week4

week04/ex1.c

@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+int main() {
+    clock_t pt = clock(), t1, t2;
+    int status;
+
+    printf("Main. PID: %d\nParent PID: %d\n\n", getpid(), getppid());
+
+    pid_t child1 = fork(), child2;
+    t1 = clock();
+
+    if (child1 != 0) {
+        child2 = fork();
+        t2 = clock();
+    }
+
+    if (child1 == 0) {
+        printf("Child1. PID: %d\nParent PID: %d\n", getpid(), getppid());
+        t1 = clock() - t1;
+        printf("Child1. Time took: %fms\n\n", ((double)t1)/CLOCKS_PER_SEC*1000);
+    } else if (child2 == 0) {
+        printf("Child2. PID: %d\nParent PID: %d\n", getpid(), getppid());
+        t2 = clock() - t2;
+        printf("Child2. Time took: %fms\n\n", ((double)t2)/CLOCKS_PER_SEC*1000);
+    } else {
+        pt = clock() - pt;
+        printf("Main. Time took: %fms\n\n", ((double)pt)/CLOCKS_PER_SEC*1000);
+    }
+}

week04/ex1.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+gcc ex1.c -o ex1
+./ex1

week04/ex2.c

@@ -0,0 +1,47 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+int main() {
+    srand(time(NULL));
+    FILE *out = fopen("temp.txt", "w");
+    int u[120], v[120];
+    for (int i = 0; i < 120; ++i)
+        u[i] = rand() % 100, v[i] = rand() % 100;
+
+    int n;
+    scanf("%d", &n);
+    pid_t id[10];
+    int start = -1, sz = 120 / n;
+    for (int i = 0; i < n; ++i) {
+        id[i] = fork();
+        if (id[i] == 0) {
+            start = i * sz;
+            break;
+        }
+    }
+
+    if (start != -1) {
+        int res = 0;
+        for (int i = 0; i < sz; ++i) {
+            res += u[start + i] * v[start + i];
+        }
+        fprintf(out, "%d\n", res);
+    } else {
+        int status;
+        wait(&status);
+        fclose(out);
+        int res = 0;
+        FILE *in = fopen("temp.txt", "r");
+        for (int i = 0; i < n; ++i) {
+            int a;
+            fscanf(in, "%d", &a);
+            res += a;
+        }
+        fclose(in);
+        printf("Result: %d\n", res);
+    }
+}

week04/ex2.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+gcc ex2.c -o ex2
+./ex2

week04/ex3.c

@@ -0,0 +1,16 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int main(int argc, char **argv) {
+    if (argc != 2) {
+        printf("Usage: %s [n]\n", argv[0]);
+        exit(1);
+    }
+
+    int n = atoi(argv[1]);
+    for (int i = 0; i < n; ++i) {
+        fork();
+        sleep(5);
+    }
+}

week04/ex3.sh

@@ -0,0 +1,26 @@
+#!/bin/sh
+
+gcc ex3.c -o ex3
+./ex3 3 &
+sleep 1
+
+i=0
+while [ $i -lt 3 ]
+do
+    pstree
+    sleep 5
+    i=$(( i + 1 ))
+done
+
+./ex3 5 &
+sleep 1
+
+i=0
+while [ $i -lt 5 ]
+do
+    pstree
+    sleep 5
+    i=$(( i + 1 ))
+done
+
+

week04/ex3.txt

@@ -0,0 +1,5 @@
+During the experiment, I have got in total 8 processes for n=3, and 32 processes for n=5.
+
+If we do fork() in a loop, in each iteration of a loop (but not at the same time), the number of processes increases by two (x * 2, where x is the current number of processes).
+
+That is why, in the end, the total number of processes will be 2^n.

week04/ex4.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main() {
+    while(1) {
+        printf("$ ");
+        char command[256];
+        fgets(command, 256, stdin);
+        system(command);
+    }
+}

week04/ex4.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+gcc ex4.c -o ex4
+./ex4

week04/temp.txt

@@ -0,0 +1,10 @@
+20985
+27368
+35342
+11568
+31843
+21304
+34481
+33455
+39728
+28530