how to set cron job with specific time interval ?

Solution 1:

Cron doesn't understand intervals. You will have to have a separate cron job for each of those.

00 14 * * * ...
50 14 * * * ...
40 15 * * * ...
30 16 * * * ...
20 17 * * * ...
10 18 * * * ...

Solution 2:

Does the specific 50-minute interval matter? Would something like the following work? The first entry in the cron listing below denotes the interval range. So "every 50 minutes". If you need the specific times rather than "once every 50 minutes", then you're better off hardcoding the intervals. Also see: http://www.cyberciti.biz/faq/crontab-every-10-min/

*/50 *    *    *    *       exec /usr/local/bin/script.sh
┬    ┬    ┬    ┬    ┬
│    │    │    │    │
│    │    │    │    │
│    │    │    │    └───── day of week (0 - 7) (Sunday=0 or 7)
│    │    │    └────────── month (1 - 12)
│    │    └─────────────── day of month (1 - 31)
│    └──────────────────── hour (0 - 23)
└───────────────────────── min (0 - 59)