There was a mistake in GetOptions : something like

if(degree != 1 || degree != 2) which was always true,
giving an error when doing the command line gmsh -degree 2

Common/DefaultOptions.h

@@ -217,7 +217,7 @@ StringXNumber MeshOptions_Number[] = {
 StringXNumber PostProcessingOptions_Number[] = {
   { F|O, "Scales" , opt_post_scales , 1. }, 
   { F|O, "Link" , opt_post_link , 0. }, 
-  { F|O, "Smoothing" , opt_post_smooth , 0. }, 
+  { F|O, "Smoothing" , opt_post_smooth , 1. }, 
   { F|O, "AnimationDelay" , opt_post_anim_delay , 0.25 }, 
   { F, "NbViews" , opt_post_nb_views , 0. }, 
   { 0, NULL , NULL , 0. }

Common/GetOptions.cpp

-// $Id: GetOptions.cpp,v 1.13 2001-02-22 08:16:30 geuzaine Exp $
+// $Id: GetOptions.cpp,v 1.14 2001-02-22 14:43:39 remacle Exp $
 
 #include "Gmsh.h"
 #include "GmshUI.h"
@@ -188,7 +188,7 @@ void Get_Options (int argc, char *argv[], int *nbfiles) {
         i++;
         if(argv[i]!=NULL){
           CTX.mesh.degree = atoi(argv[i++]);
-          if(CTX.mesh.degree != 1 || CTX.mesh.degree != 2){
+          if(CTX.mesh.degree != 1 && CTX.mesh.degree != 2){
             fprintf(stderr, ERROR_STR "Wrong Degree\n");
             exit(1);
           }