[SOLVED] How to modify a JSON file in a for loop in a bash script?

Issue

I have a JSON file called data.json with the following content:

{
    "A": "10",
    "BB": {
    "m": "refresh",
    "t": 1100,
    "tt": 1,
    "pp": 0,
    "fp": 0
    },
    "ss": "1",
    "ZZZ": {
    "0": {
        "np": 45,
        "sh": "True",
        "ni": 32,
        "ft": "False",
        "te": "True",
        "t": 23,
        "mm": 21
    }
    },
    "nr": "564"
}

I want to a have bash script that does the following task. There is a for loop of i = 1 to 100 iterations. In the first iteration, only 0 in the value of "ZZZ" should be changed to the value of i which is 1. The new content should be written to data.json. In the second iteration, the content of data.json is read and only 1 in the value of "ZZZ" should be changed to the value of i which is 2 now and the new content should be written to data.json. This process executes to the end of the loop. I have the following script:

#!/bin/bash

# Input JSON file and output directory
input_file="data.json"

# Loop from i=1 to 100
for ((i=1; i<=100; i++)); do
    # Copy the original JSON to a new file
    cp "$input_file" "output.json"

    # Modify the JSON file with jq
    jq --argjson new_i "$i" '.ZZZ[$new_i] = .ZZZ[$i - 1] | del(.ZZZ[$i - 1])' "output.json" > "temp.json"

    # Move the modified JSON back to the original file
    mv "temp.json" "data.json"
done

When I run the script, I get the following error:

jq: 2 compile errors
jq: error: $i is not defined at <top-level>, line 1:
.ZZZ[$new_i] = .ZZZ[$i - 1] | del(.ZZZ[$i - 1]) 

My question is how to fix the error?

Thank you.

Solution

One way to achieve what you are looking for is as follows:

#!/bin/bash

for ((i=1; i<=100; i++)); do
    jq '.ZZZ = {
    '\"$i\"': {
        "np": 45,
        "sh": "True",
        "ni": 32,
        "ft": "False",
        "te": "True",
        "t": 23,
        "mm": 21
        }
    }' "data.json" > "temp.json"

    mv "temp.json" "data.json"
done

If you'd like to have distinct files after each write, you can change mv "temp.json" "data.json" to mv "temp.json" "data_$i.json"

Answered By - Bsh

Answer Checked By - Marie Seifert (WPSolving Admin)