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Scheduling cronjobs

Cron is the name of a unix program that enables users to schedule commands or scripts to run automatically at a specified time/date.

To schedule a script to run you add an entry to your crontab file. Each entry in cron is a line made up of six fields, each separated by a space. Althought there is often a system crontab file located in '/etc/crontab' you will probably edit your own user crontab file. Rather than viewing and editing the file directly, use the crontab utility. You can list the contents using the command 'crontab -l'. Assuming you can use vi you can also edit the contents of the file using 'crontab -e'. If you don't want to use vi you can always change your default editor to something you are familiar with. See Changing your default editor.

The nightly cmiss build jobs are scheduled using cron. To change when they are run you will need to edit the appropriate entry in the crontab file. If you need to do this it may be helpful to review the crontab syntax. See for a brief review. For a comprehensive introduction see

For convenience here are the six fields from wikipedia:

# Use the hash sign to prefix a comment
# +---------------- minute (0 - 59)
# |  +------------- hour (0 - 23)
# |  |  +---------- day of month (1 - 31)
# |  |  |  +------- month (1 - 12)
# |  |  |  |  +---- day of week (0 - 7) (Sunday=0 or 7)
# |  |  |  |  |
# *  *  *  *  *  command to be executed

The contents of the crontab file for esu8 is as follows:

# Compilation and testing.
0 1  * * * /hpc/cmiss/cmiss_utils/cronjobs/

# Collect and summarize testing results.
50 6 * * * ssh bioeng22 exec /hpc/cmiss/cmiss_utils/cronjobs/

This runs the script at 1:00am every day and the script at 6:50am every day.

If you need to disable the scripts from running over the weekend (eg because of server maintenance) you could edit the crontab file so the scripts are run every week day only:

# Compilation and testing.
0 1  * * 1-5 /hpc/cmiss/cmiss_utils/cronjobs/

# Collect and summarize testing results.
50 6 * * 1-5 ssh bioeng22 exec /hpc/cmiss/cmiss_utils/cronjobs/