updated code

wallpaperd.c

@@ -11,13 +11,17 @@
 #include <signal.h>
 #include <dirent.h>
 #include <sys/stat.h>
+#include <sys/file.h>
+
+#define LOCK_FILE "/tmp/my_wallpaperd.lock"
+#define SOCKET_FILE "/tmp/my_wallpaper.sock"
 
 
 int initServerSockServer() {
     int server_fd = socket(AF_UNIX, SOCK_STREAM, 0);
     struct sockaddr_un addr = {0};
     addr.sun_family = AF_UNIX;
-    strcpy(addr.sun_path, "/tmp/my_wallpaper.sock");
+    strcpy(addr.sun_path, SOCKET_FILE);
     unlink(addr.sun_path);
     if (server_fd < 0) perror("socket");
     if (bind(server_fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) perror("bind");
@@ -168,9 +172,26 @@ void handleCommand(char *buff, int n, char** images, size_t image_count){
     }
 }
 
+
+
 int main(int argc, char** argv) {
+
+    int fd = open(LOCK_FILE, O_CREAT | O_RDWR, 0666);
     printf("INFO: daemon started\n");
     
+    if (fd == -1) {
+        perror("ERROR: Failed to open lock file");
+        return 1;
+    }
+
+    if (flock(fd, LOCK_EX | LOCK_NB) == -1) {
+        fprintf(stderr, "INFO: Another instance is already running.\n");
+        fprintf(stderr, "INFO: exiting\n");
+        close(fd);
+        return 1;
+    }
+
+
     char** images = NULL;
     size_t image_count = 0;
 
@@ -182,21 +203,22 @@ int main(int argc, char** argv) {
     struct stat stat_buffer;
 
     if(stat(argv[1], &stat_buffer) != 0){
-        printf("dirpath is invalid\n");
+        printf("ERROR: dirpath is invalid\n");
         return 1;
     }
     
     if(stat(argv[2], &stat_buffer) != 0){
-        printf("filepath is invalid\n");
+        printf("ERROR: filepath is invalid\n");
         return 1;
     }
+    
     static_wallpaper_path = argv[2];
     collectImages(argv[1], &images, &image_count);
-    printf("collected %ld suitable images\n", image_count);
+    printf("INFO: collected %ld suitable images\n", image_count);
     shuffleImages(images, image_count);
-    printf("images shuffled\n");
+    printf("INFO: images shuffled\n");
     
-    printf("starting server\n");
+    printf("INFO: starting server\n");
     int server_fd = initServerSockServer();
 
     setBackgroundImage(images[0]);
@@ -212,7 +234,7 @@ int main(int argc, char** argv) {
         int ret = select(server_fd + 1, &fds, NULL, NULL, &tv);
 
         if (ret < 0) {
-            perror("select\n");
+            perror("ERROR: select\n");
             break;
         }