Cron is a job scheduler that allows users to run commands periodically.

Cron is a daemon that runs periodic scheduled jobs.

Use the crontab command to edit the table of scheduled jobs.

Use to schedule a job for one execution only at a specific date.

Common pitfalls

If a command works when you type it in a terminal but not from a crontab, here are some common reasons:

  • Cron provides a limited environment, e.g., a minimal $PATH.
  • Cron uses /bin/sh, which may not be the shell you normally use.
  • Cron treats the % character specially (it is turned into a newline in the command).

Further reading

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