These procedures may be used to manipulate the current working
directory for the application. They provide C-level access to
the same functionality as the Tcl pwd command.
Tcl_GetCwd returns a pointer to a string specifying the current
directory, or NULL if the current directory could not be determined.
If NULL is returned, an error message is left in the interps result.
Storage for the result string is allocated in bufferPtr; the caller
must call Tcl_DStringFree() when the result is no longer needed.
The format of the path is UTF-8.
Tcl_Chdir changes the applications current working directory to
the value specified in path. The format of the passed in string
must be UTF-8. The function returns -1 on error or 0 on success.