how do I read multiple variables from a sub shell

Question

I've found similar problems on stackexchange, but never close enough to my case to help.

I'm trying to create a script and bind it to a key, so that when pressed, it displays "title by artist" OR, if there is no artist/title, it displays "filename".

Cmus (my music player of choice) has cmus-remote paired with the -C (raw) option which let me query cmus player for anything and get a newline-separated response like:

cmus-remote -C 'format_print %a %t %F'
Beach House
Space Song
/home/user/Music/Beach House - Space Song.mp3

The thing is, I don't want to run cmus-remote for each of the queries and instead would prefer

IFS= read -r artist title file << EOF
$(cmus-remote -C 'format_print %a %t %F')
EOF

However that only provides artist and title and file are empty Note: removing the -r option doesn't help in this case, nor does modifying IFS.

To elaborate: my Music folder isn't fully tagged, i.e. some songs don't have an artist or title, so the idea of this script is on exec to send a notification 'playing title by artist', if there's no title or artist 'playing filename' so I kindof need to have the three variables to then evaluate wich notification to send.

while yes, I do indeed use bash, i would prefer to have something more portable, though I will use bash if that's the more practical thing to do — Dr. Coomer, May 15 '23 at 12:18
Oh, oh, oh, sorry! Was that an answer? I thought you were just clarifying what you need. Answering your own question is not frowned upon _at all_. It is actually actively encouraged. This still doesn't make the variables survive after the `while` finishes, is that really all you need? If so, please let me know and I will udnelete your answer with my apologies. — terdon, May 15 '23 at 13:44
Fair enough. Sorry, @Dr.Coomer, my bad! I now rolled back my edit since it was I, not you, who was being dumb! — terdon, May 15 '23 at 13:47
Thanks folks! while I suppose having variables survive outside the loop might be nice, I don't exactly need it, a simple `if a and t else f` inside the loop is just fine for what I'm trying to do — Dr. Coomer, May 15 '23 at 14:37

score 0 · Answer 1 · edited May 15 '23 at 13:24

0

I just need a read for every newline, i.e.

cmus-remote -C 'format_print %a %t %F' | 
while IFS= read -r artist; IFS= read -r title; IFS= read -r file
do
  echo "a:$artist"
  echo "t:$title"
  echo "f:$file"
done

runs once and echoes the correct value, why IFS=$'\n' doesn't act like you'd think is beyond me, I'll accept three reads

edited May 15 '23 at 13:24

Kusalananda

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answered May 15 '23 at 13:14

Dr. Coomer

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how do I read multiple variables from a sub shell

1 Answers1