Add lab 1

lab1/demos/chdir.c

@@ -0,0 +1,14 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <linux/limits.h>
+
+int main(void) {
+    char s[PATH_MAX];
+
+    // printing current working directory
+    printf("%s\n", getcwd(s, 100));
+    // using the command
+    chdir("..");
+    // printing current working directory after chdir is executed
+    printf("%s\n", getcwd(s, 100));
+}

lab1/demos/execve.c

@@ -0,0 +1,10 @@
+#include <stdio.h>
+#include <unistd.h>
+
+int main(void) {
+    char *args[] = {"fork", NULL};
+
+    execve("fork", args, NULL);
+
+    printf("End of execve\n");
+}

lab1/demos/exit1.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+#include <unistd.h>
+
+int main(void) {
+    printf("start of program\n");
+    _exit(3);
+    printf("End of program\n");
+}

lab1/demos/exit2.c

@@ -0,0 +1,13 @@
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdio.h>
+
+int main(void) {
+    for (int i = 0; i < 5; i++) {
+        if (fork() == 0) {
+            printf("Child %d with pid %d\n", i, getpid());
+            _exit(0);
+        }
+    }
+    printf("hello\n");
+}

lab1/demos/fork.c

@@ -0,0 +1,9 @@
+#include <unistd.h>
+#include <stdio.h>
+
+int main(void) {
+    fork(); // 2
+    fork(); // 4
+    fork(); // 8
+    printf("hello\n");
+}

lab1/demos/kill.c

@@ -0,0 +1,19 @@
+#include <signal.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <time.h>
+
+int main(void) {
+    int pid = fork();
+
+    if (pid == 0) {
+        printf("Child with pid %d\n", getpid());
+        while (1) {
+            printf("*");
+        }
+    } else {
+        sleep(1);
+        kill(pid, SIGKILL);
+        printf("\nParent killed pid %d with signal %d\n", pid, SIGKILL);
+    }
+}

lab1/demos/leak.c

@@ -0,0 +1,6 @@
+#include <stdlib.h>
+
+int main(void) {
+    int *p = malloc(64);
+    (void) p;
+}

lab1/demos/timing.c

@@ -0,0 +1,30 @@
+#include <sys/times.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+int main(void) {
+    struct tms start_times;
+    struct tms cease_times;
+
+    times(&start_times);
+
+    int pid = fork();
+
+    if (pid == 0) {
+        printf("This is a child process!\n");
+
+        for (int i = 0; i < 300000; i += 1) {
+            printf("Got a number %d\n", i);
+        }
+        _exit(1);
+    }
+
+    waitpid(pid, NULL, 0);
+    times(&cease_times);
+
+    printf("  user time: %lf\n", (double) (cease_times.tms_utime - start_times.tms_utime) / sysconf(_SC_CLK_TCK));
+    printf("system time: %lf\n", (double) (cease_times.tms_stime - start_times.tms_stime) / sysconf(_SC_CLK_TCK));
+    printf("  user time: %lf\n", (double) (cease_times.tms_cutime - start_times.tms_cutime) / sysconf(_SC_CLK_TCK));
+    printf("system time: %lf\n", (double) (cease_times.tms_cstime - start_times.tms_cstime) / sysconf(_SC_CLK_TCK));
+}

lab1/demos/wait.c

@@ -0,0 +1,21 @@
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdio.h>
+
+int main(void) {
+    for (int i = 0; i < 5; i++) {
+        int f = fork();
+
+        if (f == 0) {
+            printf("Child %d with pid %d\n", i, getpid());
+            _exit(0);
+        }
+    }
+
+    while (wait(NULL) > 0);  // This waits until all children are terminated
+    // while (waitpid(-1, NULL, 0) > 0);  // Same effect
+
+    printf("parent\n");
+    return 0;
+}

lab1/zombies.c

@@ -0,0 +1,36 @@
+// Write a program that creates a zombie, and then call system() from stdlib.h
+// (for executing a command from within a program) to execute the ps(1) command
+// to verify that the process is a zombie.
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <signal.h>
+
+void create_zombie() {
+    int pid = fork();
+
+    if (pid == 0) {
+        sleep(100000);
+    } else {
+        _exit(0);
+    }
+}
+
+void get_ps(int pid) {
+    char spid[1000];
+    sprintf(spid, "ps aux | awk '$2 == %d { print }'", pid);
+    system(spid);
+}
+
+
+int main(void) {
+    int pid = fork();
+
+    if (pid == 0) {
+        create_zombie();
+    } else {
+        get_ps(pid);
+    }
+
+    return -1;
+}