Helper module for managing spawned system processes
easy-pipe is a helper wrapper for handling multiple spawn processes.
Easy-pipe is a module designed for easyly spawning child_processes and creating pipelines by piping form one to the other. It also supports streams, so they can be used intermittently.
easy-pipe module exports a function, which can be used to create a PipeStream object.
PipeStream object is the wrapper around Stream and Spawn objects to allow easy connection and handling.
PipeStream object can be created using the easy-pipe function.
The function supports the following input types:
- (EventEmitter) -> the first argument is an EventEmitter object either a Stream or a ChildProcess
- (String, [Array], [Object]) -> the same input as for child_process.spawn, the String however unlike the original spawn command will be split on spaces and all but the first element will be prepended to the Array portion, which will allow simple string spawn commands as seen in previous example
- (Array) -> an array of the previous input types. Every element of the array will be passed through this function again, and the output will be piped along the created PipeStream objects. The last object will be returned.
var $p = require('easy-pipe'); // Using single string input var pipe = $p('tail -f /var/log.txt'); // Using a Stream object var pipe2 = $p(require('fs').createReadStream('/var/log.txt')); // Using a Spawned object var spawn = require('child_process').spawn; var gzip = spawn('gzip', ['/var/log.txt']); var pipe3 = $p(gzip); // Using an array var pipe4 = $p([['tail',['-f','/var/log.txt']],'gzip',require('fs').createWriteStream('/var/log.gz'));
The .pipe method allows to extend the pipeline by one more PipeStream object. A new PipeStream object will be created based on input (view Creating) and the output of current PipeStream object will be Piped to the new. The new PipeStream will be returned, making the process chainable.
var fs = require('fs'); var pipeLine = $p(fs.createReadStream('/var/log.txt')) .pipe('gzip') .pipe(fs.createWriteStream('/var/log.gz'));
All the PipeStream objects will be appended to the internal _pipeline array, and are accessible from all parts of the pipe using the following commands
.get command lets you get the n-th element in the pipeline. Will return PipeStream or false. .last is a convenience function returning the last element in _pipeline .first is a convenience function returning the first element in _pipeline
The .error method allows to append an error listener for the whole pipeline with one command. The function will be called no matter which element in the pipeline broke.
PipeStream object also merges some events under one name.
The stdout['data'] and 'data' data events are merged.
The 'error' and stderr['data'] events are merged
The event handler binding function .on() will return the object so it is chainable.
The MIT License (MIT) Copyright (c) 2012 Karl Düüna
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