j7

Filter stdin to stdout with JavaScript

Usage

$ echo '[1,2,3]' | j7 'function main(input) {return JSON.parse(input).join("\n")}'
1
2
3

Command line options

  -j  JSON mode (input is JSON.pars-ed and output is JSON.stringify-ed)
  -l  line-by-line mode (input is filtered line by line)
  -m string
      JS entry point function (default "main")
  -n int
      output size in number of bytes, only effective in conjugation with -j

You can have multiple JS expressions and files to be evaluated. An argument starting with @ is treated as a file path.

j7 'window={}' @/some/library.js 'function main(){return window.foo}'

Examples

$ echo '[1,2,3]' | j7 -j 'function main(input) {return input.filter(function(a) {return a%2===1})}'
[1,3]

$ echo "[1,2,3]\n[4,5,6]" | j7 -l -j 'function main(input){return input[0]}'
1
4

About V7

j7 makes use of the V7 JavaScript engine, a very small JavaScript engine for embedded devices, and it's go binding gov7.

The JavaScript may therefore behave differently from what runs in web browsers. For example, to my knowledge, JSON.stringify only outputs the first 100 bytes. The -j option increases the limit heuristically, but you may sometimes want to specify it with the -n option by yourself.

LICENSE

Because V7 is distributed under the GPLv2, j7 has also adopted GPLv2.