Re-Post: Cron

Note: This is taken from my previous blog - Published on: Jul 11, 2011 @ 10:35

Sounds very computer-ish isn't it? Well, it is… it's actually a scheduling table, something that computer system admins are very familiar with. It's nothing fancy, I could have written this in my wiki, which is what I usually would have done. But, since it's been quite a while since I last write something in this blog, I just feel like putting the info here. I know I'm going to regret this and spend more time transferring this to my wiki later… but I'll do it anyways :-p

A task/job is made of 1 line with 6 items - 5 items/numbers represent time, and the last one is the job/task to be executed. Check it out…

*    *    *    *    *    job/task_to_be_executed
┬    ┬    ┬    ┬    ┬
│    │    │    │    │
│    │    │    │    │
│    │    │    │    └─── weekday (0 - 7) 0/7 => Sunday
│    │    │    └──────── month (1 - 12)
│    │    └───────────── day (1 - 31)
│    └────────────────── hour (0 - 23)
└─────────────────────── minute (0 - 59)

I got the above 'figure' from wikipedia (with minor personal adjustments). To view your current cron jobs, type

crontab -l

So, how do we 'install' a new job? Type

crontab -e

which will open your default terminal editor (e.g. vi) and enter a task in the given format, then save. Voila!

Update20220307 So, after more than 10 years, I finally manged to transfer this to my wiki's mini-blog. Yay! Here are some additional info..

Some examples:

To run binary tool every hour:
```
0 * * * * /path/to/tool <args>...
```

Special cases:

To run binary tool every 5 minutes:
```
*/5 * * * * /path/to/tool <args>...
```
To run binary tool on reboot/startup:
```
@reboot /path/to/tool <args>...
```

computing, linux