#!/bin/sh

case $1 in

aa|ab) echo A

;;

b?) echo "B \c"

echo $1;;

c*) echo C;;

*) echo D;;

esac

--------------------------

I ran this program. It just give me the word '' D ''.

This program is to learn how the '' case ' works.

What is '' aa|ab) echo A '' ?


What is ' esac ' stands for?
Could you tell how to run this?
I urge you to tell me the way this progrma works.
-------------------------------------------------------------------------

[nissanka@c83-250-108-234 ~]$ vi temp28
[nissanka@c83-250-108-234 ~]$ chmod 755 temp28
[nissanka@c83-250-108-234 ~]$ ./temp28
D




[nissanka@c83-250-108-234 ~]$ ./temp28 A
D

[nissanka@c83-250-108-234 ~]$ ./temp28 C
D

[nissanka@c83-250-108-234 ~]$ ./temp28 B
D

[nissanka@c83-250-108-234 ~]$ ./temp28 D
D

[nissanka@c83-250-108-234 ~]$ ./temp28 E
D

[nissanka@c83-250-108-234 ~]$ ./temp28 F
D

[nissanka@c83-250-108-234 ~]$ ./temp28 aa
A

[nissanka@c83-250-108-234 ~]$

If $1 (the first commandline parameter sent to the script) is "aa" or "ab", then it will echo "A".
b? checks for a lowercase "b" followed by a single character (b5, for example, would work, but b52 would not).
c* checks for a lowercase "c" followed by anything, or "c" followed by nothing.
* is a catch-all...if none of the previous were found, it uses this option.

You received "D" as the output because you either supplied no parameters, or provided a parameter that was not listed within the case command.
You should see from your tests that the only time you did not get a "D" was when you ran "temp28 aa", which is one of the options listed in the case command.

Thanks mikshaw

Now I understand. I am trying to learn; so your help is badly needed.

By the way, the letters '' fi '' terminates a program.

I guess '' fi '' stands for finish.

Here it is '' esac ''. What is it?

esac is "case" backwards it closes the case statement. just as "fi" is used to close an "if"

fi usually terminates an "if" statement block.
I'd always assumed it was because "fi" = "if" spelt backwards.
There can be multiple fi's in a program, so it does not terminate the program.