How to read from stdin in Matlab

Question

I have a long-running Matlab script for data processing. I want to send it a flag over stdin to tell it I have new data to process. I also want to read a flag from stdout when it is done processing.

In other words, I have a Process A that sends a flag about once a minute to Matlab. I want Matlab to wait until it receives this flag.

Writing to stdout in a matlab process is as easy as calling fprintf. But how can I read from stdin? Documentation on fopen doesn't mention an input pipe, and neither does fread. How can get a Matlab script to read from stdin?

Answer 1

It actually turns out that the solution is as simple as input. Write the following into myscript.m:

str = input('', 's'); 
fprintf(str); 
exit;

Then, run the following in a shell:

echo Hello world | matlab -nosplash -nodisplay -nodesktop -r "myscript"

Indeed, we see that "Hello world" is printed to the console, along with Matlab's startup text.

So, in summary, input reads from stdin, and fprintf writes to stdout.