m4

Work in progress!

m4 is a pure Javascript implementation of an
m4 macro language processor. You can use it
with Node.js or in the browser, via browserify. It is exposed as a
transformation Stream. As such, you can
easily pipe from any input and to any output.

A command-line version is also provided, usable as a drop-in replacement for a
native version (such as GNU M4).

Installation

npm install m4

If installed locally, the binary is available as node_module/.bin/m4. You
can directly refer to m4 in
npm-scripts.

Example usage

$3

``bash
echo "define(\beep', \boop')dnl\nbeep\n" | m4
#=> boop
`

$3

`js
// example.js
'use strict';

var M4 = require('m4');

var input = new M4();
input.pipe(M4()).pipe(process.stdout);

input.write("define(beep', boop')dnl\nbeep\n");
input.end();
`

Then, in a shell:

`bash
node example.js
#=> boop
`

API

$3

Inherit stream.Transform.
As such this is a duplex stream you can pipe, write and read.

#### new M4(opts)

opts Object* Options:
nestingLimit Number* Maximum nested macro calls. Beware, this
does not prevent endless rescanning loops.

#### Event: 'error'

Signal a non-recuperable error. The stream will not produce further output in
the case of an error.

#### Event: 'warning'

Signal a warning. The steam continues to produce output normally, but there
may be some unwanted behavior.

#### m4.define(name, {fn|str})

name String* Identifier.
fn Fonction* Called with (name, [arg1, arg2 ... ]), must return the
macro expansion result as a string. name is the macro defined name itself.
str String* Macro content, just like you were defining the macro in M4.

Define a M4 macro as a Javascript function.

#### m4.divert([index=0])

index Number* Diversion index.

Change how the output is processed. If the index is zero, output is directly
emitted by the stream. If the index is a positive integer, the output is
stored in an internal buffer — a "diversion" — instead.

#### m4.undivert([diversions...])

diversions Number* Diversion indices.

Output the content of the specified diversions. They are emptied. If no
diversion is specified, all of them are undiverted, in numerical order.

#### m4.dnl()

Put the stream into a special mode where all the tokens are ignored until the
next newline.

#### m4.changeQuote([left], [right])

left String* Characters delimiting the beginning of a string.
right` String* Characters delimiting the end of a string.

Delimiters can be of any length.