Read and show some attributes of child and parent process.

Author: optiklab

multithreading/00 - Fork Processes.c

@@ -4,9 +4,10 @@
 #include <unistd.h> 
 #include <sys/wait.h> // For wait, waitpid
 
+#include "Common.h"
+
 #define PORTNUM 1500  // Port > 1024 because program will not work not as root.
 #define NUMBER_OF_PROCESSES 2
-#define EXIT_FAILURE 1
 
 // Compilation:
 // gcc -std=gnu99 "00 - Fork Processes.c" -o forkProcesses
@@ -17,33 +18,34 @@
 int main(int argc, char *argv[])
 {
     printf("Enter to main!\n");
+    printf("Creating %d of child processes...\n", NUMBER_OF_PROCESSES);
  	for (int i = 0; i < NUMBER_OF_PROCESSES; i++)
 	{
 		pid_t pid;
 		int status;
 		switch(pid=fork())
 		{
 			case -1:
-                  printf("PROC %d:", i);
-                  perror("1 Error of calling fork");
-				  exit(EXIT_FAILURE);
+				printf("PROC %d:", i);
+				perror("1 Error of calling fork");
+				exit(EXIT_FAILURE);
 			case 0:
-				  printf("PROC %d: 1 CHILD: Child process %d!\n", i, getpid());
-				  printf("PROC %d: 2 CHILD: Parent PID %d!\n", i, getppid());
-				  printf("PROC %d: 3 CHILD: Wait 10 seconds...\n", i);
-                  sleep(10);
-                  printf("PROC %d: 4 CHILD: Exit!\n", i);
-				  exit(EXIT_FAILURE);
+				printf("PROC %d: 1 CHILD: Child process %d!\n", i, getpid());
+				printf("PROC %d: 2 CHILD: Parent PID %d!\n", i, getppid());
+				printf("PROC %d: 3 CHILD: Wait 4 seconds...\n", i);
+				sleep(4);
+				printf("PROC %d: 4 CHILD: Exit!\n", i);
+				exit(EXIT_SUCCESS);
 			default:
-				  printf("PROC %d: 1 PARENT: Parent process %d!\n", i, getpid());
-				  printf("PROC %d: 2 PARENT: Child PID %d\n", i, pid);
-				  printf("PROC %d: 3 PARENT: Wait until child calls exit()...\n", i);
-				  waitpid(pid, &status, 0);
-				  printf("PROC %d: 4 PARENT: Child exit code: %d\n", i, WEXITSTATUS(status));
-				  printf("PROC %d: 5 PARENT: Exit!\n", i);
+				printf("PROC %d: 1 PARENT: Parent process %d!\n", i, getpid());
+				printf("PROC %d: 2 PARENT: My child PID %d\n", i, pid);
+				printf("PROC %d: 3 PARENT: Wait until child calls exit()...\n", i);
+				waitpid(pid, &status, 0);
+				printf("PROC %d: 4 PARENT: Child exit code: %d\n", i, WEXITSTATUS(status));
+				printf("PROC %d: 5 PARENT: Exit!\n", i);
 		}
 	}
 
     printf("Exit main!\n");
-    exit(0);
+    exit(EXIT_SUCCESS);
 }

multithreading/Common.h

@@ -1,8 +1,11 @@
 #include <sys/wait.h>
 #include <signal.h>
 
+#define EXIT_SUCCESS 0
 #define EXIT_FAILURE 1
 
+#define FAILURE -1
+
 void kill_child_handler(int sig)
 {
     int status;
@@ -36,7 +39,7 @@ void handle_child_finishing()
     struct sigaction kill_child_signal;
     kill_child_signal.sa_handler = kill_child_handler;
     sigemptyset(&kill_child_signal.sa_mask);
-    kill_child_signal.sa_flags = SA_RESTART; // Permanent handler.
+    kill_child_signal.sa_flags = SA_RESTART; // Mark handler as Permanent.
 
     if (sigaction(SIGCHLD, &kill_child_signal, 0) == -1)
     {