diff --git a/sys/subst.sh b/sys/subst.sh
new file mode 100755
index 0000000000..5f66a01460
--- /dev/null
+++ b/sys/subst.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+a="$1"
+b="$2"
+if [ -z "$a" ]; then
+	echo "Usage: sys/subst.sh [old] [new]"
+	exit 1
+fi
+#[ -z "$a" ] && a="r_str_chop "
+#[ -z "$b" ] && b="r_str_trim "
+git grep "$a" libr binr | less -R
+if [ -n "$b" ]; then
+	FILES=`git grep "$a" libr binr | cut -d : -f 1 | uniq `
+	for f in $FILES ; do
+		echo "Sedded $a"
+		sed -e "s/$a/$b/g" < $f > $f.sub
+		mv $f.sub $f
+	done
+else
+	echo "Oops"
+fi