Reworked Common part: definitions mobed to separate Defs.h, only useful common methods are in Common.h. Added error handlers to have proper error validation (TODO work more on it).

Author: Anton Yarkov

multithreading/00 - Fork Processes.c renamed to multithreading/00 - Fork N Processes.c

@@ -1,51 +1,49 @@
-#include <stdio.h>
-#include <stdlib.h>
-#include <fcntl.h>
-#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
-
-// Compilation:
-// gcc -std=gnu99 "00 - Fork Processes.c" -o forkProcesses
-
-// Task:
-// Use fork to create a child process.
-
-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);
-			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 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: 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(EXIT_SUCCESS);
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h> 
+
+#include "Common.h"
+
+#define NUMBER_OF_PROCESSES 2
+
+// Compilation:
+// gcc -std=gnu99 "00 - Fork N Processes.c" -o forkProcesses
+
+// Task:
+// Use fork to create a child process.
+
+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);
+			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 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: 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(EXIT_SUCCESS);
 }

multithreading/01 - Fork Processes And End Differently.c

@@ -0,0 +1,94 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "Common.h"
+
+// Compilation:
+// gcc -std=gnu99 "01 - Fork Processes And End Differently.c" -o forkEndProcesses
+
+// Task:
+// Use fork to create a child processes, which stop working with different reasons.
+
+void display_status(pid_t pid, int status)
+{
+    if (pid != 0)
+        printf("Process %d: ", (long)pid);
+    if (WIFEXITED(status))
+    {
+        printf("Exit code: %d\n", WEXITSTATUS(status));
+    }
+    else
+    {
+        char *desc;
+        char *signame = errsymbol("signal", WTERMSIG(status), &desc); // 301
+
+        if (desc != NULL && desc[0] == '?')
+            desc = signame;
+
+        if (signame != NULL && signame[0] == '?')
+            printf("Signal #%d", WTERMSIG(status));
+        else
+            printf("%s", desc);
+
+        if (WCOREDUMP(status))
+            printf(" - memory dump reset");
+
+        if (WIFSTOPPED(status))
+            printf(" (paused)");
+        
+        printf("\n");
+    }
+}
+
+static bool wait_and_display(void)
+{
+    pid_t wpid;
+    int status;
+    ec_neg1( wpid = waitpid(-1, &status, 0));
+    display_status(wpid, status);
+    return true;
+
+EC_CLEANUP_BGN
+    return false;
+EC_CLEANUP_END
+}
+
+int main(int argc, char *argv[])
+{
+    printf("Enter to main!\n");
+    pid_t pid;
+
+    // Case 1: explicit call _exit.
+    if (fork() == 0)
+    {
+        _exit(123); // Child.
+    }
+    ec_false(wait_and_display()); // Parent.
+
+    // Case 2: fail stop.
+    if (fork() == 0)
+    {
+        int a, b = 0; // Child.
+        a = 1 / b; // Divide by zero
+        _exit(EXIT_SUCCESS);
+    }
+    ec_false(wait_and_display()); // Parent.
+
+    // Case 3: signal.
+    if ((pid=fork()) == 0)
+    {
+        sleep(100);
+        _exit(EXIT_SUCCESS);
+    }
+    ec_neg1(kill(pid, SIGHUP));
+    ec_false(wait_and_display()); // Parent
+
+    printf("Exit main!\n");
+    exit(EXIT_SUCCESS);
+
+EC_CLEANUP_BGN
+    exit(EXIT_FAILURE);
+EC_CLEANUP_END
+}

multithreading/01 - Env Vars.c renamed to multithreading/02 - Env Vars.c

@@ -9,7 +9,7 @@ extern char ** environ; // Global variable availble to any process for read/writ
 #define OVERWRITE 1
 
 // Compilation:
-// gcc -std=gnu99 "01 - Env Vars.c" -o envVars
+// gcc -std=gnu99 "02 - Env Vars.c" -o envVars
 
 // Task:
 // Read, write environment variables.

multithreading/02 - Parent Process Die.c

@@ -0,0 +1,66 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h> 
+
+#include "Common.h"
+
+// Compilation:
+// gcc -std=gnu99 "03 - Parent Process Die.c" -o parentDie
+
+// Task:
+// Use fork to create a child process. Emulate parent process died and Parent PID should become Init (1) or some other?
+
+const char* get_process_name_by_pid(const int pid)
+{
+    char* name = (char*)calloc(1024,sizeof(char));
+    if(name)
+    {
+        sprintf(name, "/proc/%d/cmdline",pid);
+        FILE* f = fopen(name,"r");
+        if(f)
+        {
+            size_t size;
+            size = fread(name, sizeof(char), 1024, f);
+            if(size>0)
+            {
+                if('\n'==name[size-1])
+                {
+                    name[size-1]='\0';
+                }
+            }
+            fclose(f);
+        }
+    }
+    return name;
+}
+
+int main(int argc, char *argv[])
+{
+    printf("Enter to main!\n");
+    printf("Create 1 child process...\n");
+    pid_t pid;
+    int status;
+    switch(pid=fork())
+    {
+        case -1:
+            perror("1 Error of calling fork");
+            exit(EXIT_FAILURE);
+        case 0:
+            printf("1 CHILD: Child process %d!\n", getpid());
+            printf("2 CHILD: Parent PID %d!\n", getppid());
+            printf("3 CHILD: Wait 3 seconds...\n");
+            sleep(3);
+            pid_t ppid = getppid();
+            printf("4 CHILD: Looks like PARENT died! What is my parent pid? %d\n", ppid); // TODO Find Parent Process Name.
+            printf("5 CHILD: My parent now is: %s\n", get_process_name_by_pid(ppid)); // TODO Find Parent Process Name.
+            printf("6 CHILD: Wow! Cool! Exit!\n");
+            exit(EXIT_SUCCESS);
+        default:
+            printf("1 PARENT: Parent process %d!\n", getpid());
+            printf("2 PARENT: Child PID %d\n", pid);
+            printf("3 PARENT: Wait 2 seconds...\n");
+            sleep(2);
+            printf("4 PARENT: Dying... bye-bye child process!\n");
+    }
+}