Index: trunk/Ohana/src/opihi/cmd.data/interpolate.c
===================================================================
--- trunk/Ohana/src/opihi/cmd.data/interpolate.c	(revision 5850)
+++ trunk/Ohana/src/opihi/cmd.data/interpolate.c	(revision 7917)
@@ -9,8 +9,8 @@
   /** check basic syntax **/
   if (argc != 5) {
-    fprintf (stderr, "USAGE: interpolate Xi Yi Xo Yo\n");
-    fprintf (stderr, "  Xi Yi - sorted reference vectors\n");
-    fprintf (stderr, "  Xo    - output positions\n");
-    fprintf (stderr, "  Yo    - output values\n");
+    gprint (GP_ERR, "USAGE: interpolate Xi Yi Xo Yo\n");
+    gprint (GP_ERR, "  Xi Yi - sorted reference vectors\n");
+    gprint (GP_ERR, "  Xo    - output positions\n");
+    gprint (GP_ERR, "  Yo    - output values\n");
     return (FALSE);
   }