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 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.

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.