Fix crash bug, update docHEADmaster

2 files changed, 39 insertions, 6 deletions

diff --git a/README.md b/README.md
index 0a02297..a28345f 100644
--- a/README.md
+++ b/README.md
@@ -2,3 +2,37 @@
 The X11 bouncing DVD logo. A little gimmick for a new video.
 
 ![Screen capture of xbouncing in action](doc/animated.webp)
+
+## Cloud Demo
+If you're running Linux, you can simply use SSH X11 forwarding to try it out
+without installing anything at all. However, due to network delay, it won't be
+as smooth as running it on your machine locally.
+
+```
+ssh -X dvd@sshs.snart.me
+```
+
+If you're running Mac or Windows, you may use **XQuartz** or **Xming**.
+
+## INSTALL
+To build it from source and run it on your machine yourself,
+
+```sh
+sudo dnf install git cmake gcc libX11-devel libXrandr-devel
+
+git clone https://github.com/dxdxdt/xbouncing
+cd xbouncing
+
+cmake -B build
+cd build
+
+make
+sudo make install
+```
+
+## Usage
+```sh
+xbouncing
+```
+
+Interrupt(`Ctrl` + `C`) or terminate.
diff --git a/src/xbouncing.c b/src/xbouncing.c
index d1f83b4..2f15ef0 100644
--- a/src/xbouncing.c
+++ b/src/xbouncing.c
@@ -127,13 +127,12 @@ static void update_screen_info (void) {
 
 static void print_l18n_xopen_err (void) {
 	const char *LANG = getenv("LANG");
-	const char *msg;
+	const char *msg = "Could not open X display.";
 
-	if (strncmp(LANG, "ko", 2) == 0) {
-		msg = "X 서버 연결 실패.";
-	}
-	else {
-		msg = "Could not open X display.";
+	if (LANG != NULL) {
+		if (strncmp(LANG, "ko", 2) == 0) {
+			msg = "X 서버 연결 실패.";
+		}
 	}
 
 	fprintf(stderr, "%s\n", msg);