[SOLVED] Problem with crontab in Mate

ewlabonte · 07-04-2019, 11:27 AM

I give up. This is beyond my abilities. For the life of me I can't figure out why this doesn't work with Debian but it does with other distros. But Debian is the best distro for this machine, so I'm just going to use Variety to change the wallpaper in Mate. I'm done. It will remain unsolved...

evo2 · 07-04-2019, 07:56 PM

Hi,

Quote:

Originally Posted by ewlabonte

Excellent idea. Crontab apparently called testwm which called materia, but I got no response on the desktop. If I call materia manually, it does change the wallpaper. But it didn't do that through crontab. Here's testwm.log:

Thu Jul 4 11:21:01 EDT 2019
DISPLAY is :0
x is 9667 ? 00:00:00 mate-session
y is
z is
Called /home/ewl/bin/materia
Done!

Ok, so now you know that /home/ewl/bin/materia is being run, it's time to debug that script.

Evo2.

ewlabonte · 07-04-2019, 08:03 PM

Quote:

Originally Posted by evo2

Hi,

Ok, so now you know that /home/ewl/bin/materia is being run, it's time to debug that script.

Evo2.

Here it is. But I don't see what there is to debug. It works fine when I run in a terminal.

#!/bin/sh
# Script to randomly set Background from files in a directory

# Directory Containing Pictures
DIR="/home/ewl/Pictures/Wallpapers"

# Command to Select a random jpg file from directory
# Delete the *.jpg to select any file but it may return a folder
PIC=$(ls $DIR/* | shuf -n1)

# Command to set Background Image
gsettings set org.mate.background picture-filename $PIC

evo2 · 07-04-2019, 08:40 PM

Hi,

the output from that script when run under from the modified /home/ewl/bin/testwm
should end up in /home/ewl/testwm.log. So how about /home/ewl/bin/materia

Code:

#!/bin/sh
# Script to randomly set Background from files in a directory
echo "This is $0"

# Directory Containing Pictures
DIR="/home/ewl/Pictures/Wallpapers"
echo "DIR is $DIR"

# Command to Select a random jpg file from directory
# Delete the *.jpg to select any file but it may return a folder
PIC=$(ls $DIR/* | shuf -n1)
echo PIC is $PIC

# Command to set Background Image
which gesttings
gsettings set org.mate.background picture-filename $PIC

If there is no output from the above echos etc. in the log file, then try explicitly redirecting to a log file in materia.

Evo2.

ewlabonte · 07-04-2019, 09:30 PM

Quote:

Originally Posted by evo2

Hi,

the output from that script when run under from the modified /home/ewl/bin/testwm
should end up in /home/ewl/testwm.log. So how about /home/ewl/bin/materia

If there is no output from the above echos etc. in the log file, then try explicitly redirecting to a log file in materia.

Evo2.

Thu Jul 4 22:28:01 EDT 2019
DISPLAY is :0
x is 1040 ? 00:00:00 mate-session
y is
z is
This is /home/ewl/bin/materia
DIR is /home/ewl/Pictures/Wallpapers
PIC is /home/ewl/Pictures/Wallpapers/city-wallpaper-12.jpg
/usr/bin/gsettings
Called /home/ewl/bin/materia
Done!

ewlabonte · 07-04-2019, 09:31 PM

Again materia was called but didn't change the wallpaper.

evo2 · 07-04-2019, 09:47 PM

Hi,

ok, next check the gsettings.... reading the gsettings man page...

Update the last few lines of your materia script to be

Code:

gsettings get org.mate.background picture-filename
echo "gettings return value was $?"
gsettings set org.mate.background picture-filename $PIC
echo "gettings return value was $?"
gsettings get org.mate.background picture-filename
echo "gettings return value was $?"

The if $? is not 0 then gsettings is reporting some sort of error.

Hmm, there seems to be an interesting "monitor" option. You could try running

Code:

gsettings monitor org.mate.background picture-filename

while the cron job executes.

Just keep digging.

Evo2.

ewlabonte · 07-05-2019, 10:27 AM

Quote:

Originally Posted by evo2

Hi,

ok, next check the gsettings.... reading the gsettings man page...

Update the last few lines of your materia script to be

The if $? is not 0 then gsettings is reporting some sort of error.

Hmm, there seems to be an interesting "monitor" option. You could try running

while the cron job executes.

Just keep digging.

Evo2.

Here's the testwm.log:

Fri Jul 5 11:24:01 EDT 2019
DISPLAY is :0
x is 1103 ? 00:00:00 mate-session
y is
z is
This is /home/ewl/bin/materia
DIR is /home/ewl/Pictures/Wallpapers
PIC is /home/ewl/Pictures/Wallpapers/moon-in-sky-3.jpg.jpg
'/home/ewl/Pictures/Wallpapers/variety-copied-wallpaper-92d9453b74067d549681e481924911ab.jpg'
gsettings return value was 0
gsettings return value was 0
'/home/ewl/Pictures/Wallpapers/moon-in-sky-3.jpg.jpg'
gsettings return value was 0
Called /home/ewl/bin/materia
Done!

the gsettings monitor command didn't produce any results.

ewlabonte · 07-06-2019, 03:34 PM

SOLVED IT!! I figured out that the problem was somehow with the gsettings command, so I googled "crontab gsettings" and got a link to https://askubuntu.com/questions/7428...ings-from-cron . Using what I got from this page I added

PID=$(pgrep mate-session)
export DBUS_SESSION_BUS_ADDRESS=$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$PID/environ|cut -d= -f2-)

to the beginning or the materia script, and it now changes the wallpaper. It all had to do with environment variables, or whatever. I'm too old to actually learn what all this means, but the script works in cron now. That's all that matters.

I want to thank all the people who helped me with this.

ewlabonte · 07-06-2019, 03:46 PM

Quote:

Originally Posted by kilgoretrout

Whenever I've run into this kind of problem, i.e. a script runs OK for the user but fails when called as a cron job, it invariably turned out to be due to the cron environment and the user environment having PATH differences. It's usually fixed by rewriting the script to have full absolute paths to all called locations and executables.

It turns out you were right, but I didn't know how to go about fixing the problem.