Print output not shown when run Python script CRON

Question

I am automatically running a simple python program from start up using cron. The pi boots / automatically logs in, displays the command line and runs the python program but the print output (updating count) is not displayed.

The print output works fine if I run the program via idle (ie having enabled LXDE) and it also works fine if (without running the LXDE desktop) I manually run the program from the command line, e.g. sudo python pimon.py

What is needed to see the print output when I start the program using cron? I do not want to have to enable the LXDE desktop first.

The crontab entry is: @reboot python /home/pi/Python27/pimon.py

• mazianni: Please show your crontab entry.
• Ghanima: Your script run by cron simply has no console to print its output too. The behaviour you describe is perfectly normal. Best way to work around: make your script output to a file.
• joan: Where have you told the output to go? A cron job is not started from a terminal so is not attached to a keyboard or screen. Perhaps you need to redirect the output to a file.
• Ghanima: See also: raspberrypi.stackexchange.com/questions/40493/…

Answer 1

As others have noted in the comments, you need to redirect the output from the command somewhere.

This will write to a file, overwriting the file if it already exists.

@reboot python /home/pi/Python27/pimon.py > /path/to/output_file.txt

Change> to>> if you want to append to an existing file.

Check this link for more information on standard input and output redirection.

• Ghanima: Please note that the ampersand is not necessary since cron already forks the program.