cronjob is not executing.

I have the following shell script

TIME=$(date +"%H-%M-%d-%m-%y")
tshark -f "udp" -i eth0 -w /root/captures/$PREFIX.cap&
sleep 2m
kill $pid

it runs fine when i execute it from shell.

but when i add it to the cron tab nothing happens.

my crontab entry :
1 */2 * 2 3,4,5 sh /root/

-->tail /var/log/cron
shows that the command has executed .

but nothing happens. i have set executable permission for "all" for and write permission for "all" for /root/captures directory.

Thanks in advance