Bash timer

timeout.sh

#!/bin/bash

convertsecs() {
    ((h=${1}/3600))
    ((m=(${1}%3600)/60))
    ((s=${1}%60))
    printf "%02d:%02d:%02d\n" $h $m $s
}
started=$(date +%s)
current=$started
# timeout: 10 seconds
timeout=$((started+10))
while [ $current -lt $timeout ]; do
    current=$(date +%s)
    diff=$((timeout-current))
    echo "timeout[$(convertsecs $diff)]"
    sleep 1
done

echo "Timeout!"

$ ./timeout.sh 
timeout[00:00:10]
timeout[00:00:09]
timeout[00:00:08]
timeout[00:00:07]
timeout[00:00:06]
timeout[00:00:05]
timeout[00:00:04]
timeout[00:00:03]
timeout[00:00:02]
timeout[00:00:01]
timeout[00:00:00]
Timeout!