crontab -e
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@yearly		Run once a year at midnight of 1 January			0 0 1 1 *  -
@monthly	Run once a month at midnight of the first day of the month	0 0 1 * *  -
@weekly		Run once a week at midnight on Sunday morning			0 0 * * 0  -
@daily 		Run once a day at midnight					0 0 * * *  -
@hourly		Run once an hour at the beginning of the hour			0 * * * *  -
@reboot		Run at startup	N/A                                                        -
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all 30min =
*/30 * * * * /absolute/path/to/your/parseScript.sh

/etc/init.d/cron start
/etc/init.d/cron restart
/etc/init.d/cron stop