Assignment 1 Yucheng Liu

mm.c

@@ -0,0 +1,100 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+#define debug 0
+
+// Comparison function for qsort()
+int numcmp (const void *a, const void *b) {
+    int x = *((int*) a);
+    int y = *((int*) b);
+    if (x > y) return 1;
+    if (x < y) return -1;
+    return 0;
+}
+
+// Mean() function to calculate the mean
+double mean(int *num, int length) {
+    // Initialize sum
+    double sum = 0;
+    // Using a for loop to add all the numbers to sum
+    for (int i=0; i<length; i++)
+        sum += num[i];
+    // Return the mean
+    return sum/length;
+}
+
+// Median() function to calculate the median
+double median(int *num, int length) {
+    // If the array length is even
+    if (length%2 == 0)
+        // Return the average of the two median numbers
+        return (num[length/2-1] + num[length/2]) / 2.0;
+    // If the array length is odd
+    else
+        // Return the median
+        return num[length/2];
+}
+
+int main(int argc, char *argv[]) {
+
+    int i, length, *pt;
+
+    // Check for proper usage
+    if (argc < 2) {
+        fprintf(stderr, "%s: Aborting, not enough arguments.\n", argv[0]);
+        return (-1);
+    }
+
+    // Determine amount of numbers from argc
+    length = argc - 1;
+#if debug
+    fprintf(stderr, "%s: DEBUG: %d numbers were passed.\n", argv[0], length);
+#endif
+
+    // Allocate memory for array of number (and error check)
+    if ((pt = malloc(length * sizeof(int))) == NULL) {
+        fprintf(stderr, "%s: Could not allocate memory.\n", argv[0]);
+    }
+
+    // Read numbers into array
+    for (i = 0; i < length; i++) {
+        pt[i] = (int) strtol(argv[i+1], NULL, 10);
+    }
+
+    // Sort numbers
+    qsort(pt, length, sizeof(int), numcmp);
+
+    // Print out numbers
+    fprintf(stdout, "%s: Sorted output is: \n", argv[0]);
+    for (i=0; i<length; i++) {
+        fprintf(stdout, "%d ", pt[i]);
+    }
+    fprintf(stdout, "\n%s: FIN. \n", argv[0]);
+
+    // Make fork(), have the parent call mean() and child call median()
+    int rc = fork();
+
+    if (rc < 0) {
+        fprintf(stderr, "Fork Failed!\n");
+        exit(0);
+    } else if (rc == 0) {
+        // Child call median()
+        double child = median(pt, length);
+        // Child process should print the results of median()
+        fprintf(stdout, "This is child processing (pid:%d)\n", (int)getpid());
+        fprintf(stdout, "The median value is %f\n", child);
+    } else if (rc > 0) {
+        // Parent call mean()
+        double parent = mean(pt, length);
+        // Wait for child process
+        int wc = wait(NULL);
+        printf("Waiting for child process (wc:%d)\n", wc);
+        // Parent process should print the results of mean()
+        fprintf(stdout, "This is parent processing (pid:%d)\n", (int)getpid());
+        fprintf(stdout, "The mean value is %f\n", parent);
+    }
+
+    return 0;
+}