Q:

C++ - Use ofstream to create file in a different directory?

Let's say I want to create a file and my project folder is located inside a folder on my Desktop.  How would I create a file using ofstream onto my desktop?

A:

It seems your question could be reformulated as "How do I get the Desktop Path in a operating system?".
Once you have it, just join it with your filename and then use ofstream. No secrets!
ofstream file;
file.open( YOUR_FULL_PATH_HERE, ios::binary ); // suppose here you want binary!
// write your stuff here...
file.close();

The way you obtain the Desktop path depends on the operating system. In Windows, for example, you can use SHGetSpecialFolderPath( CSIDL_DESKTOP ), but in a Linux or Mac OS X, you gotta check how it's done (probably getenv( "HOME" ) will be enough for you to get the Desktop from the home directory for these "UNIX-based" cases).

