Extract title and message from the output of dbus-monitor

Question

I'm writing a bash script that executes a command every time a notification is triggered from the system and I'm using the output of dbus-monitor "interface='org.freedesktop.Notifications'".

I'm struggling to extract only title and message from the output of that command, could you please help me to do that?

I tried to do:

dbus-monitor "interface='org.freedesktop.Notifications'" |
  grep --line-buffered "string" |
  grep --line-buffered -e method -e ":" -e '""' -e urgency -e notify -v |
  grep --line-buffered '.*(?=string)|(?<=string).*' -oPi |
  grep --line-buffered -v '^\s*$' |
  grep --line-buffered -wvi 'image-data\|variant\|desktop-entry\|activate\|default\|sender-pid' |
  while read -r LINE; do
      printf "$LINE\n\n"
      # ...other commands...
  done

and it prints something like:

"Firefox"
"<message from Firefox>"
"Firefox"
"Firefox"
// ...

so that's not exactly what I want to accomplish!

Any help is appreciated!

Thanks

edit:

example of the dbus-monitor:

signal time=1668013439.676960 sender=org.freedesktop.DBus -> destination=:1.1820 serial=4294967295 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=NameLost
   string ":1.1820"
method call time=1668013457.635273 sender=:1.131 -> destination=:1.56 serial=704 path=/org/freedesktop/Notifications; interface=org.freedesktop.Notifications; member=Notify
   string "Firefox"
   uint32 0
   string ""
   string "<message1>"
   string "<message2>"
   array [
      string "default"
      string "Activate"
   ]
   array [
      dict entry(
         string "desktop-entry"
         variant             string "Firefox"
      )
      dict entry(
         string "image-data"
         variant             struct {
               int32 48
               int32 48
               int32 192
               boolean true
               int32 8
               int32 4
               array of bytes [
                  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                  ...
               ]
            }
      )
   ]
   int32 -1

I'd like to extract:

Title: "Firefox"
Message: <message1>, <message2>
Time: <date of receiving>

Answer 1

You could use GNU awk for this task:

dbus-monitor "interface='org.freedesktop.Notifications'" |
awk '
    $1 == "signal" {
        if (state) emit()
        state = 0
        _title = ""
        _messages = ""
        split($2,arr,"=")
        _date = strftime("%Y-%m-%dT%H:%M:%S%z",arr[2])

        next
    }
    $1 == "method" { state = 1; next; }
    $1 == "string" && (state == 1 || state == 2) && match($0,/".+"/) {
        s = substr($0,RSTART,RLENGTH)
        if (state == 1) {
            _title = s
            state = 2
            next
        } else
            _messages = (_messages == "" ? "" : _messages ", ") s
    }
    $1 == "array" { state = 3 }
    END { if (state) emit() }
    function emit() {
        print "Title:", _title
        print "Message:", _messages
        print "Date: " _date
        fflush()
    }
'

^{remark: the input format isn't clear to me so the current state machine might be inaccurate; it works with the example though}

Title: "Firefox"
Message: "<message1>", "<message2>"
Date: 2022-11-09T12:03:59-0500