Bash 脚本，比较数字答案

【问题标题】：Bash script, comparing numbersBash 脚本，比较数字
【发布时间】：2014-04-15 09:22:54
【问题描述】：

是否可以在不设置之前将$ip_choice与数字进行比较？

#!/bin/bash
ip_choice=999
while ! (( $ip_choice <= 233 ))
  do 
    read -p "Enter a valid IP (1-256): " ip_choice
  done

它就是这样工作的——只是我想知道是否有更优雅的可能性:-)。

【问题讨论】：

标签： bash shell ubuntu

【解决方案1】：

#!/bin/bash

while read -r -p "Enter a valid IP (1-256): " ip_choice; do
     (( ip_choice >= 1 && ip_choice <= 256 )) && break
done    
echo "${ip_choice}"

$ ./t.sh
Enter a valid IP (1-256): -1
Enter a valid IP (1-256): 0
Enter a valid IP (1-256): 257
Enter a valid IP (1-256): abc
Enter a valid IP (1-256): 20
20

【讨论】：

【解决方案2】：

你可以使用until:

until ((ip_choice >=1 && ip_choice <= 256)); do
  read -p "Enter a valid IP (1-256): " ip_choice;
done

引用help until:

until: until COMMANDS; do COMMANDS; done

Execute commands as long as a test does not succeed.

Expand and execute COMMANDS as long as the final command in the
`until' COMMANDS has an exit status which is not zero.

Exit Status:
Returns the status of the last command executed.

例如：

$ until ((ip_choice >=1 && ip_choice <= 256)); do
>   read -p "Enter a valid IP (1-256): " ip_choice;
> done
Enter a valid IP (1-256): 0
Enter a valid IP (1-256): 298
Enter a valid IP (1-256): 242

【讨论】：