Lab Assignment

mm.c

@@ -0,0 +1,81 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.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;
+}
+
+// Function to calculate the mean of a vector
+int mean (int *v, int length) {
+    int i;
+    int sum = 0;
+    for(i = 0; i < length; i++) {
+        sum = sum + v[i];
+    }
+    return sum/length;
+}
+
+int median (int *v, int length) {
+    if (length%2 == 1)
+        return v[(length/2)];
+    else
+        return ((v[(length/2)-1]+v[(length)/2])/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);
+
+    int rc = fork();
+    if (rc == -1) {
+        // could not fork another process
+        fprintf(stdout, "Fork failed.\n");
+    exit(-1);
+    } else if (rc == 0) { // child runs median:
+        int med = median(pt, length);
+        fprintf(stdout, "Median = %d \n", med);
+    } else if (rc > 0) { // parent runs mean:
+        wait(NULL); // waits until child has finished
+        int avg = mean(pt, length);
+        fprintf(stdout, "Mean = %d ", avg);
+
+    }
+
+    fprintf(stdout, "\n%s: FIN. \n", argv[0]);
+
+    return 0;
+}