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The best compromise I can think of would be to prepend the line source to the combined output, so lines in the combined output can be distinguished. But depending on how you do that, you might have timing issues. In fact, any form of interleaving the outputs of stderr and stdout are technically subject to timing issues because even the source application can’t specify that bytes in one stream should follow bytes in another stream. https://stackoverflow.com/questions/12517519/how-to-redirect... talks a bit about the problem, and I’m sure someone somewhere has written a general-purpose tool, but there are timing edge cases here and often the solution is seen as keeping errors messages exclusively in stdout (or logs) or more practically, not worrying about preserving order and writing errors exclusively to stderr without worrying as much about strictly when errors interleave. If you add timestamps to your line outputs, or add some form of line numbers to the output, you can restore order after logging but it would be application-specific to do so. From a practical perspective, listening to both streams and quickly appending to a list with a data structure containing the source and message text is probably your closest approximation if writing code to handle output streams and you want an combined output that can still source which stream came from which source. (Again subject to timing errors)