klp

![klp teaser][teaser]

:horse:klp (Kelpie) is a small, fast, and magical command-line data processor similar to pxi, jq, mlr, and awk.

[![node version][shield-node]][node]
[![npm version][shield-npm]][npm-package]
[![license][shield-license]][license]
[![PRs Welcome][shield-prs]][contribute]
[![linux unit tests status][shield-unit-tests-linux]][actions]
[![macos unit tests status][shield-unit-tests-macos]][actions]
[![windows unit tests status][shield-unit-tests-windows]][actions]

Installation

Installation is done using [npm][npm-install].

``bash
$ npm i -g klp
`

Try klp --help to see if the installation was successful.

Features

+ :penguin: Small: Kelpie [does one thing and does it well][unix-philosophy] (processing data with JavaScript).
+ :zap: Fast: klp is as fast as pxi and gawk, 3x faster than jq and mlr, and 15x faster than fx.
+ :sparkles: Magical: It is trivial to write your own ~~spells~~ plugins.
+ :smile_cat: Playful: Opt-in to more data formats by installing plugins.
+ :tada: Versatile: Use Ramda, Lodash and any other JavaScript library to process data on the command-line.
+ :heart: Loving: Pixie is made with love and encourages a positive and welcoming environment.

Getting Started

See the usage section below for more examples.

$3

For a quick start, read the following blog posts:

+ TODO

:horse: Kelpie

Kelpie's philosophy is to provide a small, extensible frame
for processing large files and streams with JavaScript functions.
Different data formats are supported through plugins.
JSON, CSV, SSV, and TSV are supported by default, but users can customize their Kelpie
installation by picking and choosing from more available (including third-party) plugins.

Kelpie works its magic by chunking, deserializing, applying functions, and serializing data.
Expressed in code, it works like this:

`javascript
function klp (data) { // Data is passed to klp from stdin.
const chunks = chunk(data) // The data is chunked into tokens
const jsons = deserialize(chunks) // The tokens are deserialized into JSON objects.
const jsons2 = transform(jsons) // Each JSON object is transformed to a different JSON object.
const string = serialize(jsons2) // The new JSON objects are serialized to a string.
process.stdout.write(string) // The string is written to stdout.
}
`

For example, chunking, deserializing, and serializing JSON is provided by the [klp-json][klp-json] plugin.

$3

The following plugins are available:

| | Chunkers | Deserializers | Appliers | Serializers | klp |
|----------------------------|-----------|----------------------------|----------------------------|----------------------------|:-----:|
| [klp-core][klp-core] | line | | map, flatMap, filter | string | ✓ |
| [klp-json][klp-json] | jsonObj | json | | json | ✓ |
| [klp-dsv][klp-dsv] | | csv, tsv, ssv, dsv | | csv, tsv, ssv, dsv | ✓ |
| [klp-sample][klp-sample] | sample | sample | sample | sample | ✕ |

The last column states which plugins come preinstalled in klp.
Refer to the .klp Module section to see how to enable more plugins and how to develop plugins.
New experimental pixie plugins are developed i.a. in the [klp-sandbox][klp-sandbox] repository.

$3

klp is very fast and beats several similar tools in [performance benchmarks][klp-benchmarks].
Times are given in CPU time (seconds), wall-clock times may deviate by ± 1s.
The benchmarks were run on a 13" MacBook Pro (2019) with a 2,8 GHz Quad-Core i7 and 16GB memory.
Feel free to run the [benchmarks][klp-benchmarks] on your own machine
and if you do, please [open an issue][issues] to report your results!

