Skip saving output to variable when using callback function

[stefandoorn]

My case is currently that I'm streaming use log files using sh::cat() and using a callback closure to pass the data (after a filter) to an PHPExcel object. The log files can easily get over 500MB. Looking through the code it seems that even when using a callback/closure, the output of the cat command still gets saved to a variable, making memory usage go up and up.

I cannot grep on the log files as it's filled with IDs, possible conflicting with other data in the same line.

Is this currently possible in a less memory consuming way? Else I'm also willing to submit a PR with some extra functionality on this. Reasoning could be that when streaming through a closure, no need is left to save things to the self::$output variable.