apps: Add a little screen utility

It tells you the resolution of your screen :)

apps/Makefile

@@ -1,4 +1,4 @@
-APPS := init sh uname uptime hello ps ls args cat stat su session date mkdir
+APPS := init sh uname uptime hello ps ls args cat stat su session date mkdir screen
 
 APPS_DIR := $(LUNA_ROOT)/apps
 APPS_SRC := $(APPS_DIR)/src

apps/src/screen.c

@@ -0,0 +1,32 @@
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <stdio.h>
+
+int main()
+{
+    int fd = open("/dev/fb0", O_WRONLY | O_CLOEXEC);
+    if(fd < 0)
+    {
+        perror("open");
+        return 1;
+    }
+
+    int fb_width = ioctl(fd, FB_GET_WIDTH);
+    if(fb_width < 0)
+    {
+        perror("ioctl(FB_GET_WIDTH)");
+        return 1;
+    }
+
+    int fb_height = ioctl(fd, FB_GET_HEIGHT);
+    if(fb_height < 0)
+    {
+        perror("ioctl(FB_GET_HEIGHT)");
+        return 1;
+    }
+
+    printf("Your screen is %dx%d\n", fb_width, fb_height);
+
+    close(fd);
+}