babashka/README.md

# babashka

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A pure, fast and (severely!) limited version of Clojure in Clojure for shell scripting.

Properties:

- pure (no side effects)
- fast startup time
- interprets only one form
- reads from stdin and writes to stdout

## Rationale

Most of your script is in bash, but you want a tiny sprinkle of Clojure.

If most of your shell script evolves into Clojure, you might want to turn to:

- [planck](https://planck-repl.org/)
- [joker](https://github.com/candid82/joker)
- [lumo](https://github.com/anmonteiro/lumo)

## Status

Experimental. Breaking changes are expected to happen at this phase. Not all
Clojure core functions are supported yet, but can be easily
[added](https://github.com/borkdude/babashka/blob/master/src/babashka/interpreter.clj#L10). PRs
welcome.

## Installation

Linux and macOS binaries are provided via brew.

Install:

    brew install borkdude/brew/babashka

Upgrade:

    brew upgrade babashka

You may also download a binary from [Github](https://github.com/borkdude/babashka/releases).

## Usage

``` shellsession
... | bb [--raw] '<Clojure form>'
```

There is one special variable, `*in*`, which is the input read from stdin. When
the `--raw` flag is provided, `*in*` is a single string or vector of
strings. When it is omitted, the input is read as EDN.

The current version can be printed with:

``` shellsession
bb --version
0.0.2
```

Examples:

``` shellsession
$ ls | bb --raw '*in*'
["LICENSE" "README.md" "bb" "doc" "pom.xml" "project.clj" "reflection.json" "resources" "script" "src" "target" "test"]

$ ls | bb --raw '(count *in*)'
11

$ echo '[1 1 1 1 2]' | bb '(vec (dedupe *in*))'
[1 2]

$ echo '[{:foo 1} {:bar 2}]' | bb '(filter :foo *in*)'
({:foo 1})
```

Functions are written using the reader tag `#f`. Currently up to three
arguments are supported.

``` shellsession
$ echo '3' | bb '(#f(+ %1 %2 %3) 1 2 *in*)'
6
```

Regexes are written using the reader tag `#r`.

``` shellsession
$ ls | bb --raw '(filterv #f(re-find #r "reflection" %) *in*)'
["reflection.json"]
```

Find the line numbers where the word Clojure occurs using a case insensitive regex:

``` shellsession
$ cat /tmp/test.txt
foo
Clojure is nice
bar
when you're nice to clojure

$ cat /tmp/test.txt | bb --raw '(map-indexed #f[%1 %2] *in*))' | \
bb '(keep #f(when (re-find #r"(?i)clojure" (second %)) (first %)) *in*)'
(1 3)
```

## Test

Test on the JVM:

    script/test

Although this tool doesn't offer any benefit when running on the JVM, it is
convenient for development.

Test the native version:

    BABASHKA_TEST_ENV=native script/test

## Build

You will need leiningen and GraalVM.

    script/compile

## License

Copyright © 2019 Michiel Borkent

Distributed under the EPL License, same as Clojure. See LICENSE.