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I wrote a .jar file that is supposed to be run once a day that interacts with Google App Engine. When I run it from the computer, it runs just fine and creates a logfile that details some statistics. I transferred it over to the Raspberry Pi and it runs via crontab.

The first time I ran it, I got a permission denied in syslog. I read that using 'sudo crontab -e' would fix that. Now I no longer get the error but my logfile doesn't appear.

Here is the portion of the code that is to create the logfile:

        PrintWriter writer = new PrintWriter("log" + format.format(date) + ".txt");
        writer.println("Total Themes: " + numThemes + "\r\n");
        writer.println("Active Themes: " + numActiveThemes + "\r\n");
        writer.println("Inactive Themes: " + numInactiveThemes + "\r\n");
        writer.println("Total Sales: " + numSales + "\r\n");
        writer.println("Total Price Changes: " + numPriceChanges + "\r\n");
        writer.println("Total Time: " + seconds + " seconds" + "\r\n");
        writer.close();

Crontab:

0 2 * * * java -jar /mnt/data/scripts/test.jar

What am I missing about the switch from Windows that is preventing the creation of the logfile?

Edit: I can run the .jar file manually (using sudo) and the logfile is created. Not working w/cron though.

Edit2: /etc/log/syslog has:

Feb  8 21:46:01 raspberrypi /USR/SBIN/CRON[10841]: (root) CMD (java -jar /mnt/data/scripts/updater_pricing.jar

Edit 3: Changed permissions of the folder and jar to 777 (as a test). Now I can run the file w/o 'sudo' (expected). Tried running a regular cron task using the same cron expression as above. Now syslog has: 

Feb  9 07:55:01 raspberrypi /USR/SBIN/CRON[13292]: (pi) CMD (/usr/bin/java -jar /mnt/data/scripts/test.jar)

It also has: Feb 9 07:55:59 raspberrypi /USR/SBIN/CRON[13291]: (CRON) info (No MTA installed, discarding output)

Perhaps I can add something that will output the error message?

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  • What user is running the cronjob and do they have permissions to write in the given directory?
    – Jacobm001
    Feb 9, 2015 at 4:05
  • How do I find out what user? I logged in via the default user "pi" via ssh and did 'sudo crontab -e' I tried changing the permissions of the folder 'scripts' to 777 but appear to get the same result.
    – easycheese
    Feb 9, 2015 at 4:07
  • Running crontab under sudo can do some strange things... Does the command need root privileges? If not try removing it from that file and run 'crontab -e'. This will run under the user "pi" and may be less error prone.
    – Jacobm001
    Feb 9, 2015 at 4:41
  • It needs to create a file, doesn't that need sudo permissions?
    – easycheese
    Feb 9, 2015 at 12:13
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    crontab sends errors through your system's mail client. I would suggest installing postfix and configuring it with the smtp service of whatever you use as an email client. Example: rtcamp.com/tutorials/linux/ubuntu-postfix-gmail-smtp try that and let us know what error you're getting.
    – Jacobm001
    Feb 9, 2015 at 16:04

1 Answer 1

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Figured it out thanks to the pointers from @Jacobm001. The email was being sent because I had some lines of System.out.println()

The logfiles were being created, just in the wrong place. I had to modify the original file line to be:

PrintWriter writer = new PrintWriter("/mnt/data/scripts/" + "log" + format.format(date) + ".txt");
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  • 1
    Congrats, glad to hear you got it working!
    – Jacobm001
    Feb 11, 2015 at 0:52

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