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808 posts

Ultimate Geek
+1 received by user: 78


Topic # 107003 4-Aug-2012 17:05 Send private message

I'm running a headless ArchLinux server, access via SSH (putty on Windows).
I've got a small script that runs every minute, through crontab.  I know this works because I have it flashing an LED (through a simple C program).  I also want to display some text on a console when a user is logged in which is what I need some help with please.

The C program has a printf statement within it that succesfully outputs to the console when I run it manually, but when executed via the crontab scheduled script nothing shows up.

Similarly, including an echo command in the script shows nothing on a console that I have SSH'd into.

Is there anyway that I can tell the script to output everything to a specific user's console, or anywhere at all really where I can see it if I log in via SSH?





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mjb

922 posts

Ultimate Geek
+1 received by user: 21

Trusted

  Reply # 667563 4-Aug-2012 18:34 Send private message

stdout for a cronjob is usually captured and emailed to the user account that owns the cronjob. If you have your mail system configured correctly, then you'll find the messages in the mailbox of your user account probably.

Anyway, to answer your question, try piping the output from your program to `wall`. something like so:

0 * * * * * /path/to/your/program | wall

wall stands for "write all", which will send a message to all logged in users. Check the manpage for more info.





contentsofsignaturemaysettleduringshipping



808 posts

Ultimate Geek
+1 received by user: 78


  Reply # 667570 4-Aug-2012 18:47 Send private message

Thanks MJB.

Unsure about the mail system configuration, it's the 'out-of-the-box' RaspberryPi ArchLinux image. Something else for this newby to learn about.

Will try the '|wall' pipe tomorrow (sports to watch and beer to drink tonight).

...and you're right, I must make more use of the manpages, although I don't find them all that 'beginner friendly'







808 posts

Ultimate Geek
+1 received by user: 78


  Reply # 667586 4-Aug-2012 19:33 Send private message

Decided to have a crack at it tonight, works a treat thank you.

Have learnt a bit now and I'll probably end up piping within the script rather than the crontab and using write instead of wall.





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