Shell basic syntax --- case statement

case statement

• format

case variable in  
value 1) 
    performs an operation 
    ;; 
value 2) 
    perform actions 2 
    ;; 
value 3) 
    perform actions 3 
    ;; 
....
 * ) 
    If the value of a variable value or more is not, this procedure is performed 
    ;; 
Esac

 

• note

• Conventional break is added next to each entry ;;

• Unconditional continues to increase after each one; &

• Conditional continue it every behind the increase ;; &

 

• example

 1 #!/bin/bash
 2 
 3 num=1
 4 case $num in
 5     1 )
 6         echo "1"
 7         ;;
 8     2 )
 9         echo "2"
10         ;;
11     3 )
12         echo "3"
13         ;;
14     * )
15         echo "not 1 2 3"
16         ;;
17 esac 
18 # Output: . 1 
. 19  
20 is ! # / Bin / the bash
 21 is  
22 is NUM = . 1 
23 is  Case $ NUM in 
24      . 1 )
 25          echo  " . 1 " 
26 is          ;; &   # rearwardly matching conditions
 27      2 )
 28          echo  " 2 " 
29          ;;
 30      . 3 )
 31 is          echo  " . 3 " 
32          ;;
 33 is      * )
 34 is          echo  "2. 3. 1 Not " 
35          ;;
 36  Esac 
37 [  # Output:
 38 is      . 1 
39      Not . 1  2  . 3 
40      
41 is # / bin /! the bash
 42 is  
43 is NUM = . 1 
44 is  Case $ NUM in 
45      . 1 )
 46 is          echo  " . 1 " 
47          ; & # unconditionally rearwardly match
 48      2 )
 49          echo  " 2 " 
50          ;;
 51 is      . 3 )
 52 is         echo "3"
53         ;;
54     * )
55         echo "not 1 2 3"
56         ;;
57 esac
58 #输出：1