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case..esac..in Linux Shell Script

By: Dorris in Linux Tutorials on 2011年01月15日 [フレーム]

The case statement is good alternative to Multilevel if-then-else-fi statement. It enable you to match several values against one variable. Its easier to read and write.

Syntax:

 case $variable-name in
 pattern1) command
 ...
 ..
 command;;
 pattern2) command
 ...
 ..
 command;;
 patternN) command
 ...
 ..
 command;;
 *) command
 ...
 ..
 command;;
 esac

The $variable-name is compared against the patterns until a match is found. The shell then executes all the statements up to the two semicolons that are next to each other. The default is *) and its executed if no match is found. For e.g. write script as follows:

$ cat > car # # if no vehicle name is given # i.e. -z 1ドル is defined and it is NULL # # if no command line arg

if [ -z 1ドル ] 
 then 
  rental="*** Unknown vehicle ***" 
 elif [ -n 1ドル ] 
 then 
 # otherwise make first arg as rental 
  rental=1ドル 
 fi
	case $rental in 
  "car") echo "For $rental Rs.20 per
 k/m";; 
  "van") echo "For $rental Rs.10 per
 k/m";; 
  "jeep") echo "For $rental Rs.5 per
 k/m";; 
  "bicycle") echo "For $rental 20 paisa
 per k/m";; 
  *) echo "Sorry, I can not gat a $rental for
 you";; 
 esac

Save it by pressing CTRL+Dand run it as follows:

$ chmod +x car $ car van $ car car $ car Maruti-800

First script will check, that if 1ドル(first command line argument) is given or not, if NOT given set value of rental variable to "*** Unknown vehicle ***",if command line arg is supplied/given set value of rental variable to given value (command line arg). The $rental is compared against the patterns until a match is found. For first test run its match with van and it will show output "For van Rs.10 per k/m." For second test run it print, "For car Rs.20 per k/m". And for last run, there is no match for Maruti-800, hence default i.e. *) is executed and it prints, "Sorry, I can not gat a Maruti-800 for you". Note that esac is always required to indicate end of case statement.

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