comandante/index.js

spawn() that returns a duplex stream and emits errors with stderr data on non-zero exit codes

var spawn = require('child_process').spawn;
var duplexer = require('duplexer');

module.exports = function (cmd, args, opts) {
    if (Array.isArray(cmd)) {
        opts = args;
        args = cmd.slice(1);
        cmd = cmd[0];
    }
    
    var ps = spawn(cmd, args, opts);
    var err = '';
    if (ps.stderr) {
        ps.stderr.on('data', function (buf) { err += buf });
    }
    
    ps.on('close', function (code) {
        if (code === 0) return;
        dup.emit('error', new Error(
            'non-zero exit code ' + code
            + (!opts || opts.showCommand !== false
                ? '\n  while running: ' + cmd + ' ' + args.join(' ')
                : ''
            )
            + '\n\n  ' + err));
    });
    
    var dup = duplexer(ps.stdin, ps.stdout);
    
    dup.stdin = ps.stdin;
    dup.stderr = ps.stderr;
    dup.stdout = ps.stdout;
    dup.pid = ps.pid;
    dup.kill = ps.kill.bind(ps);
    
    [ 'exit', 'close' ].forEach(function (name) {
        ps.on(name, dup.emit.bind(dup, name));
    });
    
    return dup;
};