jq is insane

1st March 2025

I needed to modify JSON files, and the only language available in that container was Bash. Typically, I would look for a language such as Javascript or Python, as they are easier to write in, but there was no option. I had heard of jq before, but never looked at it properly as the syntax looked unapproachable. It took 15 minutes of reading docs, and experimenting but eventually got my desired output working. It looked something like this:

jq -r '[countries[].cities[].properties | select(population > 1000000) | .name] | join(",")' data.json

I'm sure it's only scratching the surface with what jq can do. The rough equivalent in Javascript would be:

import fs from "node:fs";

const data = fs.readFileSync("data.json", "utf8");
const countries = JSON.parse(data);

arr = [];
for (country in countries) {
  for (city in country) {
    if (city.properties.population > 1_000_000) {
      arr.push(city.properties.name);
    }
  }
}
output = arr.join(",");

Now when I need to query and modify JSON files, Bash with jq is my top choice.