Why won't MATLAB let me open any files, scripts, or anything at all?

If I try opening a file or script by clicking on it from the command window, I get the following error:

Error using fullfile (line 51)
String input not supported.

Error in toolboxdir (line 22)
    s=fullfile(matlabroot,'toolbox', tbxdirname);

Error in matlab.ui.internal.dialog.DialogUtils.imreadDefaultIcon (line 38)
            iconFileName = fullfile(toolboxdir('matlab'), 'uitools', 'private', ['icon_' iconName '_32.png']);

Error in msgbox>setupStandardIcon (line 438)
[iconData, alphaData] = matlab.ui.internal.dialog.DialogUtils.imreadDefaultIcon(iconName);

Error in msgbox (line 353)
        Img = setupStandardIcon(IconAxes, IconString);

Error in errordlg (line 47)
handle = msgbox(ErrorStringCell,DlgName,'error',Replace);

Error in uiopen (line 194)
    errordlg(err);

If I try opening a file by using the open command, I get a different error (see below). Either way, I can't open any scripts at all!

Error using which
Arguments must contain a character vector.

Error in finfo (line 60)
    openAction = which(['open' ext '(''char'')']);

Error in open (line 114)
    [~, openAction] = finfo(fullpath);

Any suggestions? I've been a MATLAB user for 3 years and this has never happened before.

[Walter Roberson]

Could you show us exactly how you are trying to do the open ?

Is it possible that you are getting the file name to open by using uiimport() of a text item?

[Noam Nitzan]

I'm having exactly the same problem but only occasionally, then I have to restart Matlab. Would also like to know how to fix it though, it's pretty annoying. Could it be related to upgrading Matlab? I was using 2012 so far and just upgraded to 2017.

[Steven Lord]

Most of the time when I've seen reports of this type of problem, it occurred because the user created a function with the same name as a MathWorks function but different behavior. If you're only seeing this problem sporadically, it's possible that function is in a directory that is only occasionally on the MATLAB path or is only occasionally your current directory.

The next time you encounter this problem I recommend looking at what's in the current directory and checking (using which) if the function called out in the error message is both a file in that directory and a function included in MATLAB or another MathWorks product.

[Walter Roberson]

You can get those kinds of errors about which and open if you attempt to which() or open() using one of the new string objects instead of a character vector. For example

>> which("polyfit")
Error using which
Arguments must contain a character vector.

One of the ways that you can end up with a string instead of a character vector is if you used uiimport, which in the last couple of releases has defaulted to importing text as string instead of as character vector.

[Walter Roberson]

(R2018a can handle string objects for which())

Answer 1

[Blake Porter]

Opening matlab as administrator fixes this for me. Matlab R2017a

Answer 2

[Walter]

The same problem here. I am confident the code is fine because it runs using 2016a but once upgraded to 2017b nothing works.

[Walter Roberson]

As I posted above,

"One of the ways that you can end up with a string instead of a character vector is if you used uiimport, which in the last couple of releases has defaulted to importing text as string instead of as character vector."