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:\\Document         


        

Answer 1

Within the C/C++ language, here is what I do to resolve environmental variables under Unix. The fs_parm pointer would contain the filespec (or text) of possible environmental variables to be expanded. The space that wrkSpc points to must be MAX_PATH+60 chars long. The double quotes in the echo string are to prevent the wild cards from being processed. Most default shells should be able to handle this.

   FILE *fp1;

   sprintf(wrkSpc, "echo \"%s\" 2>/dev/null", fs_parm);
   if ((fp1 = popen(wrkSpc, "r")) == NULL || /* do echo cmd     */
       fgets(wrkSpc, MAX_NAME, fp1) == NULL)/* Get echo results */
   {                        /* open/get pipe failed             */
     pclose(fp1);           /* close pipe                       */
     return (P_ERROR);      /* pipe function failed             */
   }
   pclose(fp1);             /* close pipe                       */
   wrkSpc[strlen(wrkSpc)-1] = '\0';/* remove newline            */

For MS Windows, use the ExpandEnvironmentStrings() function.