There have been earlier reports about this before (TOOLS-1484). Mongodump writes all kinds of debugging output to stderr, even if the command succeeded. Whilst I agree checking the exit code is the correct way to check for errors this behaviour makes it frustrating to send the actual error to another system as it is thousands of lines long without reason.

The --quiet option is even worse as that hides the error altogether.

Is it possible to write the normal log lines to stdout and just the errors to stderr? If that is not possible (I think not all platforms might support this) is it possible to either improve the --quiet option or add a new option that only suppresses non-error output?