BASH: how to pass a default argument if no arguments after the first were passed

Question

I have a bash script with a case statement in it:

case "$1" in 
    bash)
        docker exec -it $(docker-compose ps -q web) /bin/bash
        ;;
    shell)
        docker exec -it $(docker-compose ps -q web) python manage.py shell
        ;;
    test)
        docker exec -it $(docker-compose ps -q web) python manage.py test "${@:2}"
        ;;
esac

On the test command, I want to pass the default argument of apps, but only if the user didn't pass any arguments other than test to the bash script.

So, if the user runs the script like this:

./do test

it should run the command

docker exec -it $(docker-compose ps -q web) python manage.py test apps

However, if they run the script like this:

./do test billing accounts

it should run the command

docker exec -it $(docker-compose ps -q web) python manage.py test billing accounts

How can I test for the existence of arguments after the first argument?

Answer 1

I'd try to use bash variable substitution:

   test)
        shift
        docker exec -it $(docker-compose ps -q web) python manage.py test "${@-apps}"
        ;;

Other way is to check $* instead of $1:

case $* in 
    bash)
         ...
    test)
         docker exec -it $(docker-compose ps -q web) python manage.py test apps
         ;;
    test\ *)
         docker exec -it $(docker-compose ps -q web) python manage.py test "${@:2}"
         ;;

Answer 2

case $1:$# in
(test:1)
    docker $(this is bad) python test apps;;
(test:$#)
    docker $(still bad) python "$@";;
(bash:$#)
    docker ...
esac

Answer 3

something like this would work well

if [ -z "$2" ]
  then
    echo "No argument supplied"
fi

Answer 4

You can just reset your args however you want using set ...

case "$1" in 
    #...
    test)
        [ $# -lt 2 ] && set test apps
        docker exec -it $(docker-compose ps -q web) python manage.py $@
        ;;
esac

Answer 5

If arguments do not have spaces or newlines.
Transform the arguments into an string: "$*", and use that:

f(){ docker exec -it $(docker-compose ps -q web) "$@"; }

case "$*" in
    bash)       f /bin/bash                    ;;
    shell)      f python manage.py shell       ;;
    test)       f python manage.py test apps   ;;
    test\ ?*)   f python manage.py "$@"        ;;
esac

Using a function to manage code (not a variable) and remove repetition.