Case Statement

case Statement
The case statement provides a way to avoid using if..then..else statements.  It allows users to enter a text string, then evaluate that string and provide the option that the string indicates.  The case statement is matched against a number of values until a match is found.    When a match is found, the commands are executed until the double semicolons “;;” are reached.  Then those commands after the “esac” are executed.  If there is no match it executes the commands after the  “*)” until the double semicolons.  The “*)” acts the same way as the “else” in a if ...then clause.

Lesson 13 |   Lesson 14

case $VARIABLE in
match_1)
commands_to_execute
;;
match_2)
commands_to_execute
;;
match_3)
commands_to_execute
;;
*)  Optional Information
commands_to_execute_for_no_match
;;
esac


term_color.sh
This simple script can be run in a tty to that you can change the color to be more easily read.  Note that the tty uses 8
colors so you will not get the most beautiful output.  The 8 clors are; black, white, red, blue,green, yellow, magenta, and cyan.


#!/bin/bash

echo -n "Choose Background Color for Terminal(b-black,g-grey,y-yellow): "
read color
case "$color" in
b)
setterm -background black -foreground white -store
;;
g)
setterm -background white -foreground black -store
;;
y)
setterm -background yellow -foreground red -store
;;
*)
echo "I do not understand"
;;
esac

These lines provide text to help the user make a choice on color.  When the user enters the choice it is read into the variable color.

echo -n "Choose Background Color for Terminal(b-black,g-grey,y-yellow): "
read color

The case command is differentiated by the letter that was entered to create the variable "color" and followed by a ")" to indicate that is the option.  Note the case variable captures the user choice for background and then executes a command that not only sets the background but also sets the forground color as well.  The "-store" makes it a change until it is returned to the normal setting by "b" choice for a black background.  Each option executes the command that follows until it reaches the ";;" or esac.


case "$color" in
b)
setterm -background black -foreground white -store
;;
g)
setterm -background white -foreground black -store
;;
y)
setterm -background yellow -foreground red -store
;;

This takes all entries that do not fit the three specified and indicates to the user they have made an error.

*)
echo "I do not understand"