The simpler alternative to cron: Whenjobs

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Article from ADMIN 13/2013

By Oliver Frommel

Cron jobs are essential to managing Linux and Unix systems. However, the syntax is very limited and prone to errors. A modern cron substitute sets out to remove these weaknesses.

One of the many heirlooms from early Unix (since V7 Unix to be exact) is the cron daemon, which still runs regular jobs on today's Linux and BSD systems. Although some alternatives to cron have since been developed, such as fcron [1] and anacron [2], the principle itself has barely changed.

Red Hat programmer Richard W.M. Jones has now broken with tradition and come up with a new cron alternative – a project called Whenjobs. Basically, Whenjobs [3] offers two advantages to cron: simpler syntax for defining jobs and execution times and a system that allows users to define dependencies between jobs.

Prebuilt Whenjobs packages are already available for Fedora 17, but users of other distributions will have to build the tool themselves. To install, you can check Whenjobs out from the Git repository. However, it is easier to download the latest tarfile, because then you don't have to do battle with autoconf and automake.

Because Whenjobs is written in the functional programming language, Ocaml, you will need the matching compiler and a few packages. You can install these with the following command, for example, on Ubuntu 12.10:

sudo apt-get install ocaml ocaml-findlib libcalendar-ocaml libcalendar-ocaml-devcamlp4-extra libocamlnet-ocaml-bin

The ./configure command starts the configuration step, which tells you whether all the necessary packages are installed. During testing, I saw the following error when I ran make: error: Unbound value XDR.safe_add . I resolved this by deleting the generated files lib/whenproto_aux.ml and lib/whenproto_aux.mli. Calling make install installs Whenjobs globally on the system.