Is double square brackets [[ ]] preferable over single square brackets [ ] in Bash?

Question

A co-worker claimed recently in a code review that the [[ ]] construct is to be preferred over [ ] in constructs like

if [ \"`id -         


        

Answer 1

[[ ]] has more features - I suggest you take a look at the Advanced Bash Scripting Guide for more info, specifically the extended test command section in Chapter 7. Tests.

Incidentally, as the guide notes, [[ ]] was introduced in ksh88 (the 1988 version of the Korn shell).