changing cron's From: address in emails

[Kevin Kinsey]

Paul Schmehl wrote:
> --On Saturday, October 24, 2009 4:16 AM -0500 Matthew Seaman 
> <m.seaman at infracaninophile.co.uk> wrote:
> 
>> Kelly Martin wrote:
>>>
>>> How can I change the From: address of these emails to "Myserver Cron
>>> Daemon" instead? I know cron runs as the user, so it's not immediately
>>> obvious to me how to change the From: field. Already the subject line
>>> says something like "Cron <root at Myserver> ..." but this doesn't stand
>>> out enough for my tired eyes.
>>
>> Do you control the mail server where you read your e-mail?  Can you use
>> eg. procmail(1) as a delivery agent?  You should be able to match e-mails
>> from Cron and rewrite headers, or deliver cron e-mails into per-machine
>> mailboxes.  Something like this:
>>
>>    :0 h
>>    * From:.*Cron <root@\/[^\.]+
>>      $MATCH
>>
>> The other alternative is to re-write the cron scripts to send e-mail
>> themselves, rather than relying on cron(8) to capture their stdout/stderr
>> and e-mail it for you.  Here's a handy shell programming trick that can
>> make that easier.  Somewhere near the top of the script, you can add
>> something like this:
>>
>>    exec 2>&1 | /usr/sbin/sendmail -oi -t
>>    echo "From: Sender Name <sender at add.ress>
>>    echo "To: <recipient at some.where>
>>    echo "Subject: e-mail from cron job"
>>    echo ""
>>
>> Then everything you print out in the script will be captured as the body
>> of the e-mail and sent to the specified recipient.  You might get some
>> warnings about forgery in the mail headers if the userid the script runs
>> as is not the same as the 'From:' address.
>>
> 
> Why not just echo `hostname` as the first line of every script?  Isn't 
> that what he really wants to know?
> 
> Or echo "This script came from `hostname`"?

Or, on a related note, why have cron(8) do any mailing at all?
Most/all of my management scripts compile a mail message in
/tmp and then send it as the body of a message with mail(1),
so I can have whatever subject header I want, and the envelope
data comes from the user ("usually me at myhost.tld").  Cron sees
nothing because stdout/err is redirected to dev/null.

Kevin Kinsey