Case statement

Running this script with:

• No option displays the specified message.
• An invalid option displays the specified message.
• A valid option loops through the options to find and display the specified message.
• A colon before the options allows custom messages for missing arguments.
• A colon after an option indicates that an argument is requited.
• Multiple valid options or options and arguments displays the specified messages for each.
• Arguments supplied for options that don’t require them will be ignored.

In this example:

• Custom messages for missing arguments are allowed.
• Options -a and -b and -c and -h are valid.
• All other options are invalid.
• Option -a does not require an argument.
• Option -b requires an argument.
• Option -c requires an argument.
• Option -h does not require an argument.

#!/bin/bash
case "$1" in
	# Valid options:
	-a | -b | -c | -h)
		# Loop through valid options, two of which require arguments:
		while getopts :ab:c:h opt;
			do
				case $opt in
					# Valid option with missing argument:
					:) echo "You must use an argument with the -$OPTARG option.";;
					# Valid option:
					a) echo "You have used the -$opt option.";;
					# Valid option with argument:
					b) echo "You have used the -$opt option with the $OPTARG argument.";;
					# Valid option with argument:
					c) echo "You have used the -$opt option with the $OPTARG argument.";;
					# Valid option:
					h) echo "You have used the -$opt option to display the help text.";;
				esac;
			done;
		;;
	# Missing option:
	"carview.php?tsp=") echo "You have not used an option.";;
	# Invalid option:
	*) echo "You have used the invalid $1 option.";;
esac;

Obligatory Happy Ending

And they all lived happily ever after. The end.