a multiple of <tt/res/, then the value is truncated to a multiple of <tt/res/. On
success, zero is returned. On error, -1 is returned and <tt/errno/ is set to an
error code describing the reason for the failure.
a multiple of <tt/res/, then the value is truncated to a multiple of <tt/res/. On
success, zero is returned. On error, -1 is returned and <tt/errno/ is set to an
error code describing the reason for the failure.