Bash腳本，比較數字

Question

是否可以將$ip_choice與之前設置的數字進行比較？

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

它的工作就是這樣 - 只有我想知道是否有更優雅的可能性:-)。

Answer 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

Answer 2

您可以使用until ：

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

從help until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