Index: /trunk/Ohana/src/opihi/cmd.data/write_vectors.c
===================================================================
--- /trunk/Ohana/src/opihi/cmd.data/write_vectors.c	(revision 10507)
+++ /trunk/Ohana/src/opihi/cmd.data/write_vectors.c	(revision 10508)
@@ -3,4 +3,5 @@
 int write_vectors (int argc, char **argv) {
   
+  int append;
   int i, j, Nvec, Ne, N;
   FILE *f;
@@ -17,11 +18,21 @@
   }
 
+  append = FALSE;
+  if ((N = get_argument (argc, argv, "-append"))) {
+    remove_argument (N, &argc, argv);
+    append = TRUE;
+  }
+
   if (argc < 3) {
-    gprint (GP_ERR, "USAGE: write [-f \"format\"] file vector vector ...\n");
+    gprint (GP_ERR, "USAGE: write [-append] [-f \"format\"] file vector vector ...\n");
     return (FALSE);
   }
 
   /* open file for outuput */
-  f = fopen (argv[1], "w");
+  if (append) {
+      f = fopen (argv[1], "a");
+  } else {
+      f = fopen (argv[1], "w");
+  }
   if (f == (FILE *) NULL) {
     gprint (GP_ERR, "can't open file for write\n");