paplay not working from cron

A little more than a year ago I wrote a notifier app. (on Ubuntu 16.04.7) which played some audio with paplay and then put up a yad window with the text of the notification. This could be run either from command line or from cron. Recently I installed Ubuntu 20.04.3 and found that running from command line still works but running from cron doesn't. I have a bin directory below my home directory where the script (remind.sh) is kept. The pared down version of remind.sh is the following. Note that when I run from cron I get no audio indication the script has run but the trace.txt file gets updated and yad produces a window.

#!/bin/bash
# reminder script called from either
#           1. cron or
#           2. directly from shell to pop-up or
#           3. gidday.sh
# produces a 'yad' window with a picture and message in it.

/usr/bin/paplay /home/gary/sounds/marimba.ogg

# trace the run
d=`date`
echo "done -- "$d >> trace.txt

# now put out the window
#
#/usr/bin/yad --borders=50 --scroll --image=/home/gary/Pictures/shrunk-pictures/${ar[$t]} --title="${ar[$t]}" --text-align=center --mouse --width=800 --height=400 --text='<span font="20">'"$txt"'</span>' 2>/dev/null

Sorry, I should have provided the following in my original post. The line in crontab that fires off the remind1.sh script is:

36 13 30 aug * export DISPLAY=:0 && export MESSG="get movies from lib" && /home/gary/bin/remind1.sh

As I said before, this all ran perfectly fine in Ubuntu 16.04. And it still doesn't explain why the paplay command doesn't run but the (uncommented) yad command does.

Solution 1:

Jobs run through cron, or systemd startup scripts aren't run in the same runtime environment that you have on your desktop. systemd startup scripts are run as root. None of your PATH changes, or other environment variable settings from your ~/.bashrc are automatically propagated to your cron job. For example, there's no $DISPLAY, so GUI programs need special treatment (read man xhost).

One can set environment variables for all one's cron jobs in the crontab file Read man 5 crontab.

Look at the results of echo "=== id ===";id;echo "=== set ===";set;echo "=== env ===";env | sort;echo "=== alias ===";alias in each of your environments.

Since the command part of the crontab line is, by default, interpreted by /bin/sh, which has a simpler syntax than /bin/bash, I recommend having command be a call to a bash script (executable, mounted, starts with #!/bin/bash) which sets up the environment, then calls the desired program.