Python script in bash with crontab doesn't work but without crontab it does

Question

I have a bash script taking a picture with my raspberry pi camera and measuring the humidity and temperature with a python script.

#!/bin/bash

raspistill -o /var/www/image.jpg -t 1000
python Adafruit_Python_DHT/examples/AdafruitDHT.py 2302 4 | tr -s ' ' | grep -o '[0-9]\+\.[0-9]\+' > /var/www/sensor.out

The bash script works if I execute it normally, but if I put it in crontab (as root) it still executes the first line but the second line returns an empty file. It removes but does not replace the old info.

pi@rpi ~ $ sudo crontab -e
 GNU nano 2.2.6                              File: /tmp/crontab.Y0eieF/crontab

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/home/pi


*/1 *  *   *   *     /home/pi/testcron.sh

I have no idea why it isn't working, is it maybe because of the named pipes?

Use the absolute path to the input file in the second line.

devnull
– devnull

2014-06-21 09:10:02 +00:00
Commented Jun 21, 2014 at 9:10 — devnull
– devnull, Commented Jun 21, 2014 at 9:10

CDahn · Accepted Answer · 2014-06-21 09:10:45Z

1

You have a relative path specified in your script, but you don't start in your home directory from the cronjob. Use absolute paths in your bash script.

answered Jun 21, 2014 at 9:10

CDahn

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2 Comments

CDahn Over a year ago

In general, the shell environment is pretty spartan inside a cronjob. You don't get your user's environment. Try running a "set" command redirected to a file as a cronjob to see what it looks like. This will help you tailor your scripts to work correctly.

user967587 Over a year ago

Oh I forgot about the path after trying to get cron working. Thanks for your help :)

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