shell中的select用法

1. #!/bin/bash
2. echo "Please chose a number, 1: run w, 2: run top, 3: run free, 4: quit"
3. echo
4. select command in w top free quit
5. do
6. case $command in
7. w)
8. w
9. ;;
10. top)
11. top
12. ;;
13. free)
14. free
15. ;;
16. quit)
17. exit
18. ;;
19. *)
20. echo "Please input a number:(1-4)."
21. ;;
22. esac
23. done

执行结果如下：
sh
select.sh
Please chose a number, 1: run w, 2: run top, 3: run free, 4:
quit

1) w
2) top
3) free
4) quit
#? 1
16:03:40 up 32
days,  2:42,  1 user,  load average: 0.01, 0.08, 0.08
USER     TTY      FROM  
           [email protected]   IDLE   JCPU   PCPU WHAT
root     pts/0    61.135.172.68  
 15:33    0.00s  0.02s  0.00s sh select.sh

#? 3
            total  
    used       free     shared    buffers     cached
Mem:       1020328  
  943736      76592          0      86840     263624
-/+ buffers/cache:  
  593272     427056
Swap:      2097144      44196    
2052948
#?

我们发现，select会默认把序号对应的命令列出来，每次输入一个数字，则会执行相应的命令，命令执行完后并不会退出脚本。它还会继续让我们再次输如序号。序号前面的提示符，我们也是可以修改的，利用变量PS3即可，再次修改脚本如下：

1. #!/bin/bash

2. PS3="Please select a number: "
3. echo "Please chose a number, 1: run w, 2: run top, 3: run free, 4: quit"
4. echo
5. select command in w top free quit
6. do
7. case $command in
8. w)
9. w
10. ;;
11. top)
12. top
13. ;;
14. free)
15. free
16. ;;
17. quit)
18. exit
19. ;;
20. *)
21. echo "Please input a number:(1-4)."
22. esac
23. done

如果想要脚本每次输入一个序号后就自动退出，则需要再次更改脚本如下：

1. #!/bin/bash

2. PS3="Please select a number: "
3. echo "Please chose a number, 1: run w, 2: run top, 3: run free, 4: quit"
4. echo
5. select command in w top free quit
6. do
7. case $command in
8. w)
9. w;exit
10. ;;
11. top)
12. top;exit
13. ;;
14. free)
15. free;exit
16. ;;
17. quit)
18. exit
19. ;;
20. *)
21. echo "Please input a number:(1-4).";exit
22. esac
23. done