Parse a variant array using command line utils in bash

Question

To get the current song being played in spotify (using DBus), I use the following command:

dbus-send --print-reply --session --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.freedesktop.DBus.Properties.Get string:'org.mpris.MediaPlayer2.Player' string:'Metadata'

Now, the output of the command below is like: (stripped down for clarity)

variant       array [
     dict entry(
        string "xesam:artist"
        variant                array [
              string "The Black Keys"
           ]
     )

     dict entry(
        string "xesam:title"
        variant                string "Give Your Heart Away"
     )
     ]

The output is a bit long & I want to parse specific values from it like title, artist etc.

Googling said that variant a popular datatype used in Component Object Model so I get there is a better way than using sed/awk to get the values. So, how do I go about doing this?

Rather than trying to parse this yourself, it might make more sense to use a dbus client library, for example the dbus module in python. — FatalError
– FatalError, Commented Jan 30, 2012 at 2:51
I felt that it's an overkill to do it that way because I just want to know the current song being played. — shadyabhi
– shadyabhi, Commented Jan 30, 2012 at 2:56
@AbhijeetRastogi It's almost never overkill to use a library that speaks the protocol which is being spoken to you, rather than using a text hack. If you do it wrong, it will break. — Borealid
– Borealid, Commented Jan 30, 2012 at 2:58

shellter · Accepted Answer · 2012-01-30 03:52:23Z

Try this

awk '
  /string  *"xesam:artist/{
    while (1) {
      getline line
      if (line ~ /string "/){
        sub(/.*string "/, "artist:", line)
        sub(/".*$/, "", line)
        print line
        break
      }
    }
  }
  /string  *"xesam:title/{
    while (1) {
      getline line
      if (line ~ /string "/){
        sub(/.*string "/, "title:", line)
        sub(/".*$/, "", line)
        print line
        break
      }
    }
  }
'  variantArraySample.txt

Gives output

artist:The Black Keys
title:Give Your Heart Away

This assumes that there will always be at least 1 line difference between the input, i.e.

    string "xesam:title"
    variant                string "Give Your Heart Away"

That is to say, if your data is all rolled up into one line, then it will require further logic, so

    string "xesam:title" variant string "Give Your Heart Away"

(for example), would require changes to the above script.

Let me know if you need help formatting the output further for your need.

I hope this helps.

SiegeX · Accepted Answer · 2012-01-30 06:37:26Z

1

The following works regardless what order 'title' or 'artist' come in. The only restriction is that after it sees :title, the next line containing string must be the title string; it doesn't matter how far away that line is though. Likewise for the artist

awk '
/:artist/{a=1;next}
/:title/{t=1;next}
a && /string/{
  sub(/^.*string /,"")
  artist=$0
  a=0; next
}
t && /string/{
  sub(/^.*string /,"")
  title=$0
  t=0;next
}
END{
  printf("artist:%s\n title:%s\n", artist,title)
}'

Output

artist:"The Black Keys"
 title:"Give Your Heart Away"

answered Jan 30, 2012 at 6:37

SiegeX

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