Code changes to support FreeBSD

* Code changes to support FreeBSD

Author: abraunegg

src/main.d

@@ -867,11 +867,9 @@ int main(string[] cliArgs) {
 			performFileSystemMonitoring = true;
 
 			// What are the current values for the platform we are running on
-			// Max number of open files /proc/sys/fs/file-max
-			string maxOpenFiles = strip(readText("/proc/sys/fs/file-max"));
+			string maxOpenFiles = strip(getMaxOpenFiles());
 			// What is the currently configured maximum inotify watches that can be used
-			// /proc/sys/fs/inotify/max_user_watches
-			string maxInotifyWatches = strip(readText("/proc/sys/fs/inotify/max_user_watches"));
+			string maxInotifyWatches = strip(getMaxInotifyWatches());
 
 			// Start the monitor process
 			addLogEntry("OneDrive synchronisation interval (seconds): " ~ to!string(appConfig.getValueLong("monitor_interval")));
@@ -1238,6 +1236,54 @@ int main(string[] cliArgs) {
 	}
 }
 
+// Retrieves the maximum number of open files allowed by the system
+string getMaxOpenFiles() {
+    version (Linux) {
+        try {
+            // Read max open files from procfs on Linux
+            return strip(readText("/proc/sys/fs/file-max"));
+        } catch (Exception e) {
+            return "Unknown (Error reading /proc/sys/fs/file-max)";
+        }
+    } else version (FreeBSD) {
+        try {
+            // Read max open files using sysctl on FreeBSD
+            return strip(executeShell("sysctl -n kern.maxfiles").output);
+        } catch (Exception e) {
+            return "Unknown (sysctl error)";
+        }
+    } else version (OpenBSD) {
+        try {
+            // Read max open files using sysctl on OpenBSD
+            return strip(executeShell("sysctl -n kern.maxfiles").output);
+        } catch (Exception e) {
+            return "Unknown (sysctl error)";
+        }
+    } else {
+        return "Unsupported platform";
+    }
+}
+
+// Retrieves the maximum inotify watches allowed (Linux) or a placeholder for other platforms
+string getMaxInotifyWatches() {
+    version (Linux) {
+        try {
+            // Read max inotify watches from procfs on Linux
+            return strip(readText("/proc/sys/fs/inotify/max_user_watches"));
+        } catch (Exception e) {
+            return "Unknown (Error reading /proc/sys/fs/inotify/max_user_watches)";
+        }
+    } else version (FreeBSD) {
+        // FreeBSD uses kqueue instead of inotify, no direct equivalent
+        return "N/A (uses kqueue)";
+    } else version (OpenBSD) {
+        // OpenBSD uses kqueue instead of inotify, no direct equivalent
+        return "N/A (uses kqueue)";
+    } else {
+        return "Unsupported platform";
+    }
+}
+
 // Print error message when --sync or --monitor has not been used and no valid 'no-sync' operation was requested
 void printMissingOperationalSwitchesError() {
 	// notify the user that --sync or --monitor were missing

src/monitor.d

@@ -57,13 +57,19 @@ class MonitorBackgroundWorker {
 		int wd = inotify_add_watch(fd, toStringz(pathname), mask);
 		if (wd < 0) {
 			if (errno() == ENOSPC) {
-				// Get the current value
-				ulong maxInotifyWatches = to!int(strip(readText("/proc/sys/fs/inotify/max_user_watches")));
-				addLogEntry("The user limit on the total number of inotify watches has been reached.");
-				addLogEntry("Your current limit of inotify watches is: " ~ to!string(maxInotifyWatches));
-				addLogEntry("It is recommended that you change the max number of inotify watches to at least double your existing value.");
-				addLogEntry("To change the current max number of watches to " ~ to!string((maxInotifyWatches * 2)) ~ " run:");
-				addLogEntry("EXAMPLE: sudo sysctl fs.inotify.max_user_watches=" ~ to!string((maxInotifyWatches * 2)));
+				version (Linux) {
+					// Read max inotify watches from procfs on Linux
+					ulong maxInotifyWatches = to!int(strip(readText("/proc/sys/fs/inotify/max_user_watches")));
+					addLogEntry("The user limit on the total number of inotify watches has been reached.");
+					addLogEntry("Your current limit of inotify watches is: " ~ to!string(maxInotifyWatches));
+					addLogEntry("It is recommended that you change the max number of inotify watches to at least double your existing value.");
+					addLogEntry("To change the current max number of watches to " ~ to!string((maxInotifyWatches * 2)) ~ " run:");
+					addLogEntry("EXAMPLE: sudo sysctl fs.inotify.max_user_watches=" ~ to!string((maxInotifyWatches * 2)));
+				} else {
+					// some other platform
+					addLogEntry("The user limit on the total number of inotify watches has been reached.");
+					addLogEntry("Please seek support from your distribution on how to increase the max number of inotify watches to at least double your existing value.");
+				}
 			}
 			if (errno() == 13) {
 				if (verboseLogging) {addLogEntry("WARNING: inotify_add_watch failed - permission denied: " ~ pathname, ["verbose"]);}