Worksession Variables - MATLAB

Question

I'm writing a series of MATLAB functions which communicate with a server through urlread. Each function in this package that makes this call requires an authentication username and key.

I would rather not require the user to pass in the username and key when calling every function. Instead, I prefer to have a signin(username, key) function that sets/saves these variables in such a way that each function in this package can recall.

My solution right now is for signin.m to save username and key to a temporary file and to modify finish.m to erase this temporary file when MATLAB closes. Each function in the package would load these variables from that temporary file. However, if someone force quits MATLAB, this temporary file will not be erased (right?).

Another solution was to have signin save username and key as global variables. However, if a user calls clear all, these variables will be removed the workspace and the user will need to call signin again (which is a nuisance).

Is there some way to set 'session' variables that are global and are not removed with a clear all command? Any other suggestions?

Pursuit Pursuit · Accepted Answer · 2013-05-30T23:00:30

You're almost there. A few useful features:

persistent

First, you should be using persistent variables rather than global variables. They are like globals, but scoped to a single function. They're just better.

mlock

Run mlock within a function to prevent the clear or clear all command from clearing data associated with that function.

So, for example, you could define a quick function to help a username and key within a Matlab sessionb as follows:

function [name, key] = credentials(varargin)
persistent USERNAME KEY
if nargin==3 && ischar(varargin{1}) && strcmpi(varargin{1},'set')
    USERNAME = varargin{2};
    KEY= varargin{3};
    mlock;
else
    name = USERNAME;
    key = KEY;
end

Then you could use it like this:

%First, set the credentials
credentials set SOMEUSERNAME SOMEKEY

% ....  do some work ....

clear   %As part of your work, clear all variables

% ....  do some more work ....


%Get the credentials later
[name, key] = credentials;

Worksession Variables - MATLAB

3 Answers