Created skeleton daemon and added PIDfile

CMakeLists.txt

 cmake_minimum_required(VERSION 3.25)
 project(batteryd)
-
 set(CMAKE_CXX_STANDARD 20)
 
-add_executable(batteryd src/main.cpp src/daemonutils.cpp)
+if (USE_SYSLOG)
+    add_definitions(-DUSE_SYSLOG)
+endif ()
+
+add_executable(batteryd src/daemonutils.h src/daemonutils.cpp src/main.cpp)

README.md

@@ -14,7 +14,7 @@ The tresholds and the actions to take are both configurable in `/etc/systemcshee
 ### Why?
 Why not? It was a long and rough day and around 2AM, after 5-6 beers, it seemed to be a good idea to
 write a daemon for a task I wanted, but mostly for my personal amusement.
-This is generally intended as a joke, although for me it serves real purpose.
+This is generally intended as a joke, although for me, it serves real purpose.
 I didn't want to use any 3rd party service for monitoring my battery level(s),
 because I know exactly what I want and how I want to do it and what configuration options I wish.
 Obviously this could have been done with a shell script in a cronjob, but it's not that fun.
@@ -33,6 +33,10 @@ You can also monitor your wireless keyboard and/or mouse. At this time, only one
 
 An example can be found in [batteryd.conf.example](batteryd.conf.example)
 
+### Building
+You can build this project with CMake or technically anything else you can make it work with.
+
+If you want to use `syslog` instead of a logfile in `/var/log/systemcshee/batteryd.log` then add `-DUSE_SYSLOG=1` to cmake parameters or define `USE_SYSLOG` any other way.
 
 ### License
 This project is under the [GNU General Public License v3.0](COPYING)

src/daemonutils.cpp

@@ -4,15 +4,30 @@
  * License: GNU GPL v3.0
  */
 
+#include "daemonutils.h"
+
+#ifdef USE_SYSLOG
+
+#include <syslog.h>
+
+#endif
+
 #include <cstdlib>
 #include <unistd.h>
 #include <csignal>
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <syslog.h>
 #include <cstdio>
+#include <fstream>
+#include <fcntl.h>
+#include <cstring>
 
-static void daemonize() {
+#define DEFAULT_PIDFILE_LOCATION "/var/run/systemcshee/batteryd.pid"
+
+static int pidfile = -1;
+std::ofstream *logfile_stream;
+
+void daemonize() {
     // First fork to lose parent to PID1, then create own session
     pid_t pid;
     pid = fork();
@@ -40,12 +55,59 @@ static void daemonize() {
     stdin = fopen("/dev/null", "r");
     stdout = fopen("/dev/null", "w+");
     stderr = fopen("/dev/null", "w+");
+
+    // Create PIDfile
+    // TODO: make pidfile configurable from cli options
+    char tmpstr[32];
+    pidfile = open(DEFAULT_PIDFILE_LOCATION, O_RDWR | O_CREAT, 0640);
+    if (pidfile < 0) {
+        // Cannot open pidfile, exiting
+        exit(EXIT_FAILURE);
+    }
+    // Try to acquire a lock
+    if (lockf(pidfile, F_TEST, 0) < 0) {
+        if (errno == EACCES || errno == EAGAIN) {
+            // Locked by probably another batteryd instance, exiting for now
+            // TODO: decide what to do when another instance is running
+            exit(EXIT_FAILURE);
+        }
+        // Something else went wrong, exiting
+        exit(EXIT_FAILURE);
+    }
+    // Save the PID
+    sprintf(tmpstr, "%d\n", getpid());
+    write(pidfile, tmpstr, strlen(tmpstr));
+}
+
+void setup_logging() {
+#ifdef USE_SYSLOG
+    openlog("systemcshee-batteryd", LOG_PID, LOG_DAEMON);
+//#else
+    logfile_stream = new std::ofstream();
+    logfile_stream->open("/var/log/systemcshee/batteryd.log", std::ios_base::out | std::ios_base::app);
+    logfile_stream->write("Batteryd started", 100);
+    logfile_stream->close();
+#endif
+}
+
+static void signal_handler(int signal) {
+    if (signal == SIGINT || signal == SIGTERM) {
+
+    }
+}
+
+void shutdown() {
+    logfile_stream->close();
+    delete logfile_stream;
+    close(pidfile);
 }
 
 static void setup() {
+
+
     signal(SIGCHLD, SIG_IGN);
     signal(SIGHUP, SIG_IGN);
 
     /* Open the log file */
-    openlog("systemcshee-batteryd", LOG_PID, LOG_DAEMON);
+
 }
\ No newline at end of file

src/daemonutils.h

+/*
+ * Created by: Cshee, 2023-02-09
+ * Project: SystemCshee / batteryd
+ * License: GNU GPL v3.0
+ */
+
+#ifndef BATTERYD_DAEMONUTILS_H
+#define BATTERYD_DAEMONUTILS_H
+
+void daemonize();
+
+void setup_logging();
+
+void shutdown();
+
+#endif //BATTERYD_DAEMONUTILS_H

src/main.cpp

-#include <iostream>
+#include <csignal>
+#include "daemonutils.h"
 
 int main() {
-    std::cout << "Hello, World!" << std::endl;
+    daemonize();
+    setup_logging();
+
+    while (true) {
+        sleep(20);
+        break;
+    }
+
+    shutdown();
+
     return 0;
 }