Mastering Linux Shell Scripting - Second Edition

Checking strings

You can use the if command with the test command to check if the string matches a specific criterion:

• if [$string1 = $string2]: This checks if string1 is identical to string2
• if [$string1 != $string2]: This checks if string1 is not identical to string2
• if [$string1 \< $string2]: This checks if string1 is less than string2
• if [$string1 \> $string2]: This checks if string1 is greater than string2

The less than and greater than should be escaped with a backslash as if it shows a warning.

• if [-n $string1]: This checks if string1 is longer than zero
• if [-z $string1]: This checks if string1 has zero length

Let's see some examples to explain how if statements work:

#!/bin/bash if [ "mokhtar" = "Mokhtar" ] then echo "Strings ...