| [Benchmark][klp-benchmarks] | Description | klp | pxi | gawk | jq | mlr | fx |
|-----------------------------|-----------------------------------------------|------:|------:|-------:|-----:|------:|-----:|
| JSON 1 | Select an attribute on small JSON objects | 11s | 11s | 15s | 46s | – | 284s |
| JSON 2 | Select an attribute on large JSON objects | 20s | 20s | 20s | 97s | – | 301s |
| JSON 3 | Pick a single attribute on small JSON objects | 15s | 15s | 21s | 68s | 91s | 368s |
| JSON 4 | Pick a single attribute on large JSON objects | 26s | 26s | 27s | 130s | 257s† | 420s |
| JSON to CSV 1 | Convert a small JSON to CSV format | 15s | 15s | – | 77s | 60s | – |
| JSON to CSV 2 | Convert a large JSON to CSV format | 38s | 38s | – | 264s | 237s† | – |
| CSV 1 | Select a column from a small csv file | 11s | 11s | 8s | 37s | 23s | – |
| CSV 2 | Select a column from a large csv file | 19s | 19s | 9s | 66s | 72s | – |
| CSV to JSON 1 | Convert a small CSV to JSON format | 15s | 15s | – | – | 120s | – |
| CSV to JSON 2 | Convert a large CSV to JSON format | 42s | 42s | – | – | 352s | – |

† mlr appears to load the whole file instead of processing it in chunks if reading JSON.
This is why it fails on large input files.
So in these benchmarks, the first 20,000,000 lines are processed first, followed by the remaining 11,536,000 lines.
The times of both runs are summed up.

Usage

.klp Module

Users may extend and modify klp by providing a .klp module.
If you wish to do that, create a ~/.klp/index.js file and insert the following base structure:

`js
module.exports = {
plugins: [],
context: {},
defaults: {}
}
`

The following sections will walk you through all capabilities of .klp modules.
If you want to skip over the details and instead see sample code, visit [klp-klp][klp-klp]!

$3

You may write pixie plugins in ~/.klp/index.js.
Writing your own extensions is straightforward:

`js
const sampleChunker = {
name: 'sample',
desc: 'is a sample chunker.',
func: ({verbose}) => (data, prevLines, noMoreData) => (
// * Turn data into an array of chunks
// * Count lines for better error reporting throughout klp
// * Collect error reports: {msg: String, line: Number, info: String}
// If verbose > 0, include line in error reports
// If verbose > 1, include info in error reports
// * Return errors, chunks, lines, the last line, and all unchunked data
{err: [], chunks: [], lines: [], lastLine: 0, rest: ''}
)
}

const sampleDeserializer = {
name: 'sample',
desc: 'is a sample deserializer.',
func: ({verbose}) => (chunks, lines) => (
// * Deserialize chunks to jsons
// * Collect error reports: {msg: String, line: Number, info: Chunk}
// If verbose > 0, include line in error reports
// If verbose > 1, include info in error reports
// * Return errors and deserialized jsons
{err: [], jsons: []}
)
}

const sampleApplier = {
name: 'sample',
desc: 'is a sample applier.',
func: ({verbose}) => (jsons, lines) => (
// * Turn jsons into other jsons by applying all functions
// * Collect error reports: {msg: String, line: Number, info: Json}
// If verbose > 0, include line in error reports
// If verbose > 1, include info in error reports
// * Return errors and serialized string
{err: [], jsons: []}
)
}

const sampleSerializer = {
name: 'sample',
desc: 'is a sample serializer.',
func: ({verbose}) => jsons => (
// * Turn jsons into a string
// * Collect error reports: {msg: String, line: Number, info: Json}
// If verbose > 0, include line in error reports
// If verbose > 1, include info in error reports
// * Return errors and serialized string
{err: [], str: ''}
)
}
`

The name is used by Kelpie to select your extension,
the desc is displayed in the options section of klp --help, and
the func is called by Kelpie to transform data.

The sample extensions are bundled to the sample plugin, as follows:

`js
const sample = {
chunkers: [sampleChunker],
deserializers: [sampleDeserializer],
appliers: [sampleApplier],
serializers: [sampleSerializer]
}
`

$3

Plugins can come from two sources:
They are either written by the user, as shown in the previous section, or they are installed in ~/.klp/ as follows:

`bash
$ npm install klp-sample
`

If a plugin was installed, it has to be imported into ~/.klp/index.js:

`js
const sample = require('klp-sample')
`

Regardless of whether a plugin was defined by a user or installed from npm,
all plugins are added to the .klp module the same way:

`js
module.exports = {
plugins: [sample],
context: {},
defaults: {}
}
`

klp --help should now list the chunkers, deserializers, appliers and serializers of the sample plugin extensions
in their respective sections.

