Conditional Expressions

Syntax

• [[ -OP $filename ]]
• [[ $file1 -OP $file2 ]]
• [[ -z $string ]]
• [[ -n $string ]]
• [[ “string1” = =“string2” ]]
• [[ “$string1” == $pattern ]]

Remarks

The [[ … ]] syntax surrounds bash built-in conditional expressions. Note that spaces are required on either side of the brackets.

Conditional expressions can use unary and binary operators to test properties of strings, integers and files. They can also use the logical operators &&, || and \!.