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Manual Reference Pages  - FFS (3)

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ffs - find first bit set in a word

CONTENTS

Synopsis
Description
Notes

#include <strings.h> 



int ffs(int i); 



#define _GNU_SOURCE 




#include <string.h> 



int ffsl(long int i); 



int ffsll(long long int i); 

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 e.g. 32 or 64. The functions ffsll() and ffsl() do the same but take arguments of possibly different size.

These functions return the position of the first bit set, or 0 if no bits are set.

BSD 4.3, POSIX 1003.1-2001.

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

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