Updated: 2021/Apr/14


FFS(3)                     Library Functions Manual                     FFS(3)

NAME
     ffs - find first bit set in a bit string

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <strings.h>

     int
     ffs(int value);

DESCRIPTION
     The ffs() function finds the first bit set in value and returns the index
     of that bit.  Bits are numbered starting from 1, starting at the right-
     most bit.  A return value of 0 means that the argument was zero.

SEE ALSO
     bitstring(3), ffs32(3), popcount(3)

STANDARDS
     The ffs() function conforms to IEEE Std 1003.1-2001 ("POSIX.1").

HISTORY
     The ffs() function appeared in 4.3BSD.  The prototype for it existed
     previously in the <string.h> header before it was moved to <strings.h>
     for POSIX compliance.

NetBSD 9.99                     April 28, 2010                     NetBSD 9.99