# [[

> Check file types and compare values.
> Returns 0 if the condition evaluates to true, 1 if it evaluates to false.
> More information: <https://www.gnu.org/software/bash/manual/bash.html#index-_005b_005b>.

- Test if a given variable is equal/not equal to the specified string:

`[[ ${{variable}} {{==|!=}} "{{string}}" ]]`

- Test if a given string conforms the specified glob/regex:

`[[ ${{variable}} {{==|=~}} {{pattern}} ]]`

- Test if a given variable is [eq]ual/[n]ot [e]qual/[g]reater [t]han/[l]ess [t]han/[g]reater than or [e]qual/[l]ess than or [e]qual to the specified number:

`[[ ${{variable}} -{{eq|ne|gt|lt|ge|le}} {{integer}} ]]`

- Test if the specified variable has a [n]on-empty value:

`[[ -n ${{variable}} ]]`

- Test if the specified variable has an empty value:

`[[ -z ${{variable}} ]]`

- Test if the specified [f]ile exists:

`[[ -f {{path/to/file}} ]]`

- Test if the specified [d]irectory exists:

`[[ -d {{path/to/directory}} ]]`

- Test if the specified file or directory [e]xists:

`[[ -e {{path/to/file_or_directory}} ]]`