Bash script countdown timer needs to detect any key to continue

Question

I need to listen for any key press in a countdown timer loop. If any key is pressed then the countdown timer should break out of it\'s loop. This mostly works except for t

Answer 1

The problem is that read would by default consider a newline as a delimiter.

Set the IFS to null to avoid reading upto the delimiter.

Say:

IFS= read -s -N 1 -t 1 key

instead and you'd get the expected behavior upon hitting the Enter key during the read.

Answer 2

I think based on the return code of read, there is a work around for this problem. From the man page of read,

The return code is zero, unless end-of-file is encountered, read times out,
or an invalid file descriptor is supplied as the argument to -u.

The return code for timeout seems to be 142 [verified in Fedora 16]

So, the script can be modified as,

#!/bin/bash
for (( i=30; i>0; i--)); do
    printf "\rStarting script in $i seconds.  Hit any key to continue."
    read -s -n 1 -t 1 key
    if [ $? -eq 0 ]
    then
        break
    fi
done
echo "Resume script"