CID:1216560 Unchecked return value from ioctl

libs/esl/fs_cli.c

@@ -139,10 +139,10 @@ static void screen_size(int *x, int *y)
 
 #elif defined(TIOCGWINSZ)
 	struct winsize w;
-	ioctl(0, TIOCGWINSZ, &w);
-
-	if (x) *x = w.ws_col;
-	if (y) *y = w.ws_row;
+	if ( (ioctl(0, TIOCGWINSZ, &w)) >= 0 ) {
+		if (x) *x = w.ws_col;
+		if (y) *y = w.ws_row;
+	}
 #else
 	if (x) *x = 80;
 	if (y) *y = 24;