CIS241

System-Level Programming and Utilities

bash Conditionals

Erik Fredericks, frederer@gvsu.edu
Fall 2025

Based on material provided by Erin Carrier, Austin Ferguson, and Katherine Bowers

if

General form:

if CONDITION
then
  # do the things
fi

or:

if CONDITION; then
  # do the things
fi

CONDITION?

Think of your if tests - those are conditionals

if [ $1 -lt 10 ]; then
  # do things here
fi

What does this do?

MORE

A reference: https://ryanstutorials.net/bash-scripting-tutorial/bash-if-statements.php

Conditions

• Can also run man test

Alternative - arithmetic expression!

if (( $1 < 10 )); then
  # do things
fi

And then, the else

if CONDITION; then
  # do thing 1
elif CONDITION2; then
  # do thing 2
else
  # do thing 3
fi

Boolean operators

if [ $1 -lt 10 ] && [ $1 -gt 0 ]; then
  # do stuff
fi
	
if [ -z $2 ] || [ $2 = “start” ]; then
  # do stuff
fi

And finally, the case

test1="HELLO"

case $test1 in
HELLO | HI)
  echo "case successful: $test1" ;;
ANOTHER)
  echo "a different case" ;;
"AND ANOTHER")
  echo "different yet again";;
*)
  echo "default case" ;;
esac

https://linuxize.com/post/bash-case-statement/