Shell Programming Case Statements

Bash Script Programming:

Case statement:

Multi-Branch If statement:

if CONDITION1; Then

Branch 1

Elif CONDITION2; Then

Branch 2

...

else CONDITION; Then

Branch N

Fi

Example 1: Display a menu to the user;

CPU) Display CPU information

MEM) Display Memory information

Disk) Display disks information

Quit) quit

Requirements: (1) Prompt the user to give their own choice;

(2) The correct choice will give the corresponding information; otherwise, prompt to re-select the correct option;

#!/bin/bash

#

Cat << EOF

CPU) Display CPU information

MEM) Display Memory infomation

Disk) Display disks information

Quit) quit

===============================

Eof

Read-p "Enter your option:" option

While ["$option"! = "CPU"-a "$option"! = "Mem"-a "$option"! = "Disk"-a "$option"! = "Quit"]; Do

echo "CPU, mem, disk, quit"

Read-p "Enter your option again:" option

Done

If ["$option" = = "CPU"]; Then

Lscpu

elif ["$option" = = "mem"]; Then

Free-m

elif ["$option" = = "Disk"]; Then

Fdisk-l/dev/[hs]d[a-z]

Else

echo "Quit"

Exit 0

Fi

Syntax format for Case statements:

Case $VARAIBLE in

PAT1)

Branch 1

;;

PAT2)

Branch 2

;;

...

*)

Branch N

;;

Esac

Case supports GLOB-style wildcard characters:

*: Any character of any length;

?: any single character;

[]: Any single character in the range;

A|b:a or B;

Example: Write a service framework script;

$lockfile, Value/var/lock/subsys/script_name

(1) This script can accept start, stop, restart, status of one of the four parameters;

(2) If the parameter is not four, then the use of help after the exit;

(3) Start, create Lockfile, and show start, stop, delete lockfile, and display stop, restart, delete this file before you create this file, and then display the restart complete; status, if Lockfile exists, The running is displayed, otherwise, it is displayed as stopped.

#!/bin/bash

#

# Chkconfig:-50 50

# description:test Service Script

#

prog=$ (basename)

lockfile=/var/lock/subsys/$prog

Case $ in

Start

If [-f $lockfile]; Then

echo "$prog is running yet."

Else

Touch $lockfile

[$?-eq 0] && echo "Start $prog finshed."

Fi

;;

Stop

If [-f $lockfile]; Then

Rm-f $lockfile

[$?-eq 0] && echo "Stop $prog finished."

Else

echo "$prog is not running."

Fi

;;

Restart

If [-f $lockfile]; Then

Rm-f $lockfile

Touch $lockfile

echo "Restart $prog finished."

Else

Touch-f $lockfile

echo "Start $prog finished."

Fi

;;

Status

If [-f $lockfile]; Then

echo "$prog is running"

Else

echo "$prog is stopped."

Fi

;;

*)

echo "Usage: $prog {start|stop|restart|status}"

Exit 1

Esac

Shell Programming Case Statements