This is a text-only version of the following page on https://raymii.org:
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Title       :   Get a JSON value with bash and sed
Author      :   Remy van Elst
Date        :   26-02-2019
URL         :   https://raymii.org/s/snippets/Get_json_value_with_sed.html
Format      :   Markdown/HTML
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Recently I was asked to get one value from a json object using only shell tools.
The json in question is from a [dutch radio station][1] and it lists the current
song that is played. Using this together with a few shell commands and `notify-
send` we can show the current song when it changes as a desktop notification.
I'd rather use Python or `jq` if it has to be shell. In this case the co-worker
asked to just use simple shell tools and no external dependencies.

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This is the `json` file, formatted:



   # curl -s 'https://api.grootnieuwsradio.nl/playing.json'
   {
       "Stream_information":{
           "Name":"grootnieuws_ipad",
           "NameByClient":"grootnieuwsradio_website_aac",
           "Limit":"2000",
           "Account":"calculation",
           "IncomingSignal":"offline",
           "SecureTokenSharedSecret":"",
           "SecureTokenQueryParametersPrefix":"",
           "SecureTokenIncludeClientIPInHash":"false",
           "MultiBitrateEnable":"false",
           "DVREnable":"false",
           "PlayIPWhiteList":"",
           "PublishIPWhitelist":"",
           "SimultaneousConnections":"1729",
           "Auto_recording":"off",
           "PlayingNow":"Joke Buis - Welk Een Vriend Is Onze Jezus",
           "Encoder_visitors_statistics":{
               "REST_URI":"https:\/\/api.streampartner.nl\/grootnieuws_ipad\/stream_information\/encoder_visitors_statistics",
               "Options":[
                   "GET"
               ]
           }
       }
   }


The field we want is the `PlayingNow` field. Using `sed`, a regular expression
with a backreference (`\1`) it can be shown:



   sed -n 's|.*"PlayingNow":"\([^"]*\)".*|\1|p'


Example output:



   curl -s 'https://api.grootnieuwsradio.nl/playing.json' | sed -n 's|.*"PlayingNow":"\([^"]*\)".*|\1|p'

   Joke Buis - Welk Een Vriend Is Onze Jezus


The full script to send the desktop notifications:



   #!/bin/bash
   PATH="/usr/local/bin:/bin:/usr/bin:/sbin:/usr/sbin:/usr/local/bin:/usr/local/sbin:$PATH"
   if [[ ! -f /tmp/gnr-prev.txt ]]; then touch /tmp/gnr-prev.txt; fi
   PREVSONG="$(cat /tmp/gnr-prev.txt)"
   curl -s 'https://api.grootnieuwsradio.nl/playing.json' | sed -n 's|.*"PlayingNow":"\([^"]*\)".*|\1|p' > /tmp/gnr-cur.txt
   CURSONG="$(cat /tmp/gnr-cur.txt)"
   if [[ "$PREVSONG" != "$CURSONG" ]]; then
       mv /tmp/gnr-prev.txt /tmp/gnr.$(date +%s).txt;
       mv /tmp/gnr-cur.txt /tmp/gnr-prev.txt;
       notify-send "GNR: $CURSONG";
   fi


Put it in `cron` for regular execution. Add this to your crontab as well if you
use KDE:



   DISPLAY=:0.0
   XAUTHORITY=/home/remy/.Xauthority


Replace `remy` with your username.

  [1]: https://www.grootnieuwsradio.nl/
  [2]: https://www.digitalocean.com/?refcode=7435ae6b8212

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