Shell Programming and Scripting

declare -i DEFINT=1
declare -i DEFDELAY=1
declare -i timeout=DEFTOUT
declare -i interval=DEFINT
declare -i delay=DEFDELAY

if (($# == 0 || interval <= 0)); then
    printUsage
    exit 1
fi

(
    ((t = timeout))

    while ((t > 0)); do
        sleep $interval
        kill -0 $$ || exit 0
        ((t -= interval))
    done

    kill -s SIGTERM $$ && kill -0 $$ || exit 0
    sleep $delay
    kill -s SIGKILL $$
) 2> /dev/null &

DEFINT=1
DEFDELAY=1
timeout=${DEFTOUT}
interval=${DEFINT}
delay=${DEFDELAY}

if [ $# -eq 0 ] || [ ${interval} -le 0] ; then
    echo "ERROR: WRONG USAGE!"
    exit 1
fi

t=${timeout}

    while (($t > 0)); do
        sleep $interval
        kill -0 $$ || exit 0
        (($t -= $interval))
    done

    kill -s SIGTERM $$ && kill -0 $$ || exit 0
    sleep $delay
    kill -s SIGKILL $$

DEFINT=1
DEFDELAY=1
timeout=DEFTOUT
interval=DEFINT
delay=DEFDELAY

if [ $# -eq 0  ] || [ $interval -le 0 ]; then
    printUsage
    exit 1
fi

{
    t=$timeout

    while [ $t -gt 0 ]; do
        sleep $interval
        kill -0 $$ || exit 0
        t=$((t - interval))
    done

    kill -s SIGTERM $$ && kill -0 $$ || exit 0
    sleep $delay
    kill -s SIGKILL $$
} 2> /dev/null &

let DEFINT=1
let DEFDELAY=1
let timeout=${DEFTOUT}
let interval=${DEFINT}
let delay=${DEFDELAY}

if [ $# -eq 0 ] || [ ${interval} -le 0]

if [  \ ( $# -eq 0 \) -o \(${interval} -le 0 \) ]
then
...

#!/bin/sh
DEFINT=1
DEFDELAY=1
timeout=DEFTOUT
interval=DEFINT
delay=DEFDELAY

if [ $# -eq 0 -o $interval -le 0 ]; then
    printUsage
    exit 1
fi

(
    t=timeout

    while [ $t -gt 0 ]; do
        sleep $interval
        kill -0 $$ || exit 0
        t=`expr $t - $interval`
    done

    kill -s SIGTERM $$ && kill -0 $$ || exit 0
    sleep $delay
    kill -s SIGKILL $$
) 2> /dev/null &