expand file names that have environment variables in their path

Question

What's the best way to expand

${MyPath}/filename.txt to /home/user/filename.txt

or

%MyPath%/filename.txt to c:\Documents and settings\user\filename.txt

with out traversing the path string looking for environement variables directly? I see that wxWidgets has a wxExpandEnvVars function. I can't use wxWidgets in this case, so I was hoping to find a boost::filesystem equivalent or similar. I am only using the home directory as an example, I am looking for general purpose path expansion.

Answer 1

some weird solution until someone will propose a real one: at least on Windows you can execute "echo "+string command and read its output :)

Answer 2

On Windows, you can use ExpandEnvironmentStrings. Not sure about a Unix equivalent yet.

Answer 3

Some platforms and compilers allow a third parameter to the main() function pointing to the environment variables. Search your compiler documentation.

Answer 4

Try getenv. Here is an example taken verbatim from cplusplus.com:

/* getenv example: getting path */
#include <stdio.h>
#include <stdlib.h>

int main ()
{
  char * pPath;
  pPath = getenv ("PATH");
  if (pPath!=NULL)
    printf ("The current path is: %s",pPath);
  return 0;
}