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---
title: "jq is a powerful JSON processor"
date: 2021-06-13
categories: [ blog ]
tags: [unix, jq, json, cli, guide, tinker]
---
So lately I've been using `jq` quite a bit. It is a CLI JSON processor that
makes your life easier if you have to deal with a lot of JSON. Here I'm going
to give two examples of how it's used.
## Search response
I've been dealing with JSON from Elasticsearch API[^0], but as they would not
release their documents under a free license, I will take an example from
OpenSearch instead[^1]:
```json
{
"took": 39,
"timed_out": false,
"_shards": {
"total": 68,
"successful": 68,
"skipped": 0,
"failed": 0
},
"hits": {
"total": {
"value": 5837,
"relation": "eq"
},
"max_score": 7.8623476,
"hits": [
{
"_index": "new_shakespeare",
"_type": "_doc",
"_id": "100763",
"_score": 7.8623476,
"_source": {
"type": "line",
"line_id": 100764,
"play_name": "Troilus and Cressida",
"speech_number": 43,
"line_number": "3.1.68",
"speaker": "PANDARUS",
"text_entry": "Sweet queen, sweet queen! thats a sweet queen, i faith."
}
},
{
"_index": "shakespeare",
"_type": "_doc",
"_id": "28559",
"_score": 5.8923807,
"_source": {
"type": "line",
"line_id": 28560,
"play_name": "Cymbeline",
"speech_number": 20,
"line_number": "1.1.81",
"speaker": "QUEEN",
"text_entry": "No, be assured you shall not find me, daughter,"
}
}
]
}
}
```
Woah that's long!
How do you know how much time it took? I want to measure the performance.
```sh
$ curl ... | jq '.took'
39
```
Nice. Not very helpful, though---I can easily see that at the top of the
result. I want to see which responses were returned.
```sh
$ curl ... | jq '.hits.hits'
[
{
"_index": "new_shakespeare",
"_type": "_doc",
"_id": "100763",
"_score": 7.8623476,
"_source": {
"type": "line",
"line_id": 100764,
"play_name": "Troilus and Cressida",
"speech_number": 43,
"line_number": "3.1.68",
"speaker": "PANDARUS",
"text_entry": "Sweet queen, sweet queen! thats a sweet queen, i faith."
}
},
{
"_index": "shakespeare",
"_type": "_doc",
"_id": "28559",
"_score": 5.8923807,
"_source": {
"type": "line",
"line_id": 28560,
"play_name": "Cymbeline",
"speech_number": 20,
"line_number": "1.1.81",
"speaker": "QUEEN",
"text_entry": "No, be assured you shall not find me, daughter,"
}
}
]
```
The response is the value of `hits` inside a `hits`, so the query is
`.hits.hits`. How intuitive!
But this is hard to read. Let's just take the `play_name` of the result.
```sh
$ curl ... | jq .hits.hits[]._source.play_name
"Troilus and Cressida"
"Cymbeline"
```
Neat! But how does it work? The brackets `[]` signifies that we should take
all the results, from each of which the value for `._source.play_name` is
taken.
There might be the option to write that in the search query DSL, which also
reduces the data transferred, but I bet this is much easier to write.
## Wallpaper
I use `feh` for setting wallpaper, which can take an image from the internet.
Previously, I used a static list that I collected myself, but I recently
discovered a wallpaper API from [wallhaven](https://wallhaven.cc/help/api).
Let's say, I want to get a space image as wallpaper, I would use this command:
```sh
curl -s 'https://wallhaven.cc/api/v1/search?q=space&ratios=16x9&sorting=toplist'
```
Where `q` is the query, `ratios` is the image ratio so that it fits the screen,
and `sorting` is the way the results would be sorted before pagination. The
results is long, but it looks like this:
```json
{
"data": [
{
"id": "l3zmwy",
"url": "https://wallhaven.cc/w/l3zmwy",
"short_url": "https://whvn.cc/l3zmwy",
"views": 67050,
"favorites": 705,
"source": "https://www.artstation.com/artwork/YaQwgP",
"purity": "sfw",
"category": "general",
"dimension_x": 1920,
"dimension_y": 1080,
"resolution": "1920x1080",
"ratio": "1.78",
"file_size": 781731,
"file_type": "image/jpeg",
"created_at": "2021-05-18 19:26:23",
"colors": [
"#424153",
"#000000",
"#663300",
"#996633",
"#999999"
],
"path": "https://w.wallhaven.cc/full/l3/wallhaven-l3zmwy.jpg",
"thumbs": {
"large": "https://th.wallhaven.cc/lg/l3/l3zmwy.jpg",
"original": "https://th.wallhaven.cc/orig/l3/l3zmwy.jpg",
"small": "https://th.wallhaven.cc/small/l3/l3zmwy.jpg"
}
},
...
]
}
```
So, to get the image path from this, I run:
```sh
curl ... | jq -r .data[].path | shuf -n 1 | feh --bg-center
```
I use `shuf` because I'd like a new wallpaper every time I run this script.
Put this as the startup script or add a cron job and you'll have a changing
wallpaper. Disclaimer: this script does not always work, because of `feh`.
If you're using GNOME, for example, `feh` can't be used to set background.
[^0]: Yes I know it's no longer free software (it still partially is I think).
I have no choice, and I would still be more at peace with a source available
software that is self-hostable.
[^1]: Copyright 2021 OpenSearch contributors. Released under Apache License.
|
