prog1.c

#include <stdio.h>
#include <stdlib.h>

extern int fn1arg(int);     /* the extern keyword informs the compiler the function is defined outside this file */
extern int fn1argB(int);
extern int fn2args(int *, int *);
extern int fn3args(int *);
extern int fn6args(int, int, int, int, int, int);
extern int fn8args(int *, char **);

int main(int argc, char **argv) {
  if (argc >= 2 && argc <= 9) {
    int numInts = argc - 1;            /* var to hold number of integers passed */
    int arr[numInts];                  /* create array to hold integers passed on command-line */
    for (int i = 0; i < numInts; i++)  /* load up the array of integers */
      arr[i] = atoi(argv[i+1]);        /* convert input string to int */
    switch (numInts) {                 /* call one or more functions based on number of integers passed */
      case 1:
        fprintf(stdout, "%d", fn1arg(arr[0]));
        fprintf(stdout, " = fn(%d)  <== negate\n", arr[0]);
        fprintf(stdout, "%X", fn1argB(arr[0]));
        fprintf(stdout, " = fn(%d)  <== decrement\n", arr[0]);
        break;
      case 2: 
        fn2args(&arr[0], &arr[1]);
        fprintf(stdout, "%d, %d", arr[0], arr[1]);
        fprintf(stdout, " = fn(%d, %d)  <== sort\n", atoi(argv[1]), atoi(argv[2]));
        break;
      case 3:
        fprintf(stdout, "%X", fn3args(arr));
        fprintf(stdout, " = fn(%d, %d, %d)  <== ceil((l * w * h) / 3)\n", arr[0], arr[1], arr[2]);
        break;
      case 6:
        fprintf(stdout, "%d", fn6args(arr[0], arr[1], arr[2], arr[3], arr[4], arr[5]));
        fprintf(stdout, " = fn(%d, %d, %d, %d, %d, %d)  <== length of line in 3D space\n", arr[0], arr[1], arr[2], arr[3], arr[4], arr[5]);
        break;
      case 8:                          /* ';' added to avoid error that occurs when a declaration immediatly follows a label */
        fprintf(stdout, "%d", fn8args(&argc, argv)); /* need to access arguments through argv array */
        fprintf(stdout, " = fn(%d, %d, %d, %d, %d, %d, %d, %d)", arr[0], arr[1], arr[2], arr[3], arr[4], arr[5], arr[6], arr[7]);
        fprintf(stdout, "  <== sum of command-line arguments' ASCII values\n");
        break;
      default:
        break;
    }
  } else {
    fprintf(stderr, "Error: expecting 1 to 8 argument(s) on command-line\n");
    return 1;
  }
  return 0;
}