Bourne/bash shell scripts: case statement
Contributed by Rex 
Tagged: Bourne shell scripting The case statement is an elegant replacement for if/then/else if/else statements when making numerous comparisons. This recipe describes the case statement syntax for the Bourne shells (sh, ksh, bash, zsh, etc.).
case "$var" in
value1)
commands;
;;
value2)
commands;
;;
*)
commands;
;;
esac
The case statement compares the value of the variable ($var in this case) to one or more values (value1, value2, …). Once a match is found, the associated commands are executed and the case statement is terminated. The optional last comparison *) is a default case and will match anything.
For example, branching on a command line parameter to the script, such as ’start’ or ’stop’ with a runtime control script. The following example uses the first command line parameter ($1):
case "$1" in
'start')
/usr/app/startup-script
;;
'stop')
/usr/app/shutdown-script
;;
'restart')
echo "Usage: $0 [start|stop]"
;;
esac
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Anonymous said on December 31, 2008
case “$1″ in
stdin|
-)
commands
;;
What does stdin|
-) mean here?
Can somebody explain it?
newbie said on April 21, 2009
stdin means “standard input” from the keyboard (file descriptor=0)
stdout means “standard output” to the computer screen (file descriptor=1)
stderr means “standard error”; output for error messages (file descriptor=2)
S.Raghu said on June 13, 2009
How to branch if the value of the variable is ‘*’ ?
For eg parameters passed to a program are 2 numbers and an arithmetical operand.
Patrick said on March 5, 2010
Nice this one was really usefull, but the last one didn’t seem to work for me.
It would whine about a syntax error, so I removes the ! in front and added a *) to catch all the rest, in the case I just did a echo “parameter is valid”
But thanx a lot
Mark said on March 28, 2010
Thanks!
Garry Hurley Jr said on October 11, 2010
Simple. You need to use the escape character on the switch, and you escape it as a parameter. Here is a basic example of that line
#!/bin/bash
case $1 in
%)
echo “%”
;;
*)
echo “*”
;;
*)
echo “none of the above”
;;
esac
Sample output:
snoopy:~>./testBash *
*
My suggestion is to use the ‘x’ for multiplication instead if you don’t want your users to have to escape the ‘*’ every time they use the program.
Sony Sebastian said on January 19, 2011
#!/bin/sh
echo “Enter your choice:”
read username
case “$username” in
’start’)
echo ’starting…………’;;
’stop’)
echo ’stopping………..’;;
‘restart’)
echo ‘restarting………’;;
esac
##################
Output:
./test.sh
Enter your choice:
start
starting…………
Ocho said on January 27, 2012
read input
case “${input}” in
y|Y|yes|YES|Yes)
echo “Do some yes things…”
;;
n|N|no|NO|No)
echo “Do some no things”
;;
*)
echo “${input} is not a valid input. ”
# loop back in via a function or return 1 or quit etc.
;;
esac