Spring Into Linux®

Testing Conditions

The shell provides a test command for testing conditions. The test commands test expressions to see whether the expression is true, as follows:

test $age -eq 21
[ $age -eq 21 ]

The two statements are equivalent. This chapter uses the second format. A space is required before and after each square bracket. The test returns true if $age equals 21.

Table 19-1 lists the options you can use to test values.

Table 19-1. Options for Use When Testing Expressions

Option	Tests for	Example
=	equal text strings	[ $name = "John" ]
!=	non equal text strings	[ $name1 != $name2 ]
-eq	equal integers	[ $age -eq $adult ]
-gt	integer1 is greater than integer2	[ $age -gt 20 ]
-ge	integer1 is greater than or equal to integer2	[ $age -ge 21 ]
-lt	integer1 is less than ...