04 Dec 2008

Timer In Bash

SYNOPSIS

#function : begin_timer HANDLER_NAME MICROSECONDS CMD_ON_TIMEOUT ARGS...
# @HANDLER_NAME :  handler of timer
# @MICROSECONDS :  micro seconds to wait
# @CMD_ON_TIMEOUT ARGS : command and its arguments to run when timeout
start_timer(){
    [ $# -lt 2 ] && return 1
    HANDLER=$1
    TIMER=$2
    shift 2
    (
        trap exit USR1
        sleep $TIMER
        "$@"
        )&
    eval export $HANDLER=$!
}
export -f start_timer

#function : kill_timer HANDLER_NAME
# @HANDLER_NAME : timer handler to indicate which timer to kill
kill_timer(){
    kill -USR1 ${!1}
}
export -f kill_timer

SAMPLE USAGE

Wait for user input in 5 seconds

#!/bin/sh

trap exit USR1

timeout(){
    echo timeout
    kill -USR1 $1
}

start_timer HANDLER $(( 5 * 1000 * 1000 )) timeout $$
echo -n "READ : "
read F
kill_timer HANDLER
echo "GOT : "$F

Notice

trap TERM HUP QUIT yourself, since if you terminated the process before got any input, timeout event handler will not terminated automatically. You can call kill_timer in you trap handler.