Since ffmpeg likes to spew onto stderr and I didn't want to combine the streams I opted for this approach.

Features:
* Run and stay resident shell process saves on shell proc construct/destruct ops
* Can attach to stderr and/or stdout per line("\r\n","\r","\n") with a callback
* Can background a process easily

-- Potential Improvements --
* some setter/getter for what ENV to pass to shell (instead of being hard coded) 

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-- CODE --
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$bash = new Bash(); 

### Optional callback (stdout)
#$callback = function($line) { printf("callbackLine: %s\r\n", $line); };
#$result = $bash->run("ls -l",false,$callback);

# see $bash->run() code docs for invocation options and expected return types.

$result = $bash->run("ls -l");
var_export($result);