> :speak_no_evil: Adding plugins may break the klp command line tool!
> If this happens, just remove the plugin from the list and klp should work normal again.
> Use this feature responsibly.

$3

Libraries like [Ramda][ramda] and [Lodash][lodash] are of immense help when writing functions to transform JSON objects
and many heated discussions have been had, which of these libraries is superior.
Since different people have different preferences, pixie lets the user decide which library to use.

First, install your preferred libraries in ~/.klp/:

`bash
$ npm install ramda
$ npm install lodash
`

Next, add the libraries to ~/.klp/index.js:

`js
const R = require('ramda')
const L = require('lodash')

module.exports = {
plugins: [],
context: Object.assign({}, R, {_: L}),
defaults: {}
}
`

You may now use all Ramda functions without prefix, and all Lodash functions with prefix _:

`bash
$ klp --with map "prop('time')" < 2019.jsonl
$ klp --with map "json => _.get(json, 'time')" < 2019.jsonl
`

> :hear_no_evil: Using Ramda and Lodash in your functions may have a negative impact on performance!
> Use this feature responsibly.

$3

Just as you may extend Kelpie with third-party libraries like Ramda and Lodash,
you may add your own functions.
This is as simple as adding them to the context in ~/.klp/index.js:

`js
const getTime = json => json.time

module.exports = {
plugins: [],
context: {getTime},
defaults: {}
}
`

After adding it to the context, you may use your function:

`bash
$ klp --with map "json => getTime(json)" < 2019.jsonl
$ klp --with map "getTime" < 2019.jsonl
`

$3

You may globally change default chunkers, deserializers, appliers, and serializers in ~/.klp/index.js, as follows:

`js
module.exports = {
plugins: [],
context: {},
defaults: {
chunker: 'sample',
deserializer: 'sample',
appliers: 'sample',
serializer: 'sample',
noPlugins: false
}
}
`

> :see_no_evil: Defaults are assigned globally and changing them may break existing klp scripts!
> Use this feature responsibly.

id Plugin

klp includes the [id][klp-id] plugin that comes with the following extensions:

| | Description |
|-------------------|----------------------------------------------------------------------------|
| id chunker | Returns each data as a chunk. |
| id deserializer | Returns all chunks unchanged. |
| id applier | Does not apply any functions and returns the JSON objects unchanged. |
| id serializer | Applies Object.prototype.toString to the input and joins without newlines. |

Comparison to Related Tools

| | [klp][klp]/[pxi][pxi] | [jq][jq] | [mlr][mlr] | [fx][fx] | [gawk][gawk] |
|-------------------------|-------------------------------------------------------------------------------------|--------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Self-description | Small, fast, and magical command-line data processor similar to awk, jq, and mlr. | Command-line JSON processor | Miller is like awk, sed, cut, join, and sort for name-indexed data such as CSV, TSV, and tabular JSON | Command-line tool and terminal JSON viewer | The awk utility interprets a special-purpose programming language that makes it possible to handle simple data-reformatting jobs with just a few lines of code |
| Focus | Transforming data with user provided functions and converting between formats | Transforming JSON with user provided functions | Transforming CSV with user provided functions and converting between formats | Transforming JSON with user provided functions | Language for simple data reformatting tasks |
| License | [MIT][license] | [MIT][jq-license] | [BSD-3-Clause][mlr-license] | [MIT][fx-license] | [GPL-3.0-only][gawk-license] |
| Performance | (performance is given relative to klp/pxi) | jq is >3x slower than klp | mlr is >3x slower than klp | fx is >15x slower than klp | klp is as performant as gawk when processing JSON and CSV |
| Processing Language | JavaScript and all [JavaScript libraries][npm] | [jq language][jq-lang] | [Predefined verbs and custom put/filter DSL][mlr-verbs] | JavaScript and all [JavaScript libraries][npm] | [awk language][gawk-lang] |
| Extensibility | (Third-party) Plugins, any [JavaScript library][npm], custom functions | (Third-party) [Modules][jq-modules] written in [jq][jq-lang] | Running arbitrary [shell commands][mlr-shell] | Any [JavaScript library][npm], custom functions | [gawk dynamic extensions][gawk-extensions] |
| Similarities | | klp and jq both heavily rely on JSON | klp and mlr both convert back and forth between CSV and JSON | klp and fx both apply JavaScript functions to JSON streams | klp and gawk both transform data |
| Differences | | klp and jq use different processing languages | While klp uses a programming language for data processing, mlr uses a custom put/filter DSL, also, mlr reads in the whole file while klp processes it in chunks | klp supports data formats other than JSON, and fx provides a terminal JSON viewer | While klp functions transform a JSON into another JSON, gawk does not have a strict format other than transforming strings into other strings |

Reporting Issues

Please report issues [in the tracker][issues]!

