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Quick links About
crontab
Syntax
Examples
Related commands
Linux / Unix main page
About crontab
List of files that you want to
run on a regular schedule.
Syntax
crontab [-e] [-l] [-r]
[filename]
| -e |
edit a copy of the current user's crontab file, or creates an empty file to edit if crontab does not exist. When editing is complete, the file is installed as the user's crontab file. If a user- name is given, the specified user's crontab file
is edited, rather than the current user's crontab file; this may only be done by a super-user. The
environment variable EDITOR determines which editor is invoked with the -e option. The default editor is
ed. Note that all crontab jobs should be submitted using crontab ; you should not add jobs by just editing the crontab file because cron will not be aware of changes made this way. |
| -l |
list the crontab file for the invoking user. Only a super-user can specify a username following the -r or -l options to remove or list the crontab
file of the specified user. |
| -r |
remove a user's crontab from the crontab |
| filename |
The filename that contains the commands to run. |
Lines that can be in the crontab file.
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).
Examples
crontab
-e = edits the crontab file to be used.
0 12 14 2 * mailx john%Happy Birthday!%Time for lunch.
Below is a table that represents what each of the
above fields are for.
| min |
hour |
dayofmonth |
monthofyear |
dayofweek |
command |
| 0 |
12 |
14 |
2 |
* |
mailx john%Happy Birthday!%Time for lunch. |
| Options |
Explanation |
| * |
Is treated as a wild
card. Meaning any possible value.
|
| */5 |
Is treated as ever 5 minutes,
hours, days, or months. Replacing the 5 with another
numerical value will change this option. |
| 2,4,6 |
Treated as an OR, so if
placed in the hours, this could mean at 2, 4, or 6
o-clock. |
| 9-17 |
Treats for any value between
9 and 17. So if placed in day of month this would be days 9
through 17. Or if put in hours it would be between 9 and 5. |
If you wish to create a task to be performed once
later during the day you may wish to consider using the at
command.
Related commands
at |
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| Resolved |
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