With the advent of the GNU Project and Linux, new crons appeared. The most prevalent of these is the Vixie cron, originally coded by Paul Vixie in 1987. Version 3 of Vixie cron was released in late 1993. Version 4.1 was renamed to ISC Cron and was released in January 2004. Version 3, with some minor bugfixes, is used in most distributions of Linux and BSDs.
In 2007, Red Hat forked vixie-cron 4.1 to the cronie project and included anacron 2.3 in 2009.
Other popular implementations include anacron and dcron. However, anacron is not an independent cron program. Another cron job must call it. dcron was made by DragonFly BSD founder Matt Dillon, and its maintainership was taken over by Jim Pryor in 2010.
A webcron solution schedules ring tasks to run on a regular basis wherever cron implementations are not available in a web hosting environment.
On Lubuntu 18.04, I try to figure out what my cron implementation is, like for any other software installed, but fail:
$ cron --version cron: invalid option -- '-' usage: cron $ crontab --version crontab: invalid option -- '-'
I seldom have difficulty in finding out the version of a installed program, and wonder why it is hard for me? How shall I find it out?