Assignment 1

mm.c

@@ -0,0 +1,99 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+#define debug 0
+#define SUCCESS 0
+#define FAILURE -1
+
+// 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()
+//    int n,  the length of the list
+//    char *list[], command line argument. Data starts at index 1. 
+double  mean(int n, char *list[]) {
+    int sum = 0;
+    int i;
+    for(i = 1; i < n; i++) {
+        sum +=  atoi(list[i]);
+    }
+    return (double) sum / (double)(n-1);
+}
+
+// median()
+//    int n, number of elements in list.
+//    int *list, pointer to first element of a SORTED list.
+double median(int n , int *list) {
+    if ((n-1) % 2 != 0) {
+        return (double) list[(n-1)/2];
+    }
+    else {
+        return ((double) list[((n-1)/2)-1] + (double) list[((n-1)/2)]) / 2.0;
+    }
+}
+
+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 FAILURE;
+    }
+
+    // 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 results
+    fprintf(stdout, "%s results: \n", argv[0]);
+
+    int rc = fork();
+
+    if (rc < 0) {
+        fprintf(stderr,"%s aborting: Could not fork\n", argv[0]);
+        return FAILURE;
+    }
+
+    if (rc == 0) {
+        // Child code.
+        fprintf(stdout, "Median = %f\n", median(argc,pt));
+#if debug
+    fprintf(stdout, "%s: DEBUG: rc = %d, PID = %d\n",argv[0],rc,getpid());
+#endif
+    }
+
+    if  (rc > 0) {
+        //parent code.
+        wait(NULL); // wait until child is finished.
+        fprintf(stdout,"Mean = %f\n", mean(argc,argv));
+#if debug
+    fprintf(stdout, "%s: DEBUG: rc = %d, PID = %d\n", argv[0],rc,getpid());
+#endif
+    }
+    return SUCCESS;
+}