I've managed to flatten JSON files effortlessly by executing this command in a combination of Node.js and Bash:
npx flat foo.json > bar-flat-output.jsonBut now, I'm searching for another foolproof command that can easily undo the flattening process and restore my JSON files to their original structure.
If you're searching for a command to flatten and unflatten JSON in bash, you don't have to limit yourself to just npx flat. There are alternative solutions available, such as using jq.
Let me explain the differences between two versions:
{
"key1": { "keyA": "valueI" },
"key2": { "keyB": 2 },
"key3": { "a": { "b": { "c": 2 } } },
"key4": [1,[2,[3,4],5],6],
"key5": true
}
FLATTENED=$(jq '[ . as $json | paths(scalars) | . as $path | [., ($json | getpath($path))] ]' <<< "$INPUT")
[
[["key1","keyA"],"valueI"],
[["key2","keyB"],2],
[["key3","a","b","c"],2],
[["key4",0],1],
[["key4",1,0],2],
[["key4",1,1,0],3],
[["key4",1,1,1],4],
[["key4",1,2],5],
[["key4",2],6],
[["key5"],true]
]
jq 'reduce .[] as $x (null; setpath($x[0]; $x[1]))' <<< "$FLATTENED"
{
"key1": { "keyA": "valueI" },
"key2": { "keyB": 2 },
"key3": { "a": { "b": { "c": 2 } } },
"key4": [1,[2,[3,4],5],6],
"key5": true
}
FLATTENED=$(jq '
def key: map(if type == "number" then "[\(tostring)]" else . end) | join(".");
[ . as $json | paths(scalars) | . as $path | [key, ($json | getpath($path))] ]
| reduce .[] as $x ({}; .[$x[0]] = $x[1])
' <<< "$INPUT")
{
"key1.keyA": "valueI",
"key2.keyB": 2,
"key3.a.b.c": 2,
"key4.[0]": 1,
"key4.[1].[0]": 2,
"key4.[1].[1].[0]": 3,
"key4.[1].[1].[1]": 4,
"key4.[1].[2]": 5,
"key4.[2]": 6,
"key5": true
}
jq '
to_entries
| map(.key |= (split(".") | map(if test("^\\[[0-9]+\\]$"; "") then .[1:-1] | tonumber else . end)))
| reduce .[] as $x (null; setpath($x.key; $x.value))
' <<< "$FLATTENED"
{
"key1": { "keyA": "valueI" },
"key2": { "keyB": 2 },
"key3": { "a": { "b": { "c": 2 } } },
"key4": [1,[2,[3,4],5],6],
"key5": true
}
jqg is a Bash script called jqg that can flatten and unflatten JSON data using the tool jq.
Here's an example of how it works with randomly generated JSON:
{
"dicit": [
"periculis commune temporibus eripuit",
"potenti timeam venenatis an",
292,
"dissentias class nostrud duis",
906.641
],
"vestibulum": true,
"veritus": [
"consequat rationibus assueverit tota mnesarchum",
"eligendi lobortis",
false,
"prodesset mauris accusam vivendum vel",
"vero lacinia"
],
"purus": {
"ubique": "inciderint",
"errem": "malesuada solet suspendisse dissentiet",
"ridens": "regione",
"omnes": {
"dolorem": true,
"repudiare": -118,
"errem": [
false,
891.375,
"dicta feugiat pede accusamus odio",
"nobis",
"vehicula option aperiam",
"massa"
]
}
},
"facilisi": 565
}
After using jqg with the command $ jqg . /tmp/rnd.json, the JSON is flattened to:
{
"dicit.0": "periculis commune temporibus eripuit",
"dicit.1": "potenti timeam venenatis an",
"dicit.2": 292,
"dicit.3": "dissentias class nostrud duis",
"dicit.4": 906.641,
"vestibulum": true,
"veritus.0": "consequat rationibus assueverit tota mnesarchum",
"veritus.1": "eligendi lobortis",
"veritus.2": false,
"veritus.3": "prodesset mauris accusam vivendum vel",
"veritus.4": "vero lacinia",
"purus.ubique": "inciderint",
"purus.errem": "malesuada solet suspendisse dissentiet",
"purus.ridens": "regione",
"purus.omnes.dolorem": true,
"purus.omnes.repudiare": -118,
"purus.omnes.errem.0": false,
"purus.omnes.errem.1": 891.375,
"purus.omnes.errem.2": "dicta feugiat pede accusamus odio",
"purus.omnes.errem.3": "nobis",
"purus.omnes.errem.4": "vehicula option aperiam",
"purus.omnes.errem.5": "massa",
"facilisi": 565
}
Additionally, jqg can filter the flattened JSON by using the command $ jqg errem /tmp/rnd.json:
{
"purus.errem": "malesuada solet suspendisse dissentiet",
"purus.omnes.errem.0": false,
"purus.omnes.errem.1": 891.375,
"purus.omnes.errem.2": "dicta feugiat pede accusamus odio",
"purus.omnes.errem.3": "nobis",
"purus.omnes.errem.4": "vehicula option aperiam",
"purus.omnes.errem.5": "massa"
}
If you want to unflatten the filtered JSON, simply use
$ jqg errem /tmp/rnd.json | jqg -u{
"purus": {
"errem": "malesuada solet suspendisse dissentiet",
"omnes": {
"errem": [
false,
891.375,
"dicta feugiat pede accusamus odio",
"nobis",
"vehicula option aperiam",
"massa"
]
}
}
}
Please note that I am the creator of this useful tool called jqg.
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