What is Cron Job?
The word Cron actually originated from the word chronograph, which means a time piece. A Cron is actually a job scheduler which is used to schedule time-based jobs. It is also called a Cron Daemon. We can say that it is an automatic program which makes our work easier. It is mostly used in the UNIX and LINUX computer operating systems. It helps the users to schedule jobs so that the jobs can be run automatically at a preset point of time. It keeps on repeating itself; it does not need manual instructions again and again. Actually, it automates our system. It can be used for various purposes which includes connecting to the Internet.
The Cron is actually a program which helps users to execute commands automatically at a preset point of time. A Cron table is built into the UNIX and Linux operating systems, which contain a list of Cron functions.
History:
1. The first version of the Cron was written by Brian Kernighan. It was written for the Version7 Unix. It was a system service which was later called Daemons. In the 1970’s, an experiment was carried out to increase the Cron’s service but it was found that it was making the system slow.
2. The Cron’s next version was designed to increase its capabilities. It was actually designed for all the users of the UNIX system. It now provides multi-user capabilities.
3. Then the modern versions of the Cron came into the market. It was basically designed for the Linux operating system. The most important version was the Vixie Cron, which was originally designed by Paul Vixie in 1987. The third version of the Vixie Cron (Version 3) was released in 1993. The name of the Version 4.1 was changed to ISC Cron and it was released in January 2004.
4. The Anacron and the Fcron were also the important Crons of that time. The Anacron had one disadvantage that it depended on the other Crons to work.
Advantages
1. It reduces human efforts.
2. It is easy to understand.
