Does not work to execute command in double brackets in bash

Question

In an attempt to stay consistent i have tried to use double brackets [[ ]] in all my if statements. I did however get into a problem when i was going to check the return value f

Answer 1

The short answer is:

• [ and [[ expect an expression.

• if expects a command.

Saying:

[[ $(command) ]]

would essentially execute:

[[ -n  ]]

which may or may not be what you want. On the other hand, saying:

$command && echo something || echo other

would echo something or other based on the return code of the command (0 and non-zero respectively).