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NotQuiteSane
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PostPosted: Sun Nov 13, 2005 11:35 pm    Post subject: [TIP] Dear cron: quit mailing me! Reply with quote

I use cron to fetch my mail every 15 minutes. of course, being the nice program it is, it emails me to tell me it worked (or didn't work) that's all fine and dandy, but it's pretty self evident that it did or didn't.

I added the following to my .procmailrc file:

Code:
:0: # No mail from cron about fetchmail
* ^Subject:.cron: fetchmail
/dev/null


a quick check of the log shows it worked:

Code:
From nqs@mike.3dogs.homelinux.net  Sun Nov 13 15:15:26 2005
 Subject: cron: fetchmail --all --nokeep --flush
  Folder: /dev/null


there we go. cron can mail the results, and procmail knows where to put it, and I don't have to see them

NQS
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PostPosted: Mon Nov 14, 2005 12:53 am    Post subject: Reply with quote

Thanks for the great tip. Does this apply to those dead.letter files I get after cronning emerge --sync? If so then this will come in handy because those files get quite large after a month of syncing.
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PostPosted: Mon Nov 14, 2005 1:10 am    Post subject: Reply with quote

1U wrote:
Thanks for the great tip. Does this apply to those dead.letter files I get after cronning emerge --sync? If so then this will come in handy because those files get quite large after a month of syncing.


Hmm, I don't think so. I just checked mine, and found at the end a users's password (usually I use password -e so my users can choose their own passwords, but this user is blind, so I manually entered his)!

i've entered
Code:
*/10    *       *       *       *       rm -rf /root/dead.letter


into root's crontab, which will delete the file every 10 minutes. probably need to filter it out, and possibly extend the gap a bit.

NQS
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PostPosted: Mon Nov 14, 2005 1:16 am    Post subject: Reply with quote

That's a quick fix, but it would be nice to figure out how to disable mail from cron, in my case completely. I'll have a look later, perhaps it's not so hard.
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PostPosted: Mon Nov 14, 2005 2:38 am    Post subject: Reply with quote

thanks great tip :D
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PostPosted: Mon Nov 14, 2005 12:46 pm    Post subject: Reply with quote

1U wrote:
That's a quick fix, but it would be nice to figure out how to disable mail from cron, in my case completely. I'll have a look later, perhaps it's not so hard.

That's easy: cron only sends mail, when there is something to send. Make Your lines in crontab to produce no output, and You won't get mail from that job:
Code:
*    3       *       *       *       /sbin/emerge sync > /dev/null 2>&1


- Cocker :wq
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PostPosted: Mon Nov 14, 2005 12:59 pm    Post subject: Reply with quote

1U wrote:
That's a quick fix, but it would be nice to figure out how to disable mail from cron, in my case completely. I'll have a look later, perhaps it's not so hard.


Put
Code:
MAILTO=""
in your crontab

-peter
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PostPosted: Mon Nov 14, 2005 7:53 pm    Post subject: Reply with quote

Cocker68 wrote:
1U wrote:
That's a quick fix, but it would be nice to figure out how to disable mail from cron, in my case completely. I'll have a look later, perhaps it's not so hard.

That's easy: cron only sends mail, when there is something to send. Make Your lines in crontab to produce no output, and You won't get mail from that job:
Code:
*    3       *       *       *       /sbin/emerge sync > /dev/null 2>&1


- Cocker :wq


Or do one of these:

Code:
*    3       *       *       *     /sbin/emerge sync > /dev/null


This way cron will notify you if there was an error, but otherwise keep quiet.
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PostPosted: Mon Nov 14, 2005 7:59 pm    Post subject: Reply with quote

Nifty. :) Thanks.
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PostPosted: Tue Nov 15, 2005 3:11 am    Post subject: Reply with quote

Cocker68 wrote:
This way cron will notify you if there was an error, but otherwise keep quiet.

Thank you everyone for all the tips. However I do not understand how cron will notify me of errors if all of the output is piped to /dev/null? Won't the entire output errors or not simply go there? I would appreciate an explanation.
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PostPosted: Tue Nov 15, 2005 3:32 am    Post subject: Reply with quote

1U wrote:
Cocker68 wrote:
This way cron will notify you if there was an error, but otherwise keep quiet.

Thank you everyone for all the tips. However I do not understand how cron will notify me of errors if all of the output is piped to /dev/null? Won't the entire output errors or not simply go there? I would appreciate an explanation.

If you redirect the output like this:
Code:
*    3       *       *       *     /sbin/emerge sync > /dev/null
Just the output (stdout) gets discarded (note he just used '>'). Errors (stderr) would still be displayed. In the other example above he redirected stdout and stderr both to /dev/null/. See here for a more detailed explanation.

