Automating Tasks

Automating tasks saves a system administrator hours of time. It also keeps the load on the computer and network to a minimum by running programs off hours. Some of the things you would want to automate would be backing up file systems, condensing of system logs, restarting the web server, or emptying out /tmp.

The most common UNIX automation is the cron. The /var/spool/cron is a file that is unique for each user. By default you do not have one. To create a cron type crontab -e (the -e is for edit). The format of this file is very specific. The fields in order are:

minute: 0-59
hour: 0-23 (note military time)
day: 1-31
month: 1-12
weekday: 0-6 (0 is Sunday...)

For example, the follow example will print "Hello world!" to the console everyday at 7 am. Note the * matches all values for that field.

0 7 * * * echo "Hello world!" 2>&1 /dev/console
0 8,9,10 * * * echo "Are you still up?" 2 >1& /dev/console

With the use of a comma the above example prints "Are you still up?" at 8, 9, 10 am.
The three flags you can use with crontab:
crontab -e ==> Edit/Create your crontab
crontab -l ==> List the entries in your crontab
crontab -r ==> Delete all entries in your crontab file

Note: Super-User can perform any of these operations on anyone's crontab whereas a user can only use them on his/her own crontab file.

Windows NT does not come with any out of the box software for doing automated tasks, but there are many easy to use programs on the net that can assist you, for example, WINAT that comes with the "Windows NT Resource Kit". Assuming you didn't buy the Resource kit you can use the command line interface and execute an AT command. This command can call batch jobs that run your program and then reschedule your job to run for the next time. This is Windows NT's answer for cron jobs. Here is the syntax:

at [\\computername] time [/every:date[,...] | /next:date[,...] ] command

to remove a scheduled job at #id number /delete

For example, to run a program called "restart" on yellow everyday at 7am on the 13, 14, and 15 of every month type the following.

at \\yellow 7:00 /every:13,14,15 "restart"