How to save all global variables?

The save command only saves those Matlab variables which are visible in a workspace. It does not, however, cover the global variables which are reported by who('global') but have not been declared as globals in this workspace. Is there a way to save all global variables in a given Matlab session, even if their names are not known a priori?

[Stephen23]

Read these:

https://www.mathworks.com/matlabcentral/answers/281678-automatically-define-global-variables

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Answer 1

[Jan]

While I recommend not to use global variables, because they impede the debugging dramatically, there should be a solution to your problem.

When you want to save the variables, which are found by who('global'), it would be a simple idea to use globalVars = who('global') to get a list of these variables at first. Then the values might not be known inside a function. So, sigh, I have to suggest to one and only case, which I cannot solve without eval.

globalVars = who('global');
for iVar = 1:numel(globalVars)
  eval(sprintf('global %s', globalVars{iVar}));  % [EDITED]
end

This can overwrite local variables by accident, e.g. if "globalVars" is a global variable itself, this approach is buggy. Therefore I strongly recommend to choose a different strategy. The complexity caused by the automatic access of global variables cannot be managed reliably. And when there is the decision between a complicated and inherently buggy method and a clean and clear one, <not every sentence has to be finished>

[Guido]

Thanks a lot. That helped quite a bit. There is just a small typo in the answer. The sigh line should read

    eval(sprintf('global %s', globalVars{iVar}));

[Jan]

Typo is fixed. But I have a bad conscience that I suggest a method containing the two evil commands EVAL and GLOBAL simultaneously. Hopefully nobody has seen this and reminds me, when I claim vainly, that there are always better ways then EVAL.

[Sean Herbert]

another way, without a for loop:

    globalVars = who('global')'; %notice the '
    glob_str = sprintf('global %s',strjoin(globalVars));

    %create them
    eval(glob_str)

[Stephen23]

These "solutions" should all be given the caveat "Only for entertainment purposes, NEVER use in serious code!"

Answer 2

[Tarun Luthra]

I am trying to do same thing. how do I save something inside a function such as a global variable out to workspace?