Linux command: Case selection Structure statement

Introduction to the case command:

This command is used for conditional judgment, select structure.

1 . Command format:

Case switch in-----switch variable value

value1)

Statement-----Statement Statement

...

;;

value2)

Statement

...

;;

*)

Statement

....

;;

Esac

2 . Command function:

By selecting the structure, the results of the final output are compared for all possible conditional statements.

3 . Command parameters:

/

4, the command instance:

1, through the keyboard input characters, if the capital letter is a capital letter, lowercase is a lowercase letter.

#!/bin/bash

#

Case $ in

[0-9])

echo "It is digit"

;;

[A-z])

echo "It is lower"

;;

[A-z])

echo "It is Upper"

;;

*)

echo "It is Unknown"

;;

Esac

2, only accept the parameter start, Stop,restart,shutdown.

#!/bin/bash

#

#program

Case $ in

' Start ')

echo "Start server ...";;

' Restart ')

echo "Restart server ...";;

' Stop ')

echo "Stop server ...";;

' Status ')

echo "Running ...";;

*)

echo "' basename $ ' {start|stop|restart|status}";;

Esac

3, write a script, you can accept the option parameters, and then get each option, and the parameters of the options,

And can be based on options and parameters to make a specific operation.

#!/bin/bash

#

Declare-i shownum=0

Declare-i showusers=0

For I in ' seq 1 $# '; Do

If [$#-gt 0]; Then

Case $ in

-H|--HELP)

echo "Usage: ' basename$0 '-h|--help-c|--count-v|--verbose"

Exit 0;;

-v|--verbose)

Let Showusers=1

shift;

-c|--count)

Let Shownum=1

shift;

*)

echo "Usage: ' basename$0 '-h|--help-c|--count-v|--verbose"

Exit 8;;

Esac

Fi

Done

If [$SHOWNUM-eq 1]; Then

echo "Logged users: ' Who |wc-l '."

If [$SHOWUSERS-eq 1]; Then

echo "They is:"

W.H.O.

Fi

Fi

This article is from the "Learn Linux history" blog, please be sure to keep this source http://woyaoxuelinux.blog.51cto.com/5663865/1866118

Linux command: Case selection Structure statement