Re: interactive vs cron called

Re: interactive vs cron called

[Sweth Chandramouli]

On Thu, Dec 18, 1997 at 03:30:51PM -0500, Jason Zapman II wrote:
> Is there a way to tell if a script is being called by cron or via
> interactive script?  I'm writing something to tell me when disk usage of
> various partitions get's to dangerous levels.  When it's run via cron, I
> want it to mail me the results.  If it's interactive, I want it to print
> the output to the screen.
	why not just have it print output to screen, and in the crontab run the 
command through a pipe to a command-line mailer?
	alternately, write your script to accept a command line option to send 
you mail, and invoke the cron using that option.
	
	-- sweth.

-- 
"Countin' on a remedy I've counted on before
Goin' with a cure that's never failed me
What you call the disease
I call the remedy"  -- The Mighty Mighty Bosstones

Re: interactive vs cron called

[John Riddoch]

> Is there a way to tell if a script is being called by cron or via
> interactive script?  I'm writing something to tell me when disk usage of
> various partitions get's to dangerous levels.  When it's run via cron, I
> want it to mail me the results.  If it's interactive, I want it to print
> the output to the screen.

A rather complex solution, but should work nonetheless.  Find the parent 
process of the script (ie, parent of $$) and then put a name to it.  If the 
parent is /usr/sbin/cron, it's cron invoked, else its interactive.  I'm not 
100% sure if parent process would be the shell (e.g. /usr/local/bin/zsh) but 
you could probably get it's parent process.

How about:

PPID=`ps -Al | nawk -v pid=$$ '{ if ( $4 == pid ) print $5 }'`
PPNAME=`ps -Al | nawk -v ppid=$PPID '{ if ( $4 == ppid ) print $14 }'`

Do a check on PPNAME, et voila!

>From a quick test, if invoked via interactive script, it returns 'zsh' (ie, 
the shell).  If invoked via crontab, it returns 'sh' (since crontab invokes 
everything under /bin/sh).  If you take it a step up, the interactive shell 
will return xxxx (for me it's currently dtterm) and the crontab will return 
cron.  So:

PPID=`ps -Al | nawk -v pid=$$ '{ if ( $4 == pid ) print $5 }'`
PPPID=`ps -Al | nawk -v ppid=$PPID '{ if ( $4 == ppid ) print $5 }'`
PPPNAME=`ps -Al | nawk -v pppid=$PPPID '{ if ( $4 == pppid ) print $14 }'`

and now PPPNAME will be the name of the parent of the parent of the current 
process.

NB: from a quick check on ps -Al, the 11th field doesn't seem to always print; 
I believe off the top of my head there's a way to check the last field which 
would circumvent this.

--
John Riddoch			Programmer/Webmaster
Room C6, School of Computer and Mathematical Science
Robert Gordon University, Aberdeen, AB25 1HG
Telphone: (01224)262721
Email jr@scms.rgu.ac.uk

interactive vs cron called

[Jason Zapman II]

Is there a way to tell if a script is being called by cron or via
interactive script?  I'm writing something to tell me when disk usage of
various partitions get's to dangerous levels.  When it's run via cron, I
want it to mail me the results.  If it's interactive, I want it to print
the output to the screen.

Any ideas?

Thanks;
Jason

-- 
     Jason Price    |     If you want to build a ship, don't drum up people 
      Theta Xi,     |   together to collect wood and don't assign them tasks
   Beta, Alpha 449  | and work, but rather teach them to long for the endless 
 jprice@poboxes.com |    immensity of the sea. -- Antoine de Saint Exupery

Re: interactive vs cron called

[Frank Li]

On 18 Dec 1997, Jason Zapman II wrote:

> Is there a way to tell if a script is being called by cron or via
> interactive script?  I'm writing something to tell me when disk usage of
> various partitions get's to dangerous levels.  When it's run via cron, I
> want it to mail me the results.  If it's interactive, I want it to print
> the output to the screen.
> 
> Any ideas?
> 

actually, just have the program output to the screen since crontab will
automatically E-mail any stdout of the program to you anyway. Try it. 

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Re: interactive vs cron called

[Jason Zapman II]

Jason Zapman II <zapman@cc.gatech.edu> writes:
> When it's run via cron, I want it to mail me the results.

I should have made myself more clear.  I know the output of cron is mailed
to the account for which it is run, but I want it mailed to a DIFFERENT
account.  (script to be run as root, mail going to my more often read
account, as this is something along the lines of a warning bell)

Jason

-- 
     Jason Price    |     If you want to build a ship, don't drum up people 
      Theta Xi,     |   together to collect wood and don't assign them tasks
   Beta, Alpha 449  | and work, but rather teach them to long for the endless 
 jprice@poboxes.com |    immensity of the sea. -- Antoine de Saint Exupery

Re: interactive vs cron called

[Danek Duvall]

Checking the return value of tty -s does the trick for me in a similar
situation (distinguishing between command-line invocation and getting
called as a pipe), as it tells you what's attached to stdin.  I'm pretty
sure that cron runs its jobs with stdin not connected to anything, so that
trick ought to work for you, too.

Perl has a builtin function for this, as the -t flag to the [ function.  It
might be useful to have this functionality in zsh, too, but as it's
obviously possible with a functioning unix setup, it's not necessary.

Danek