dwww Home | Manual pages | Find package

ffs(3)                     Library Functions Manual                     ffs(3)

NAME
       ffs, ffsl, ffsll - find first bit set in a word

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #include <strings.h>

       int ffs(int i);

       #include <string.h>

       int ffsl(long i);
       int ffsll(long long 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 >= 2.19: */ _DEFAULT_SOURCE
                   || /* glibc <= 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  at-
       tributes(7).

       ┌────────────────────────────────────────────┬───────────────┬─────────┐
       │InterfaceAttributeValue   │
       ├────────────────────────────────────────────┼───────────────┼─────────┤
       │ffs(), ffsl(), ffsll()                      │ Thread safety │ MT-Safe │
       └────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS
       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)

Linux man-pages 6.03              2023-02-05                            ffs(3)

Generated by dwww version 1.15 on Sun Jun 16 12:03:49 CEST 2024.