1FFS(3)                     Linux Programmer's Manual                    FFS(3)
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NAME

6       ffs - find first bit set in a word
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SYNOPSIS

9       #include <strings.h>
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11       int ffs(int i);
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13       #define _GNU_SOURCE
14       #include <string.h>
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16       int ffsl(long int i);
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18       int ffsll(long long int i);
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DESCRIPTION

21       The  ffs()  function  returns the position of the first (least signifi‐
22       cant) bit set in the word i.  The least significant bit is  position  1
23       and  the  most  significant  position  e.g.  32  or 64.   The functions
24       ffsll() and ffsl() do the same but take arguments of possibly different
25       size.
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RETURN VALUE

28       These  functions  return  the position of the first bit set, or 0 if no
29       bits are set in i.
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CONFORMING TO

32       4.3BSD, POSIX.1-2001.
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NOTES

35       BSD systems have a prototype in <string.h>.
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SEE ALSO

38       feature_test_macros(7)
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42GNU                               2003-08-05                            FFS(3)