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ucron

Runs commands on a schedule.

Usage

ucron uses a configuration directory to store its state, checked in the following order:

  1. $UCRON_CONFIG environment variable
  2. $XDG_CONFIG_HOME/ucron
  3. $HOME/.config/ucron

The configuration directory must contain a ucrontab file. See below.

Once the ucrontab is set up, simply run ucron to start the daemon.

ucrontab

The ucrontab consists of key-value settings, followed by ---, then a pipe-separated (|) schedule table.

<option>=<value>
---
<interval>|<command>

Options

  • LIFETIME: The maximum lifetime of a ucron process, in seconds.
    • Default: 84600 (1 day)
    • Some systems impose a limit on the maximum lifespan of a process. ucron gets around this by starting another instance of itself after the given time has elapsed.

Schedule

Each schedule entry has an interval in seconds, followed by a command to execute. After ucron is started, the commands will be run periodically at the specified interval.

Example

The following ucrontab would echo 5 every 5 seconds, and 60 every 60 seconds. It would also restart ucron every 20 seconds.

LIFETIME=20
---
5|echo "5"
60|echo "60"

Logs

ucron will log diagnostic messages to $UCRON_CONFIG/ucron.log.

The standard output and error of the running commands is sent to $UCRON_CONFIG/ucron-cmd.log. Each execution is prefixed with a message indicating the start time and command, but since ucron does not wait for the started commands to finish, commands that execute simultaneously may have their output interleaved.

Database

ucron maintains a database of pending commands in $UCRON_CONFIG/ucrondb. Thus, changes to ucrontab won't be reflected immediately. To regenerate the database, send a SIGHUP to the running ucron process.