diff --git a/exemple.sh b/exemple.sh
index 3f6d81d..8a9f738 100755
--- a/exemple.sh
+++ b/exemple.sh
@@ -2,13 +2,20 @@
 
 DATAFILE=/tmp/fake-datafile
 
+#-----  collect the datas
 > ${DATAFILE}
 for s in $(seq 1 20)
 do
-
     v=$(./fake-values 2> /dev/null)
-    echo $s $v | tee -a ${DATAFILE}
+    echo $s $v >> ${DATAFILE}
 done
 
-awk '{print NR " " $2}' < ${DATAFILE}
+#-----  do dome useless computations
+awk	'
+	NR==1	{ debut = $2 }
+		{ print $2-debut, $3 }
+	'                                   \
+< ${DATAFILE}
+
+
 
diff --git a/fake-values.c b/fake-values.c
index 6b412ac..09f95bf 100644
--- a/fake-values.c
+++ b/fake-values.c
@@ -12,7 +12,7 @@ int main(int argc, char *argv[])
 fprintf(stderr, "fake values - %s %s\n", __DATE__, __TIME__);
 
 verbosity = 1;
-printf("%d\n", random1000(0));
+printf("%f %d\n", dtime(), random1000(0));
 
 return 0;
 }
diff --git a/funcs.c b/funcs.c
index 15cba7a..b099c2a 100644
--- a/funcs.c
+++ b/funcs.c
@@ -4,16 +4,35 @@
 
 #include  <stdio.h>
 #include  <stdlib.h>
+#include  <sys/time.h>
 
 #include  "funcs.h"
 
 extern int verbosity;
 
+/* --------------------------------------------------------------- */
+
 int random1000(int foo)
 {
-int     value;
+int         value;
 if (verbosity)
     fprintf(stderr, "%s(%d)\n", __func__, foo);
 value = rand() % 1000;
 return value;
 }
+
+/* --------------------------------------------------------------- */
+
+double dtime(void)
+{
+struct timeval tv;
+int         foo;
+
+foo = gettimeofday(&tv, NULL);
+if (foo) fprintf(stderr, "got %d in %s\n", foo, __func__);
+
+return (double)tv.tv_sec + (double)tv.tv_usec / 1e6;
+}
+
+/* --------------------------------------------------------------- */
+
diff --git a/funcs.h b/funcs.h
index 2319ac4..e142ca8 100644
--- a/funcs.h
+++ b/funcs.h
@@ -3,4 +3,5 @@
  */
 
 int random1000(int mode);
+double dtime(void);