1 files changed, 5 insertions, 0 deletions

diff --git a/tools/markdown/reveal b/tools/markdown/reveal
index f0d374b..4873517 100755
--- a/tools/markdown/reveal
+++ b/tools/markdown/reveal
@@ -1,5 +1,10 @@
 #! /bin/bash
 
+if [[ ! $1 =~ '.md' ]]; then
+  echo markdown file is not given >&2
+  exit 1
+fi
+
 # Available themes:
 # beige black blood league moon night serif simple sky solarized white
 THEME=${THEME:-serif}