Why do I get a permission denied error in regards to classpath.txt or pathdef.m when starting MATLAB?

MATLAB does not start properly or run after being started. The command window displayed this error:

ERROR: C:\Program Files\MATLAB\R2012b\toolbox\local\classpath.txt: Cannot open file: permission denied.

OR

ERROR: C:\Program Files\MATLAB\R2012b\toolbox\local\pathdef.m: Cannot open file: permission denied.

How can I fix this error?

Answer 1

[MathWorks Support Team]

This error indicates that the user account you are executing MATLAB under does not have Read permissions for the classpath.txt or pathdef.m file, which is required to run MATLAB.

To resolve this issue, navigate to the file's location (see path in error message) and add Read permissions for your user. If you are unable to change permissions on your machine, contact your system administrator.

If any files are missing, try a clean re-installation of the software.

[Jan]

A user account without read permissions? Then Matlab should not start at all. Do you mean write permissions?

This is a really bad idea. Under Windows Matlab is installed in the Program Files folder as default. Changing the permissions for the complete installation folder is a severe drawback from the viewpoint of security. Then a virus do not need to elevate its permissions to infect an executable.

In addition users can modify Matlab's toolbox functions by accident afterwards. Concerning problem occurred repeatedly in this forum: a user opens a toolbox file in the editor and hits any key without beeing aware. Then closing the editor asks for saving and "ok" sounds fair.

See my answer for further ideas.

Answer 2

[Jan]

Better change the permissions for the pathdef.m and classpath.txt files only, or at least only <matlabroot>\toolbox\local. This has a drawback on a multi-user machine: Then all users can adjust pathdef.m to you needs and the next user might be confused.

Prefer user-defined pathdef.m files inside a folder belonging to the user path. This is save and allows individual changes.

I'm using a different strategy: I've edited the <matlabroot>\toolbox\local\pathdef.m to add the folder "D:\MFiles\Inits". This fiolder contains user defined functions to add the personal set of folders to the path dynamically. This allows multiple users to work on one machine and different projects or versions also without the danger of interferences.

[yunhui zhou]

On MATLAB R2018b, R2019a and R2019b copying pathdef.m to user specific directory sometimes cause the parallel computing toolbox to stuck in launching the parallel workers. "Start parallel pool" will never end without an error message. This happens only occasionally (10-30% I guess), but is really annoying. I have been dealing it for months without any idea of the cause but one day after I removed the user-specific pathdef.m the problem was gone.

Answer 3

[埃博拉酱]

This is a very ugly design!

All path settings should be user-wide instead of system-wide by default! MATLAB default pathdefs should stay in Installation folder still, but each user should have his own self-added pathdef in the user directory like %APPDATA%\MathWorks\MATLAB\R2021b! Then each user can edit his own pathdef as he like, without any side effect on other users!