Shell script case in statement

Code

#!/bin/bash
printf "Input integer number: "
read num
case $num in
    1)
        echo "Monday"
        ;;
    2)
        echo "Tuesday"
        ;;
    3)
        echo "Wednesday"
        ;;
    4)
        echo "Thursday"
        ;;
    5)
        echo "Friday"
        ;;
    6)
        echo "Saturday"
        ;;
    7)
        echo "Sunday"
        ;;
    *)
        echo "error"
esac

Output ：

Input integer number:3
Wednesday

grammar

case expression in
    pattern1)
        statement1
        ;;
    pattern2)
        statement2
        ;;
    pattern3)
        statement3
        ;;
    ……
    *)
        statementn
esac

case,in,esac Is the key word ,expression Expression ,pattern Represents a match pattern .

case Will expression The value of is equal to pattern1、pattern2、pattern3 Match one by one ：

• If expression And a pattern （ such as pattern2） The match is successful , Will execute this mode （ such as pattern2） All the following corresponding statements （ This statement can have a , There can be more than one ）, Until I met a double semicolon ;; Just stop ; And then the whole case The statement is executed , The program will jump out of the whole case sentence , perform esac Other subsequent statements .
• If expression No match to any pattern , Then execute *) Subsequent statements （* Represents all other values ）, Until I met a double semicolon ;; perhaps esac It's over .*) It's equivalent to more than one if The last in a branch statement else part .
  there ;; and *) Is equivalent to its Java Medium break and default.

Yes *) Several notes of ：

• Shell case in Statement *) be used for “ Toddy ”, In case expression No match to any pattern ,*) Part can do some “ aftermath ” Work , Or give the user some tips .
• There can be no *) part . If expression No match to any pattern , Then do nothing .

Except for the last branch （ This branch can be a normal branch , It can also be *) Branch ）, Each of the other branches must be preceded by ;; ending ,;; Represents the end of a branch , If you don't write, there will be grammatical errors . The last branch can write ;;, Or not , Because anyway , Execute to esac Will end the whole case in sentence .