Test command with the if command

You have seen how to use the test command or the short version [ ]. This test returns zero (true) or non-zero (false).

You will see how to check the returned result using the if command.

Checking strings

You can use the if command with the testcommand 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 are identical" 
else 
echo "Strings are not...