if

Performs conditional processing in shell scripts.

See also: `test`, `[`.

• Execute the specified commands if the condition command's exit status is zero:

if {condition_command}; then {echo "Condition is true"}; fi

• Execute the specified commands if the condition command's exit status is not zero:

if ! {condition_command}; then {echo "Condition is true"}; fi

• Execute the first specified commands if the condition command's exit status is zero otherwise execute the second specified commands:

if {condition_command}; then {echo "Condition is true"}; else {echo "Condition is false"}; fi

• Check whether a [f]ile exists:

if [[ -f {path/to/file} ]]; then {echo "Condition is true"}; fi

• Check whether a [d]irectory exists:

if [[ -d {path/to/directory} ]]; then {echo "Condition is true"}; fi

• Check whether a file or directory [e]xists:

if [[ -e {path/to/file_or_directory} ]]; then {echo "Condition is true"}; fi

• Check whether a variable is defined:

if [[ -n "${variable}" ]]; then {echo "Condition is true"}; fi

• List all possible conditions (`test` is an alias to `[`; both are commonly used with `if`):

man [

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