What is Cron?
Cron enables users to schedule jobs (commands or shell scripts) to run automatically at a certain time or date. It is commonly used to perform system maintenance or administration, though its general purpose nature means that it can be used for other purposes, such as connecting to the Internet and downloading email.
Cron uses the crontab, a configuration file that specifies shell commands to run periodically on a given schedule.
Crontab has following options:
-l list the crontab
-e edit the crontab
-r remove the crontab
The application “crontab” is used to create and edit cron jobs and the cron daemon checks for cronjobs a the top of every minute.
For example :
crontab -e
It opens the vi editor to enter the cron jobs.
It looks like
# minute (0-59), # | hour (0-23), # | | day of the month (1-31), # | | | month of the year (1-12), # | | | | day of the week (0-6 with 0=Sunday). # | | | | | commands
For Example:
55 10 8 11 * echo “This runs at 10:55 on 8th November”
To list all cron jobs:
crontab -l
To remove a cron job :
crontab -r
For alarm clock, A Command Line Mp3 player can be used here that is mpg321. you may use any mp3 player here but you have to specify what X display to play your player.
For Command Line Mp3 Player,
30 04 * * * mpg321 "/home/sriram/Music/Alarm1.mp3"
For Other Mp3 Player(Audacious):
30 04 * * * env DISPLAY=:0.0 audacious "/home/sriram/Music/Alarm1.mp3"
The asterik can be used (*) to satisfy all variables. I found some good alarm tracks at this site the were perfect for the task
