if

Performs conditional processing in shell scripts. See also: test, [. More information: https://www.gnu.org/software/bash/manual/bash.html#Conditional-Constructs.

• 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 test