How to detect Enter key or no input in Bash?-CodePudding

I want to write a script to run a program after X seconds, it can be stopped if user press Enter

But it cannot detect whether user pressed Enter key or no input

#!/bin/bash
seconds=$((5))
holder='000'
while [ $seconds -gt 0 ]; do
    if [[ $holder = "" ]]; then 
        echo "Stop"
        exit
    else
        echo "Start in $seconds seconds, Press Enter to stop"
    fi
    IFS= read -r -t 1 -n 1 -s holder && var="$holder"
    : $((seconds--))
done
echo Start

CodePudding user response：

If timeout happens, read fails (i.e. returns a non-zero return code). So it is as simple as this:

if read -t 1
then
  echo Enter pressed
else
  echo Timeout happened
fi

So in your case, something like this, maybe?

seconds=5
while [[ "$seconds" -gt 0 ]]; do
    echo "Start in $seconds seconds, Press Enter to stop"
    if read -t 1 -s
    then
        echo Stop
        exit
    else
        ((seconds--))
    fi
done
echo Start