We can test for the equality or inequality of two strings. For example, one of the ways to test the root user is using the following command:
test $USER = root
We could also write this using the square bracket notation:
[ $USER = root ]
Note that you must put a space between each bracket and the inner testing condition as previously shown.
Equally, we could test for a non-root account with the following two methods:
test ! $USER = root [ ! $USER = root ]
We can also test for the zero values or non-zero values of strings. We saw this in an earlier example in this chapter.
To test if a string has a value, we can use the -n option. We can check to see if the current connection is made through SSH by checking for the existence ...
