FFS(9) Basic C Library Functions FFS(9)
NAME ffs - find first set bit in word
SYNOPSIS int ffs(int x);
ARGUMENTS x the word to search
DESCRIPTION This is defined the same way as the libc and compiler builtin ffs routines, therefore differs in spirit from the other bitops.
ffs(value) returns 0 if value is 0 or the position of the first set bit if value is nonzero. The first (least significant) bit is at position 1.
COPYRIGHT Kernel Hackers Manual 2.6. September 2014 FFS(9)