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crontab -a filename
Install filename as your crontab file. On many systems, this command is executed simply as crontab filename (i.e., without the -a option).
crontab -e
Edit your crontab file, or create one if it doesn't already exist.
crontab -l Display your crontab file.
crontab -r Remove your crontab file.
crontab -v
Display the last time you edited your crontab file. (This option is available on only a few systems.)
crontab -u user
Used in conjunction with other options, this option allows you to modify or view the crontab file of user. When available, only administrators can use this option.
Crontab:
Crontab is the program used to install, deinstall or list the tables used to drive the cron daemon in Vixie Cron. Each user can have their own crontab, and though these are files in /var/spool/cron/crontabs, they are not intended to be edited directly.
Each user has their own crontab, and commands in any given crontab will be executed as the user who owns the crontab. Uucp and News will usually have their own crontabs, eliminating the need for explicitly running su as part of a cron command.
cron is a Linux utility which schedules a command or script on your server to run automatically at a specified time and date. A cron job is the scheduled task itself. Cron jobs can be very useful to automate repetitive tasks.
For example, you can set a cron job to delete temporary files every week to conserve your disk space. Some programs, such as Drupal, may even require you to set up a cron job to perform certain functions.
Scripts executed as a cron job are typically used to modify files or databases. However, they can perform other tasks that do not modify data on the server, like sending out email notifications.
Advantages of a cron job:
• You more easily have control over when it runs. You control the minute, hour, day, etc, that it will execute
• It's easier to write the code and to manage its operation. It eliminates the looping and timing logic in the task, and you run crontab to change the timing or shut it off.
• It's not occupying memory in your system when it's not running.
• If it fails and exits for some reason, it will start up again when the proper time comes.
The crontab is a list of commands that you want to run on a regular schedule
corn tab is used to schedules a command or script on your server to run automatically at a specific time and date
Cron tab is used to automate cron programs as per our requirement
Cron is a daemon that can be used to schedule the execution of recurring jobs according to a combination of the time, day of the month, month, day of the week, and week.
Cron Tab is programme which we can use to run scheduled tasks automatically on hourly, daily, monthly, yearly basis. Just put one entry in the cron tab file and we are free to forget it.
We use crontab for automation of the work specifying commands/scripts to run automatically on specific time.
Crontab is a scheduler, which can be used to automate tasks at scheduled time.
one can create a cron tab job in linux/unix to run a specific script with certain interval. The script can be run at specific hour of day as well.
To schedule the run of script.
