Example of using the while loop in Shell

1. #! /Bin/sh
2. # Filename: 2.sh
3. B = 9
4. E = 15
5. Tmpb = $ B
6. While [$ tmpb-Le $ E]
7. Do
8. Echo $ tmpb
9. # Tmpb = 'expr $ tmpb + 1' // OK
10. Tmpb = $ (expr $ tmpb + 1)
11. Done

After the script is executed, the output result is:

9
10
11
12
13
14
15

 

Note: The functions of row 9th are the same as those of row 10th.

 

 

The following example uses a loop. You must enter a number to exit.

1. #! /Bin/sh
2. # Filename: B
4. While:
5. Do
6. Echo-n "input a number :"
7. Read Val
8. Expr $ Val + 1>/dev/null 2>
9. Res = $?
10. If ["$ Val" = ""] | ["$ res "! = "0"]; then
11. Echo "what you input is not a number! "
12. Else
13. Echo "what you input is: $ Val"
14. Break;
15. Fi
16. Done