expand file names that have environment variables in their path

user_180635 0
Viewed 26627

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.

wxwidgets boost-filesystem c++
8 Answers
user_337320

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.

user_5606350
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