Log: Log to syslog if syslog.h is found

Makefile

@@ -156,6 +156,9 @@ else
 	LTO := $(THREADS)
 endif
 
+#? Look for syslog.h
+override ADDFLAGS += $(strip $(shell echo "#include <syslog.h>\nint main() {}" | $(CXX) -o /dev/null -x c++ - >/dev/null 2>&1 && echo "-DHAVE_SYSLOG"))
+
 #? The Directories, Source, Includes, Objects and Binary
 SRCDIR		:= src
 INCDIRS		:= include $(wildcard lib/**/include)

src/btop_log.cpp

@@ -7,6 +7,10 @@
 #include <mutex>
 #include <string>
 
+#if defined(HAVE_SYSLOG)
+	#include <syslog.h>
+#endif
+
 #include <fmt/core.h>
 #include <fmt/ostream.h>
 
@@ -44,11 +48,25 @@ namespace Logger {
 	void set(const string& level) { loglevel = v_index(log_levels, level); }
 
 	void log_write(const size_t level, const std::string_view msg) {
-		if (loglevel < level or logfile.empty()) {
+		if (loglevel < level) {
 			return;
 		}
 		atomic_lock lck(busy, true);
 		lose_priv neutered{};
+
+#if defined(HAVE_SYSLOG)
+		int status = LOG_DEBUG;
+		switch (level) {
+			case 1: status = LOG_ERR; break;
+			case 2: status = LOG_WARNING; break;
+			case 3: status = LOG_INFO; break;
+			case 4: status = LOG_DEBUG; break;
+		}
+		syslog(status, msg.data());
+#else
+		if (logfile.empty()) {
+			return;
+		}
 		std::error_code ec;
 		try {
 			if (fs::exists(logfile) and fs::file_size(logfile, ec) > 1024 << 10 and not ec) {
@@ -79,5 +97,6 @@ namespace Logger {
 			logfile.clear();
 			throw std::runtime_error(fmt::format("Exception in Logger::log_write() : {}", e.what()));
 		}
+#endif
 	}
 } // namespace Logger