Using Tcl_Obj

#include <tcl.h>
  
 typedef struct ShapeFile {
 Tcl_Obj * filename; /* the name of the shape filem */
 Tcl_Channel chan; /* the channel to the openend shape file */
 } ShapeFile;


 static int ShpObjCmd(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj * CONST objv[])
{
 ShapeFile *shp = (ShapeFile*)clientData;
 Tcl_SetObjResult(interp, shp->filename);
 return TCL_OK;
 }
 static int ShpShpCmd ( ClientData cdata, Tcl_Interp *interp, int objc, Tcl_Obj *CONST objv[])
 {
 char *cmdName;
 ShapeFile *shp;
 shp = (ShapeFile*)Tcl_Alloc(sizeof(*shp));
 shp->chan = NULL;
 shp->filename = NULL;
 cmdName = Tcl_GetStringFromObj(objv[1], 0);
 shp->filename = Tcl_DuplicateObj(objv[2]);
 Tcl_CreateObjCommand(interp, cmdName, ShpObjCmd, shp, NULL);
 return TCL_OK;
 }
  
  
 __declspec(dllexport)  int Hello_Init(Tcl_Interp *interp)
 {
 /* we want to use stubs */
 if (Tcl_InitStubs(interp, TCL_VERSION, 0) == NULL) {
 return TCL_ERROR;
 }
 Tcl_CreateObjCommand(interp, "shp", ShpShpCmd, NULL, NULL);
 Tcl_PkgProvide(interp, "Hello", "1.0");
 return TCL_OK;
 }