Contributing

We are open to, and grateful for, any contributions made by the community.
By contributing to pixie, you agree to abide by the [code of conduct][code].
Please read the [contributing guide][contribute].

License

klp` is [MIT licensed][license].

[actions]: https://github.com/Yord/klp/actions
[code]: https://github.com/Yord/klp/blob/master/CODE_OF_CONDUCT.md
[contribute]: https://github.com/Yord/klp/blob/master/CONTRIBUTING.md
[fx]: https://github.com/antonmedv/fx
[fx-license]: https://github.com/antonmedv/fx/blob/master/LICENSE
[gawk]: https://www.gnu.org/software/gawk/
[gawk-extensions]: https://www.gnu.org/software/gawk/manual/gawk.html#Dynamic-Extensions
[gawk-lang]: https://www.gnu.org/software/gawk/manual/gawk.html
[gawk-license]: https://www.gnu.org/software/gawk/manual/gawk.html#GNU-General-Public-License
[issues]: https://github.com/Yord/klp/issues
[jq]: https://github.com/stedolan/jq
[jq-lang]: https://github.com/stedolan/jq/wiki/jq-Language-Description
[jq-license]: https://github.com/stedolan/jq/blob/master/COPYING
[jq-modules]: https://stedolan.github.io/jq/manual/#Modules
[license]: https://github.com/Yord/klp/blob/master/LICENSE
[lodash]: https://lodash.com/
[mlr]: https://github.com/johnkerl/miller
[mlr-license]: https://github.com/johnkerl/miller/blob/master/LICENSE.txt
[mlr-shell]: http://johnkerl.org/miller/doc/data-sharing.html#Running_shell_commands
[mlr-verbs]: http://johnkerl.org/miller/doc/reference-verbs.html
[node]: https://nodejs.org/
[npm]: https://www.npmjs.com
[npm-install]: https://docs.npmjs.com/downloading-and-installing-packages-globally
[npm-package]: https://www.npmjs.com/package/klp
[klp]: https://github.com/Yord/klp
[klp-core]: https://github.com/Yord/klp-core
[klp-benchmarks]: https://github.com/Yord/klp-benchmarks
[klp-dsv]: https://github.com/Yord/klp-dsv
[klp-id]: https://github.com/Yord/klp/tree/master/src/plugins/id
[klp-json]: https://github.com/Yord/klp-json
[klp-module]: https://github.com/Yord/klp#klp-module
[klp-klp]: https://github.com/Yord/klp-klp
[klp-sample]: https://github.com/Yord/klp-sample
[klp-sandbox]: https://github.com/Yord/klp-sandbox
[ramda]: https://ramdajs.com/
[shield-license]: https://img.shields.io/npm/l/klp?color=yellow&labelColor=313A42
[shield-node]: https://img.shields.io/node/v/klp?color=red&labelColor=313A42
[shield-npm]: https://img.shields.io/npm/v/klp.svg?color=orange&labelColor=313A42
[shield-prs]: https://img.shields.io/badge/PRs-welcome-green.svg?labelColor=313A42
[shield-unit-tests-linux]: https://github.com/Yord/klp/workflows/linux/badge.svg?branch=master
[shield-unit-tests-macos]: https://github.com/Yord/klp/workflows/macos/badge.svg?branch=master
[shield-unit-tests-windows]: https://github.com/Yord/klp/workflows/windows/badge.svg?branch=master
[teaser]: https://github.com/Yord/klp/blob/master/teaser.gif?raw=true
[unix-philosophy]: https://en.wikipedia.org/wiki/Unix_philosophy