how to add json value to json file using bash script

Question

Json file as follows:

{

      "ImageId": "ami-074acc26872f26463",
      "KeyName": "Accesskeypair",
      "SecurityGroupIds": ["sg-064caf9c470e4e8e6"],
      "InstanceType": ""
      "Placement": {
        "AvailabilityZone": "us-east-1a"
      }
}

read type #input from user

now i want to add json value in "InstanceType": "$type" in file using bash script i have tried sed, cat and echo

echo "Hello"
echo "lets create an instance"  
echo "please enter the type of instance you need"
read instance_type;
echo $type
 sed -a '|\InstanceType": "|$instance_type|a' awsspotinstancecreation.json
 sed -e '/\"InstanceType": "|$instance_type|/a' awsspotinstancecreation.json
 sed -i "/\InstanceType": "/ s/^\(.*\)\('\)/\1, $instance_type/" awsspotinstancecreation.json
 sed -e 's/^"InstanceType": "",.*$/"InstanceType": "$instance_type",/g' awsspotinstancecreation.json
 sed -i 's/^InstanceType .*$/"InstanceType": "$instance_type",/' awsspotinstancecreation.json
 sed -i 's:^"InstanceType": "",.*$:"InstanceType": "$instance_type",:a' awsspotinstancecreation.json

but when I do it comes "InstanceType": "$type" instead of "InstanceType": "t2.small"

Your file is invalid json. You're missing a comma after your InstanceType value. Like I said in the other thread, don't use sed, use jq — vintnes
– vintnes, Commented Jun 10, 2019 at 9:08

Shivam Seth · Accepted Answer · 2019-06-10 09:12:02Z

3

You can use light weight JSON processesor called jq

after loading your file you can use jq '.InstanceType = "This is instance value"

You can take reference from Add a new element to an existing JSON array using jq

edited Jun 10, 2019 at 9:12

answered Jun 10, 2019 at 9:05

Shivam Seth

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Vikash_Singh · Accepted Answer · 2019-06-10 09:52:58Z

2

use -e option will not modify the file instead it will print the output in terminal.

-i option will modify the file.

using .* regex will update the file and particular key having any value

and using \"\" will only look for empty string and update the value.

try this:

sed -i "s/\"InstanceType\":.*,$/\"InstanceType\": \"${instance_type}\",/g" awsspotinstancecreation.json

OR

sed -i "s/\"InstanceType\": \"\",$/\"InstanceType\": \"${instance_type}\",/g" awsspotinstancecreation.json

edited Jun 10, 2019 at 9:52

answered Jun 10, 2019 at 9:45

Vikash_Singh

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1 Comment

shrikkanth roxor Over a year ago

thanks a ton bro !!! it works perfectly and thanks for the explanation... means alot!

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