fix the command and add an app check

ximpershot

@@ -117,7 +117,7 @@ process_screenshot() {
     case "$app" in
         "")
             if [ "$output_file" = "-" ]; then
-                grim -g "${geometry}" --stdout
+                grim -g "${geometry}" -
             elif [ -n "$output_file" ]; then
                 grim -g "${geometry}" "$output_file"
             fi
@@ -148,7 +148,7 @@ save_geometry() {
 	fi
 	
 	if [ "$COMMAND" ]; then
-		wayshot -s "${geometry}" --stdout | $COMMAND
+		grim -g "${geometry}" - | $COMMAND
 		return
 	fi
 	    
@@ -231,8 +231,13 @@ while true; do
        	*)
        		print_error "Неверная опция: $1"
        		;;
-       	
     esac
 done
 
+if [ -n "$OUTPUT_APP" ]; then
+    if ! command -v "$OUTPUT_APP" > /dev/null 2>&1; then
+        print_error "Программа $OUTPUT_APP не установлена."
+    fi
+fi
+
 begin_grab $MODE