I don't think you want to automatically want to delete dead.letter. AFAIK, dead.letter contains the output that a program (often times this is cron) tried to mail to you but you don't have a mail transfer angent set up so instead it drops everything in dead.letter. This means that it has errors in it that you might care about.
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PostPosted: Tue Nov 15, 2005 3:44 am    Post subject: Reply with quote

Thank you for the explanation allucid. I just have 3 more questions, sorry for taking this offtopic since it's more about bash than his original tip.

1. That link you pointed to didn't explain >>, I know how to use it but I'm curious how it relates to the others if any relation at all.
2. So as long as I do > /dev/null I can expect to see only errors even from commands as simple as rm in my dead.letter?
3. If I do command1 && command2 && command3 > /dev/null will all of those get properly filtered or not?
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PostPosted: Tue Nov 15, 2005 8:52 am    Post subject: Reply with quote

allucid wrote:
I don't think you want to automatically want to delete dead.letter. AFAIK, dead.letter contains the output that a program (often times this is cron) tried to mail to you but you don't have a mail transfer angent set up so instead it drops everything in dead.letter. This means that it has errors in it that you might care about.


I don't belive this is correct, as in mine I found the text to a letter I sent from the command line. IMO, that is not where it belongs.

NQS
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PostPosted: Tue Nov 15, 2005 8:55 am    Post subject: Reply with quote

[quote="1U"]Thank you for the explanation allucid. I just have 3 more questions, sorry for taking this offtopic since it's more about bash than his original tip. -/quote]

Not Allucid, but...

Quote:
1. That link you pointed to didn't explain >>, I know how to use it but I'm curious how it relates to the others if any relation at all.


>> = append
> = overwrite

Quote:
3. If I do command1 && command2 && command3 > /dev/null will all of those get properly filtered or not?


No. be cause what you said to do is "do command 1, then if successfull do Command 2, and if it's sucessfull do comand 3 and send it's results to /dev/null

NQS
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PostPosted: Tue Nov 15, 2005 5:36 pm    Post subject: Reply with quote

NotQuiteSane wrote:
allucid wrote:
I don't think you want to automatically want to delete dead.letter. AFAIK, dead.letter contains the output that a program (often times this is cron) tried to mail to you but you don't have a mail transfer angent set up so instead it drops everything in dead.letter. This means that it has errors in it that you might care about.


I don't belive this is correct, as in mine I found the text to a letter I sent from the command line. IMO, that is not where it belongs.

NQS

You made me more curious so I googled it:
Quote:
If a letter is found to be undeliverable, it is returned to
the sender with diagnostics that indicate the location and
nature of the failure. If mail is interrupted during input,
the message is saved in the file dead.letter to allow edit-
ing and resending. dead.letter is always appended to, thus
preserving any previous contents. The initial attempt to
append to (or create) dead.letter will be in the current
directory. If this fails, dead.letter will be appended to
(or created in) the user's login directory. If the second
attempt also fails, no dead.letter processing will be done.

So I guess this accounts for both your and my case. In my case cron wasn't able to deliver the mail and in your case your user wasn't able to deliver the mail.
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NotQuiteSane
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PostPosted: Fri Nov 18, 2005 3:32 am    Post subject: Reply with quote

allucid wrote:
You made me more curious so I googled it:
Quote:
If a letter is found to be undeliverable, it is returned to
the sender with diagnostics that indicate the location and
nature of the failure. If mail is interrupted during input,
the message is saved in the file dead.letter to allow edit-
ing and resending. dead.letter is always appended to, thus
preserving any previous contents. The initial attempt to
append to (or create) dead.letter will be in the current
directory. If this fails, dead.letter will be appended to
(or created in) the user's login directory. If the second
attempt also fails, no dead.letter processing will be done.

So I guess this accounts for both your and my case. In my case cron wasn't able to deliver the mail and in your case your user wasn't able to deliver the mail.


Again, it doesn't jive. When I sent the letter, I was on the phone with the respondant, and he confirmed getting it almost right away. not more than 2 or 3 minute delay.

most of the time dead.leter doesn't bother me (although i'm curious, need to rtfm, if there is a switch to set the max size). but finding sensitive info in it did. especially since /root is not encrypted

NQS
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PostPosted: Sat Nov 19, 2005 8:53 pm    Post subject: Reply with quote

1U wrote:

3. If I do command1 && command2 && command3 > /dev/null will all of those get properly filtered or not?


No, for that you need to use brackets:
Code:
(command1 && command2 && command3) > /dev/null


**edit

Somehow I didn't realize you were a nazi scumbag. Fuck you idiot! :-)
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