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Old 12-24-2015, 05:22 AM   #1
Registered: Dec 2014
Posts: 197

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output to file not working

I am using mpg123 on raspbian to play mp3 files. I would like to create a log file showing which mp3 was played when. So I run this command in the terminal.

/usr/bin/mpg123 -Z /root/media/* 2>&1 | while read i; do echo "$(date): $i"; done | grep Playing
The output is this:
Thu Dec 24 12:17:36 EET 2015: Playing MPEG stream 2 of 5: test3.mp3 ...
Thu Dec 24 12:17:37 EET 2015: Playing MPEG stream 4 of 5: test5.mp3 ...
Thu Dec 24 12:17:39 EET 2015: Playing MPEG stream 3 of 5: test4.mp3 ...
Thu Dec 24 12:17:41 EET 2015: Playing MPEG stream 1 of 5: test2.mp3 ...
and its exactly what I want.

So now all I have to do is write this output to a file. To do that, I modify the command like this.

/usr/bin/mpg123 -Z /root/media/* 2>&1 | while read i; do echo "$(date): $i"; done | grep Playing >> /tmp/media.log
But all I get is an empty media.log file.

What I'm I doing wrong here?

Old 12-24-2015, 08:10 AM   #2
Registered: Feb 2009
Location: 192.168.x.x
Distribution: Slackware
Posts: 852

Rep: Reputation: 389Reputation: 389Reputation: 389Reputation: 389
How long have you let the code run before killing it?
I think the problem here is the large output buffer of grep. It will appear eventually, if you wait long enough to fill the output buffer. (Ctrl+C seems to kill the entire pipe without flushing it, though).
You can try running grep with the --line-buffered option and see if it helps.
Old 12-24-2015, 08:37 AM   #3
Registered: Dec 2014
Posts: 197

Original Poster
Rep: Reputation: 3
Thank you. --line-buffered resolved the issue.


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