FFS(3) Library Functions Manual FFS(3)

ffs — find first set bit


#include <strings.h>

int ffs(int i);

The ffs () function shall find the first bit set (beginning with the least significant bit) in i, and return the index of that bit. Bits are numbered starting at one (the least significant bit).

The ffs () function shall return the index of the first bit set. If i is 0, then ffs () shall return 0.

No errors are defined.

None.

None.

None.

None.

The Base Definitions volume of IEEE Std 1003.1-2001 (“POSIX.1”), <strings.h>

First released in Issue 4, Version 2.

Moved from X/OPEN UNIX extension to BASE.

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January 1, 2004 posix.fail