all of the above is one command so you can check the outcome which should be the output of the dc command...
~$ usage=$(gconftool -g /cellui/settings/datacounter/general/gprs_home_notification_period_UI) ; tx=$(gconftool -g /cellui/settings/datacounter/transfer/gprs_home_tx_bytes) ; rx=$(gconfto ol -g /cellui/settings/datacounter/transfer/gprs_home_rx_bytes) ; total=$(($tx+$rx)) ; `dc $total $usage / p` dc: Could not open file 242418745 dc: Could not open file 1000000000 dc: Will not attempt to process directory / dc: Could not open file p ~ $