Implement -U for Linux

doc/man.md.j2

@@ -160,6 +160,11 @@ file.
 
 :   Update interval.
 
+**-U \| \--unique**
+
+:   Conky won't start if another Conky process is already running. Implemented
+    only for Linux.
+
 **-v \| -V \| \--version** 
 
 :   Prints version, build information and general info. Exits after

src/conky.cc

@@ -2107,6 +2107,9 @@ void set_current_config() {
 /* : means that character before that takes an argument */
 const char *getopt_string =
     "vVqdDSs:t:u:i:hc:p:"
+#if defined(__linux__)
+    "U"
+#endif
 #ifdef BUILD_X11
     "x:y:w:a:X:m:f:"
 #ifdef OWN_WINDOW
@@ -2136,7 +2139,12 @@ const struct option longopts[] = {
     {"double-buffer", 0, nullptr, 'b'}, {"window-id", 1, nullptr, 'w'},
 #endif /* BUILD_X11 */
     {"text", 1, nullptr, 't'},          {"interval", 1, nullptr, 'u'},
-    {"pause", 1, nullptr, 'p'},         {nullptr, 0, nullptr, 0}};
+    {"pause", 1, nullptr, 'p'},
+#if defined(__linux__)
+    {"unique", 0, nullptr, 'U'},
+#endif /* Linux */
+    {nullptr, 0, nullptr, 0}
+};
 
 void setup_inotify() {
 #ifdef HAVE_SYS_INOTIFY_H

src/linux.cc

@@ -3147,3 +3147,45 @@ void get_top_info(void) {
   calc_io_each(); /* percentage of I/O for each task */
 #endif            /* BUILD_IOSTATS */
 }
+
+/******************************************
+ * Check if more than one conky process   *
+ * is running                             *
+ ******************************************/
+
+bool is_conky_already_running(void) {
+  DIR *dir;
+  struct dirent *ent;
+  char buf[512];
+  int instances = 0;
+
+  if (!(dir = opendir("/proc"))) {
+    NORM_ERR("can't open /proc: %s\n", strerror(errno));
+    return false;
+  }
+
+  while ((ent = readdir(dir)) != NULL) {
+    char *endptr = ent->d_name;
+    long lpid = strtol(ent->d_name, &endptr, 10);
+    if (*endptr != '\0') {
+      continue;
+    }
+
+    snprintf(buf, sizeof(buf), "/proc/%ld/stat", lpid);
+    FILE *fp = fopen(buf, "r");
+    if (!fp) {
+      continue;
+    }
+
+    if (fgets(buf, sizeof(buf), fp) != NULL) {
+      char *conky = strstr(buf, "(conky)");
+      if (conky) {
+        instances++;
+      }
+    }
+    fclose(fp);
+  }
+
+  closedir(dir);
+  return instances > 1;
+}

src/linux.h

@@ -58,6 +58,8 @@ int update_stat(void);
 
 void print_distribution(struct text_object *, char *, unsigned int);
 
+bool is_conky_already_running(void);
+
 extern char e_iface[64];
 extern char interfaces_arr[MAX_NET_INTERFACES][64];
 

src/main.cc

@@ -44,6 +44,10 @@
 #include "ccurl_thread.h"
 #endif /* BUILD_CURL */
 
+#if defined(__linux__)
+#include "linux.h"
+#endif /* Linux */
+
 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
 #include "freebsd.h"
 #endif /* FreeBSD */
@@ -268,8 +272,11 @@ static void print_help(const char *prog_name) {
          "   -i COUNT                  number of times to update " PACKAGE_NAME
          " (and quit)\n"
          "   -p, --pause=SECS          pause for SECS seconds at startup "
-         "before doing anything\n",
-         prog_name);
+         "before doing anything\n"
+#if defined(__linux__)
+         "   -U, --unique              only one conky process can be created\n"
+#endif /* Linux */
+         , prog_name);
 }
 
 inline void reset_optind() {
@@ -293,6 +300,8 @@ int main(int argc, char **argv) {
   g_sighup_pending = 0;
   g_sigusr2_pending = 0;
 
+  bool unique_process = false;
+
 #ifdef BUILD_CURL
   struct curl_global_initializer {
     curl_global_initializer() {
@@ -349,12 +358,23 @@ int main(int argc, char **argv) {
         window.window = strtol(optarg, nullptr, 0);
         break;
 #endif /* BUILD_X11 */
-
+#if defined(__linux__)
+      case 'U':
+        unique_process = true;
+        break;
+#endif /* Linux */
       case '?':
         return EXIT_FAILURE;
     }
   }
 
+#if defined(__linux__)
+  if (unique_process && is_conky_already_running()) {
+    NORM_ERR("already running");
+    return 0;
+  }
+#endif /* Linux */
+
   try {
     set_current_config();