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 withif
):man [
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