bash says '[[:' not found. what does that mean?

Question

While running a bash script, I get this error:

 sh: [[: not found

How can I find what where is the problem?

Answer 1

[[ is a bash command that is not compatible with sh. Run the script with bash instead:

$ bash ./script.sh

Or edit the shebang:

#!/usr/bin/env bash

then:

$ ./script.sh