ffs(9r)ffs(9r)NAMEffs - 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 sub‐
stitution.
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)