FFS(3) BSD Library Functions Manual FFS(3)NAME
ffs, ffsl, ffsll, fls, flsl, flsll — find first or last bit set in a bit
Standard C Library (libc, -lc)
ffsll(long long value);
flsll(long long value);
The ffs(), ffsl() and ffsll() functions find the first bit set (beginning
with the least significant bit) in value and return the index of that
The fls(), flsl() and flsll() functions find the last bit set in value
and return the index of that bit.
Bits are numbered starting at 1 (the least significant bit). A return
value of zero from any of these functions means that the argument was
The ffs() function appeared in 4.3BSD. Its prototype existed previously
in <string.h> before it was moved to <strings.h> for IEEE Std 1003.1-2001
The ffsl(), fls() and flsl() functions appeared in FreeBSD 5.3. The
ffsll() and flsll() functions appeared in FreeBSD 7.1.
BSD October 26, 2008 BSD