Play with JQ

#!/bin/bash

# Visit and share my telegram channel with your friends: http://t.me/linuxcheatsheet

# Run this code on your local computer: you can't use external tools like jq on glot.io

# And don't forget to install jq to use this script!

# yum install jq or apt-get install jq or pacman -S jq or whatever your distro use for packages!

# The json example was taken from:

# https://github.com/LearnWebCode/json-example/blob/master/animals-1.json

# For the purpose of this exercise, I will generate a sample json on the fly

# and save it to a tmpfile.

which jq 2> /dev/null &> /dev/null

if ( [ $? -ne 0 ] ); then echo "You must install jq to use the script!"; exit 0; fi

TMPJSON=$(mktemp)

cat << EOF > $TMPJSON

[

{

"name": "Meowsy",

"species" : "cat",

"foods": {

"likes": ["tuna", "catnip"],

"dislikes": ["ham", "zucchini"]

}

},

{

"name": "Barky",

"species" : "dog",

"foods": {

"likes": ["bones", "carrots"],

"dislikes": ["tuna"]

}

},

{

"name": "Purrpaws",

"species" : "cat",

"foods": {

"likes": ["mice"],

"dislikes": ["cookies"]

}

}

]

EOF

# First filter you need to know: the 'dot' filter. It does nothing to your json but output it again

echo "Using dot filter"

sleep 2

jq . $TMPJSON

echo "Press any key to continue..."

read -sN1

echo "You can use dot filter to check if a json if valid"

jq . $TMPJSON 2> /dev/null &> /dev/null

if ( [ $? -eq 0 ] ); then echo "*** Valid json [OK]"; else echo "*** Broken Json [ERROR]"; fi

echo "Press any key to continue..."

read -sN1

echo "Let's skip a line in our example json to break it on purpose"

tail +2 $TMPJSON | jq . 2> /dev/null &> /dev/null

if ( [ $? -eq 0 ] ); then echo "*** Valid json [OK]"; else echo "*** Broken Json [ERROR]"; fi

echo "Press any key to continue..."

read -sN1

# .[] extract all elements in the json array between [ and ]

# then I combine (pipe sign) it with the "select" filter.

# I will select all the objects where the json key named species equals cat

echo "I love cats ;-) let's select its from our json"

jq '.[] | select(.species == "cat")' $TMPJSON

echo "Press any key to continue..."

read -sN1

# You can of course combine multiple filters.

# Depending on the structure of the json, you can extract some keys

# like the names of all cats in the example

echo "What are its names?"

jq '.[] | select(.species == "cat") | .name' $TMPJSON

echo "That's all for this small example!"

echo "I hope you found this useful! Visit and share my telegram channel with your friends: http://t.me/linuxcheatsheet"

[ -f $TMPJSON ] && rm -f $TMPJSON

exit 0