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CS321/Homework 2/time.c

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+/**
+ * Records the amount of time to run a command.
+ * Uses shared memory.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/time.h>
+#include <sys/shm.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[])
+{
+    const char *name = "v1";
+    const int SIZE = 24;
+
+    struct timeval start;
+    struct timeval end;
+    pid_t pid;
+    int shm_fd;
+    char *ptr;
+
+    if (argc == 1)
+        return 0;
+
+    shm_fd = shm_open(name, O_CREAT | O_RDWR, 0666);
+
+    if (shm_fd == -1) {
+        printf("shared memory creation failed\n");
+        return  -1;
+    }
+
+    ftruncate(shm_fd, SIZE);
+
+    ptr = (char *)mmap(0, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0);
+
+    if (ptr == MAP_FAILED) {
+        printf("memory map failed\n");
+        return -1;
+    }
+
+    pid = fork();
+
+    if (pid == 0)
+    {
+        // child
+        if (gettimeofday(&start, NULL) != 0)
+            return 0;
+
+        // Write the starting time to shared memory
+        sprintf(ptr, "%ld %ld", start.tv_sec, start.tv_usec);
+        // Execute the command
+        if (execvp(argv[1], &argv[1]) == -1) {
+            perror("execvp");
+            exit(1);
+        }
+    }
+    
+    else {
+        // Parent
+        wait(NULL);
+
+        if (gettimeofday(&end, NULL) != 0)
+            return -1;
+
+        printf("\nParent ending time = %ld sec, %ld microsec\n",end.tv_sec, end.tv_usec);
+
+        // Read the starting time from shared memory
+        long start_sec, start_usec;
+        sscanf(ptr, "%ld %ld", &start_sec, &start_usec);
+        
+        // Determine elapsed time
+        long elapsed_sec = end.tv_sec - start_sec;
+        long elapsed_usec = end.tv_usec - start_usec;
+        if (elapsed_usec < 0) {
+            elapsed_sec--;
+            elapsed_usec += 1000000;
+        }
+
+        printf("Elapsed time = %ld sec, %ld microsec\n", elapsed_sec, elapsed_usec);
+
+        shm_unlink(name);
+    }
+
+    return 0;
+}

CS321/Homework 2/zombieCode.c

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+/*
+ * ZombieCode.c
+ * This small program generates a zombie process.
+ *
+ * A zombie process is created when a process terminates,
+ * but the parent does not invoke wait(), but the parent
+ * continues to run. By not invoking wait(), the child
+ * process maintains an entry in the process entry table
+ * as well as maintaining its pid.
+ *
+ * Pretty simple to do:
+ *
+ * (1) Create a child process
+ * (2) Have the parent run for a specified amount of time.
+ *
+ * If this program is run in the background, the state of the child
+ * process illustrates it is a zombie process.
+ * (Z underneath the S field using ps)
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <sys/types.h>
+
+int main(void)
+{
+        pid_t pid;
+
+        pid = fork();
+
+        if (pid < 0) {
+                fprintf(stderr,"Unable to create child process\n");
+
+                return -1;
+        }
+        else if (pid == 0) {
+                /**
+                 * Just have the child exit
+                 * and turn into a zombie.
+                 */
+
+                return 0;
+        }
+        else {
+
+                // [FILL UP] Have the parent sleep for 15 seconds
+                sleep(15);
+
+                printf("Parent exiting\n");
+
+                return 0;
+        }
+}