How do I print to stderr?

I'd like to print to standard error. I'm sure there is a simple solution, but the "display" documentation didn't specify, and I didn't find a clear answer when searching this forum. How do you do it in Matlab?

Answer 1

[Michael]

Sorry, the answer is to use fprintf(2,"stuff"). I can't tell if there is a way to get display to print to stdout

Answer 2

[Walter Roberson]

Unfortunately MATLAB does not support stdout or stderr. The closest it has is writing to file 1 (sort of like stdout) or file 2 (sort of like stderr). Both file 1 and file 2 will go to wherever the command output is going, such as the command window. Neither of them are connected to the Unix stderr stream. If the session was started with -nodisplay (or equivalent) so that there is no command window, then both of them are connected to stdout -- but if the command window is active, then neither of them are connected to stdout.

The only difference I have been able to infer in MATLAB between writing to file 1 and file 2, is that it appears from one of the documentation examples (somewhere) that file 2 might not be buffered, that output to it might potentially get mixed in with output that is already in progress.

[Michael]

Thank you. I will add this to the list of reasons to use Pylab ( <a href="http://www.scipy.org/PyLab">link</a> ). This makes monitoring of remote Matlab jobs difficult, if errors cannot be separated from valid output.

[Gabriele Bellomia]

Just to clarify for the 2022 reader: I don't know if the behavior has changed and when this would have happened but I can confirm that with MATLAB > R2020b 'fprinting' to '2' totally works for remote hpc workflows. In particular I succesfully tested the behavior on a SLURM-managed CentOS machine, and I consistently find all the fprintf(2,...) outputs in the stderr logs built by SLURM. :)