linux shell test expression (integer)

	linux shell test expression (integer) -eq is equal to -ne is not equal to -gt is greater than -ge is greater than or equal to -lt is less than -le is less than or equal to < is less than (within double parenthese) (($a < $b)) <= is less than or equal to > is greater than >= is greater than or equal to -z string is null, that is, has zero length -n string is not null