Databases Reference
In-Depth Information
Setting Default Editor
The default editor invoked to modify the
cron
table is dependent on the value of your
VISUAL
OS variable. In my
current environment the
VISUAL
variable is set to
vi
:
$ echo $VISUAL
vi
If the
VISUAL
OS variable isn't set, then the value of
EDITOR
is used to define the default editor. Make sure that
either
VISUAL
or
EDITOR
is set to your editor of choice. If neither
VISUAL
nor
EDITOR
is set, your system will default to
the
ed
editor. In this scenario, you'll be presented with the following prompt:
26
<blank prompt>
Press the
Q
key to exit from
ed
. You can have the
VISUAL
or
EDITOR
variable automatically set for you when you
log in to the system. You can also manually set the editor with the
export
command. The following example sets the
default editor to
vi
:
$ export EDITOR=vi
Consider putting the prior line of code in a startup file (such as
.bashrc
) so that your editor is set consistently.
Loading the cron Table from a File
The other way to modify your
cron
table is to load it directly with a file name, using the following syntax:
$ crontab <filename>
Here, the
crontab
utility will load the contents of the specified file into your
cron
table. The recommended steps
to modify your
cron
table with this method are as follows:
Before modifying your
cron
table, first populate a file with the
cron
table's current
contents; for example,
1.
$ crontab -l > mycron.txt
Next, make a copy of the previously created file (
mycron.txt
). This allows you to revert
back to the original file, in the event that you introduce errors and can't readily figure out
what's incorrect. This also provides you with an audit trail of changes to your
cron
table:
2.
$ cp mycron.txt mycron.jul29.txt
Now, edit the
mycron.txt
file with your favorite text editor:
3.
$ vi mycron.txt
For example, to schedule a script named
backup.bsh
to run daily, at 11:05 pm, add the following lines:
#---------------------------------------------------------------------------------
# File backup, dk: 20-jan-14, inserted.
5 23 * * * /home/oracle/bin/backup.bsh
#---------------------------------------------------------------------------------
