osf1 man page for ffs

ffs(9r) 																   ffs(9r)

NAME
       ffs - General: Finds the first set bit in a mask

SYNOPSIS
       int ffs(
	       long mask );

ARGUMENTS
       Specifies a bit mask with 0 (zero) or more bits set.

DESCRIPTION
       The  ffs  routine returns the bit position of the first bit you set in the mask argument.  The scan proceeds from the least significant bit
       to the most significant bit of the mask.

NOTES
       The ffs routine duplicates the behavior of the ffs instruction on the DIGITAL VAX series or computers.  It is not present in  architectures
       that implement its function in hardware or through compiler inline substitution.

       The  ffs  routine is useful for translating bits in a bit mask into bit positions. For example, the signal handling code uses it to analyze
       the signal mask.

RETURN VALUES
       Upon successful completion, ffs returns the bit position of the first bit set in the mask. If no bits were set in the mask, ffs returns the
       value 0 (zero).

																	   ffs(9r)