From b4a3c3aeae1b04116c14426aabaed1aada178767 Mon Sep 17 00:00:00 2001
From: EdwardEisenhauer <sergiusz.warga@pwr.edu.pl>
Date: Wed, 10 Mar 2021 19:46:05 +0100
Subject: [PATCH] My code runs backward in time

---
 Topic-2/task_2_4.c | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/Topic-2/task_2_4.c b/Topic-2/task_2_4.c
index 65d2806..8c89ad3 100644
--- a/Topic-2/task_2_4.c
+++ b/Topic-2/task_2_4.c
@@ -7,51 +7,62 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <signal.h>
+#include <time.h>
 
 void parent_before_child() {
     pid_t pid;
-    printf("parent_before_child()\n");
+    printf("\nparent_before_child()\n");
     pid = fork();
     if (pid == -1) {    // If something went wrong.
         perror("Fork: ");
         exit(EXIT_FAILURE);
     }
     if (pid != 0) {     // If this is a parent process.
-        printf("I am a parent.\n");
-        kill(getpid(), SIGKILL);
+        printf("===\nI am a parent.\nMy PID is: %d\n===", getpid());
+        kill(getpid(), SIGTERM);
     } else {
         sleep(1);
-        printf("I am a child\n");   // This line will not be printed, as (usually) parent process will finish
-        // its execution in less than 1 second.
+        printf("===\nI am a child.\nMy PID is: %d\n===", getpid()); // This line will not be printed, as (usually) parent process will finish
+        // its execution in less than 1 second
     }
 }
 
 void child_before_parent() {
     pid_t pid;
-    printf("child_before_parent()\n");
+    printf("\nchild_before_parent()\n");
+    printf("PID before fork: %d\n", getpid());
     pid = fork();
     if (pid == -1) {    // If something went wrong.
         perror("Fork: ");
         exit(EXIT_FAILURE);
     }
     if (pid == 0) {     // If this is a parent process.
-        printf("I am a child.\n");
-        kill(getpid(), SIGKILL);
+        printf("===\nI am a child.\nMy PID is: %d\n===", getpid());
+        kill(getpid(), SIGTERM);
     } else {
         sleep(1);
-        printf("I am a parent.\n");
+        printf("===\nI am a parent.\nMy PID is: %d\n===", getpid());
     }
 }
 
+double time_from_exec(clock_t begin) {
+    return (double)(clock() - begin)/CLOCKS_PER_SEC;
+}
+
 int main() {
+    clock_t begin = clock();
     pid_t pid;
+    printf("%f: Grandparent process has PID: %d\n", time_from_exec(begin), getpid());
     pid = fork();
-    if (pid == 0) {
+    if (pid == 0) { // If child process
+        printf("%f: Process with PID %d will execute funs.\n", time_from_exec(begin), getpid());
         child_before_parent();
         sleep(1);
         parent_before_child();
         sleep(1);
+    } else {        // If parent process
+        printf("%f: Grandparent's child process has PID: %d\n", time_from_exec(begin), pid);
+        sleep(5);
     }
-    sleep(5);
     return 0;
 }
\ No newline at end of file