UNIX for Dummies Questions & Answers

Hi All,

Ref: "build crontab from a text file" in same forum. (I am not allowed to post URL's in the first post)

We are reorganizing our UNIX Crontab file by first making changes in a word pad text file. The intent is to then copy it back to Crontab. Will this work? Copy and Paste does not seem to work.

From the crontab man page -

Code:

Code:

 
crontab [file] Create or replace your crontab file by copying the specified file, or standard input if file is omitted or - is specified as file , into the crontab directory, /var/spool/cron/crontabs. The name of your crontab file in the crontab directory is the same as your effective user name.

So, something like this:


Code:

Code:

cat mynotepadfile | crontab -mynotepadfile

will have to have ALL of the entries needed from the old crontab, because this wipes all of the lines in the existing crontab file.
-----------------------------

My script does many actions as root. A part of this script is to add a new crontab entry for a normal user.

I used this method and now need to transfer "mynotepadfile" to crontab of "myuser". But the method "crontab [file]" only works for the user invoking it. So this will edit root's crontab, but not someone else's. At the same time, the whole script cannot be executed as non-root.

How would the syntax "cat mynotepadfile | crontab -" change?

Thank you.

It'd be better just to edit it on the UNIX system with crontab -e -- typing text into a black window really isn't that different than typing text into a white one.

If you insist on a solution that edits in windows, you don't need to redirect the file into crontab when you give it a file name:

Code:

crontab filename

Be very very sure that you're not giving cron a file filled with garbage carriage returns after you've edited it on windows! Windows text files are not the same as UNIX ones, Windows uses \r\n in the CPM/DOS tradition.

Hi Corona688,

Thank you for your reply.

But I did a mistake by referring another thread, as I created an impression that I am working in Windows. There is no Windows system in the picture. I would like to clarify the situation. The system runs on AIX. I referred to the thread because I got this when I searched a solution for this issue.

My requirement is to run a script as root, which adds a job to a normal user's cron file.
But the constraints are:
1)Other portions of the script needs root privileges. So normal user cannot execute it.
2)It is not possible to manually edit cronfile, because this and other steps should be part of a big script that would be executed on a number of systems.
3)Root cannot give the command

Code:

cat /tmp/tmp_cronfile | crontab -

(where /tmp/tmp_cronfile contains the text to add the job to the normal user's cron file)
because this command ends up in changing root's cron file and not the normal user's cron file.

The command

Code:

crontab filename

will also not help for the same reason.

My question is how to modify the above command in such a way that it modifies a normal user's cron file, even while running as root.
Is it something to do with the -l or -u flags of the crontab command?

Thanks again.

Yes, -u tells it the user.

You can't just add text to a crontab with - because that will replace the entire cron table.

All these questions and more can be more rapidly answered by reading man crontab.

Hi Corona688,

I asked for help as I didnt get a clue on the syntax if the user is other than invoking user.

Thanks.

-u user

Yes I understand it is -u for another user . But my question was about using this syntax in this particular case, i.e within a script?.

Anyway, thanks for your help Corona688 .