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What I want to do : at boot, start a playlist on a headless RBPi A+ through the headphones jack using mpg123.

I Wrote a shell script targeting mpg123:

#!/bin/bash
# see if (and when) my script was run : 
date >> /home/MY_USER_NAME/date.txt
# infinitely and randomly play a playlist using mpg123
/bin/mpg123 -v -o alsa --mono -Z 0 /home/MY_USER_NAME/music/lofi-grl/*.mp3

and added this line to crontab using sudo crontab -e : @reboot sh /home/MY_USER_NAME/start.sh >> ~/cron.log 2>&1

In short, the script is working fine from the terminal, but partially when run by cron : the file date.txt is there, but there is no sound, and if I do top | grep mpg123 there is no mpg123 process.

Everything in the cron.log file is fine except the last line :

000000+143478  00:00.00+01:02:27 --- 100=100  32 kb/s  104 B acc    0 clip p+0.000^M> 000008+143470  00:00.18+01:02:27 --- 100=100  32 kb/s  104 B acc    0 clip p+0.000
main: [src/mpg123.c:839] error: Deep trouble! Cannot flush to my output anymore!

I tried using crontab -e instead of sudo crontab -e, didn't work. I tried adding mpg123 to sudoers ALL ALL = NOPASSWD: /usr/bin/mpg123 to sudoers like suggested in an other thread but nothing works. I even tried using /etc/rc.local which didn't work either. I am really pulling my hair on this one ! Please help !

1 Answer 1

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I (finally) figured out : 1/ Although you can omit it when using the terminal it You have to specify which device you want mpg123 to use in the form -a hw:x,y when run from cron task (in my case hw:1,0 which is headphones jack output o, the RBPi)

2/ mpg123 can't operate until the sound device is ready (obviously) which is not the case when the @reboot event is fired. the solution was to wait for 20 seconds before running the script : @reboot sleep 20 && sh /path/to/myscript.sh

Now I have to figure out how to run this script exactly the moment the audio device is ready.

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  • "have to figure out how to run this script exactly the moment the audio device is ready". You won't be able to do that with cron - it's not "resource aware". You might be able to cobble a systemd unit, but be preared to spend time on this!
    – Seamus
    Commented Jan 18 at 20:28

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