docs: function cmdProcess(file, flow, command, startFn, doneFn){
    var packStartTime = new Date;
    var fconsole = flow.console;
    var gcc;
  
    fconsole.log('Init compression for ' + file.relOutputFilename);
    gcc = exec(
      command, {
        maxBuffer: 10 * 1024 * 1024
      }, function(error, stdout, stderr){
        stderr = String(stderr || '').replace(/^The compiler is waiting for input via stdin\.\r?\n/, '');
  
        if (stderr)
        {
          var errorMsg;
  
          if (stderr.match(/^stdin:(\d+):\s+(.+)/))
          {
            var CHARS = 40;
            var lines = stderr.split(/\r\n?|\n\r?/);
            var m = (lines[2] || '').match(/^\s*/);
            var pos = (m ? m[0].length : 0);
            var left = Math.min(pos, CHARS);
  
            errorMsg =
              lines[0] + '\n' +
              (pos > CHARS ? '...' : '') +
              lines[1].substr(pos - left, CHARS) +
              lines[1].substr(pos, CHARS) +
              (pos + CHARS < stderr.length ? '...' : '') + '\n' +
              repeat(' ', left + (pos > CHARS ? 3 : 0)) + '^';
          }
          else
            errorMsg = stderr.length < 256
              ? stderr
              : stderr.substr(0, 128) + '...' + stderr.substr(stderr.length - 128);
  
          flow.warn({
            fatal: true,
            message:
              file.relOutputFilename + ' compression error:\n' +
              errorMsg
          });
  
          return doneFn();
        }
  
        fconsole.log(file.relOutputFilename + ' compressed in ' + ((new Date - packStartTime) / 1000).toFixed(3) + 's');
        if (error !== null)
          fconsole.log('exec error: ' + error);
        else
          file.outputContent = stdout.replace(/;[\r\n\s]*$/, '');
  
        doneFn();
      }
    );
  
    startFn();
    gcc.stdin.on('error', function(error){
      flow.warn({
        fatal: true,
        message:
          'Pack command: `' + command + '`\n' +
          error
      });
    });
    gcc.stdin.write(file.outputContent);
    gcc.stdin.end();
  }