C++ Visual Studio 2010 how to use a char type variable in different functions

Question

I'm having a problem regarding a char type variable in my program. I don't post the code because it is too long but this is roughly what I want to do:

#include ...

char path[100];

int main()
{
    char path[100] = "C:/......";

    [...]

    out = function();
}

int function()
{
    [...]
    imwrite(path,image);
    [...]

} 

The problem is that my path variable seems to be lost somehow because if I try cout < < path before imwrite in function it doesen't print anything as if path was empty.

What should I do forbeing able to access my path variable in function?

Answer 1

You are defining the path variable within the scope of your main function, as well as in the global scope.

In main() you have a new declaration of path :

char path[100] = "...";

This effectively gives you two variables with the same name, but in different scopes. If you access path from within the main method, it will access the locally-scoped variable.

If you wish to keep it this way, and remove the globally-scoped path variable, you could redeclare your function to:

int function(char* p_path)
{
    imwrite(p_path, image);
}

and pass the value as a parameter from main:

char path[100] = "...";
...
function(path);

As an aside, you could force access of the globally-scoped variable from within the main method by referencing ::path , which specifies the global namespace. But that's another story.

Answer 2

You're defining a global variable path (in global scope) and a local variable path in main() . This means that inside main() , path refers to the local one, while in function() , it refers to the global one.

If the path is hardcoded (as in the example you gave), you can do this:

#include ...

char path[100] = "C:/......";

int main()
{
    [...]

    out = function();
}

If the path needs to be computed, do this instead:

#include ...

char path[100];

int main()
{
    [...]
    std::copy(computedPathValue, computedPathValue + computedPathLength + 1, path);

    out = function();
}

Of course, the best would be to have std::string path instead of a char[100] .