FFS(3) Library Functions Manual FFS(3)
ffs -- find first bit set in a bit string
Standard C Library (libc, -lc)
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.
bitstring(3), ffs32(3), popcount(3)
The ffs() function conforms to IEEE Std 1003.1-2001 (``POSIX.1'').
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 6.1.5 April 28, 2010 NetBSD 6.1.5