 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/.