Reading input in bash in an infinite loop and reac

问题:

So I want to wait 1 second for some input (options that i will implement later). Or i want the program to print something(will implement later too). I have run into a problem tho, when trying to read that 1 char for the function, here is my code:

while true
   do read $var -t 1
      case $var in
          ("h")
              help
              ;;
      esac
done

If I try to echo after the case, the program does wait for 1 second, the problem is it doesnt recognise my h input, how would i fix that?

回答1:

I've modified your sample slightly so that it works. There was an error in the read statement. use read varinstead of read $var. This corrected sample will now recognise also the h input.

Related to your question Why it doesn't wait the second (which was btw. hard to determine so i increased the timeout a bit ;-) )? This is because when you enter something, the read timeout is interrupted. It is as the parameter name say's a timeout for the user input. So if the user input's something the timeout is interrupted.

#!/bin/bash

while true 
do
      echo 'wait for input ...'

      read -t 10 var

      echo 'got input ...'

      case $var in
        h)
          echo 'help'
        ;;
      esac
done