Running external commands without going through a shell?

The Matlab system() command allows the user to run external commands. To do this, it spawns a shell, and uses it to run the provided command. (see https://fr.mathworks.com/help/matlab/ref/system.html)

This behavior is great for interactive use. However, for production code, it can cause issues with special characters as the shell will have a tendancy to over-interpret the given commands. So, for example, a directory with parenthesis in its name can cause shell errors and prevent the command from executing properly.

In the Python world, the subprocess module has a way to run commands directly, without spawning a shell (the "shell" argument):

https://docs.python.org/3.9/library/subprocess.html#frequently-used-arguments

Does Matlab have an equivalent? I know people have proposed various regular expressions to escape strings, but that is just not robust enough.

Answer 1

[Jan]

You can try a mex routine: https://www.mathworks.com/matlabcentral/fileexchange/341-spawn

Maybe this works for you:

runtime = java.lang.Runtime.getRuntime();
process = runtime.exec('program arg1 arg2');  % non-blocking
% Continue Matlab processing in parallel to spawned process ...
% ...or:
rc = process.waitFor();    % block Matlab until external program ends
rc = process.exitValue();  % fetch an ended process' return code

[Joël Schaerer]

Thanks! I didn't get a chance to try it yet, but will try to report back when I do.

Answer 2

[Nitin Kapgate]

You can execute operating system commands from the MATLAB command line using the ! operator as an alternative to the system function. The exclamation point character (!), sometimes called bang, is a shell escape. The ! character indicates that the rest of the input line is a command to the operating system.

Use ! to call utilities or other executable programs without quitting MATLAB.

For example, the following code opens the Microsoft Excel on a WINDOWS platform:

!excel.exe

After the external program completes or you quit the program, the operating system returns control to MATLAB.

To run the application in background mode or display the output in a separate window, add & to the end of the line.

For example, the following statement opens the Microsoft Excel program and returns control to the command prompt so that you can continue running MATLAB commands:

!excel.exe &

[Joël Schaerer]

Hi, I don't think the bang operator changes anything regarding my problem.