[[

Check file types and compare values. Returns a status of 0 if the condition evaluates to true, 1 if it evaluates to false. More information: https://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}} ]]