Update values in json (array elements) using jq in loop

Question

I have a input json file with an array. I need to updated two values (ver & date) in each array element. I could come up with below script but need help. I have hardcoded the ver & date to simplify the script.

input.json

[
  {
    "svcname": "svc1",
    "repo": "https://repo.mycom.org/repocontext/svc1-list",
    "ver": "0.1",
    "date": "2019-11-05"
  },
  {
    "svcname": "svc1",
    "repo": "https://repo.mycom.org/repocontext/svc1-list",
    "ver": "0.1",
    "date": "2019-12-21"
  }
]

Script:

#!/bin/bash
set +x
injson=input.json
updatedjson=$(jq .[] ${injson})

services=$(cat ${injson} | jq '.[] | .svcname' | tr -d \")
i=1
for svc in $services; do 

        echo "==>$svc"
        echo "======> input json=${updatedjson}"
        echo "======> update ver=${i}"
        updatedjson=$(echo ${updatedjson} | jq ". | select( .name ==\"$svc\").ver=\"$i\"" | jq . )
        svcdate="2020-01-$i"
        echo "======> update date=$svcdate"
        updatedjson=$(echo ${updatedjson} | jq ". | select( .name ==\"$svc\").date=\"$svcdate\"" | jq . )
        echo "============================================"
        echo
        i=`expr $i + 1`

done

echo "======= write to file ====="
echo ${updatedjson}
echo ${updatedjson} | jq . > outjson.json

Inian · Accepted Answer · 2020-01-16 16:59:09Z

2

You are not using the true features of jq. What you shown in a loop, iterating over all the JSON objects can be simply reduced to one reduce() construct that is sort of a for loop in jq given an initial value and runs the filter incrementally

jq 'reduce range(0, length) as $d (.; (.[$d].ver = ($d+1|tostring)) | (.[$d].date = "2020-01-\($d+1)")) '

A brief explanation of how it works

The range expression returns a list with numbers generated from 0 to upto the length of the objects in the array. For your given input it produces 0,1 which is assigned to d
The reduce expression given the input value . the whole JSON, runs by setting the values in each object indexed by $d. So .[$d].ver refers to the ver field in the zeroth index. This is done incrementally till all the objects are processed.
The same way the date field is modified using [$d].date with the value string prefixed (YYYY-MM-) and date is set accordingly.

edited Jan 16, 2020 at 16:59

answered Jan 16, 2020 at 16:44

Inian

87k15 gold badges166 silver badges183 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

user3741611 Over a year ago

Now I am trying to use actual variables (in place of hardcoded values) but running into jq sytax error. === echo ${updatedjson} | jq "reduce range(0, length) as (.; (. | .[] | select( .name ==\"$svc\").version=\"$ver\") | (. | .[] | select( .name ==\"$svc\").date=\"$svcdate\")) " ==== & error is: ==== jq: error: syntax error, unexpected '(', expecting '$' or '[' or '{' (Unix shell quoting issues?) at <top-level>, line 1: ======

Collectives™ on Stack Overflow

Update values in json (array elements) using jq in loop

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related