adding signal_handler

daemonize.c

@@ -13,8 +13,41 @@
 #include <signal.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <syslog.h>
 
+int flag_reconf = 0;
+
+void signal_handler(int sig){
+    /*
+    The waitpid() function suspends the current process until the child corresponding to the pid 
+    passed in the argument terminates, or until the current process receives a termination signal.
+    If the current process executes the waitpid() function and the child identified by the pid is in 
+    a zombie state, then the function returns immediately and any resources in the child are freed.
+    */
+    int status;
+    pid_t child_pid;
+    if(sig == SIGCHLD){ //Handles automatic cleanup of subprocesses created with fork()
+        // Clears ALL terminated children (cycle required if multiple signals arrive at once)
+        while ( (child_pid = waitpid(-1, &status, WNOHANG | WUNTRACED | WCONTINUED)) > 0){
+
+            if (WIFEXITED(status))
+                syslog(LOG_INFO, "child %d exited normally with code %d", child_pid, WEXITSTATUS(status));
+            else if (WIFSIGNALED(status))
+                syslog(LOG_ERR, "child %d terminated by signal %d", child_pid, WTERMSIG(status));
+            else if (WIFSTOPPED(status))
+                syslog(LOG_WARNING, "child %d stopped by signal %d", child_pid, WSTOPSIG(status));
+            else if (WIFCONTINUED(status))
+                syslog(LOG_INFO, "child %d resumed with SIGCONT", child_pid);
+
+        }
+
+    } else if(sig == SIGHUP){   //Ensures that the program does not die if you close the terminal window.
+        flag_reconf = 1;
+    }
+
+}
+
 static void skeleton_daemon()
 {
     pid_t pid;
@@ -35,9 +68,8 @@ static void skeleton_daemon()
         exit(EXIT_FAILURE);
 
     /* Catch, ignore and handle signals */
-    //TODO: Implement a working signal handler */
-    signal(SIGCHLD, SIG_IGN);
-    signal(SIGHUP, SIG_IGN);
+    signal(SIGCHLD, signal_handler);
+    signal(SIGHUP, signal_handler);
 
     /* Fork off for the second time*/
     pid = fork();
@@ -67,17 +99,42 @@ static void skeleton_daemon()
     /* Open the log file */
     openlog ("firstdaemon", LOG_PID, LOG_DAEMON);
 }
-
+/*
+for testing: 
+    1. make
+    2. ./firstdaemon
+    3. pgrep firstdaemon --> for pid
+    4. enter with a signal: kill -SIGCHLD <result_of_pgrep> or -SIGHUP
+    5. journalctl -t firstdaemon --> to see log
+*/
 int main()
 {
     skeleton_daemon();
 
     while (1)
     {
+        //for SIGHUP
+        if(flag_reconf){
+            flag_reconf = 0;
+            closelog();
+            openlog("firstdaemon", LOG_PID, LOG_DAEMON);
+            syslog(LOG_INFO, "configuration reloaded");
+        }
+
+        //to test SIGCHLD
+        pid_t child = fork();
+        if (child < 0) {
+            syslog(LOG_ERR, "fork error");
+        } else if (child == 0) {
+
+            sleep(20);
+            exit(EXIT_SUCCESS);
+        }
+
         //TODO: Insert daemon code here.
         syslog (LOG_NOTICE, "First daemon started.");
         sleep (20);
-        break;
+        //break;
     }
 
     syslog (LOG_NOTICE, "First daemon terminated.");