Learning Linux Shell Scripting - Second Edition

Using the test command

Let's look at the following example to check the content or value of expressions:

    $ test $name=Ganesh
    $ echo $?
    0 if success and 1 if failure.

In the preceding example, we want to check whether the content of the variable name is the same as Ganesh and ?. To check this, we have used the test command. The test command will store the result of the comparison in the ? variable.

We can use the following syntax for the preceding test command. In this case, we used [ ] instead of the test command. We've enclosed the expression to be evaluated in square brackets:

    $ [[ $name = Ganesh ]]      # Brackets replace the test command
    $ echo $?
    0

During the evaluation of expressions by test, we can even use wildcard expressions:

    $ [[ ...