Overview
==========

Command Line arguments (using getopt)
Header Files
Makefiles

Homework 3
	The Game
	The board
	Wining/evaluation


Command line arguments
======================

The arguments are passed to the program as an array 
of strings.

The 0 argument is always the name of the program. So argument 1
is array position 1.

Example:
void main(int argc, char **argv)
{
   int cnt;
   printf ("I was invoked as %s\n", argv[0]);

   printf ("My arguments were:\n");   
   for (cnt=1; cnt < argc; cnt++)
     printf ("\t%d : %s\n", cnt, argv[cnt]);
}



Most programs take options like

 $ prog  -v 1 txtfile

But options are a pain...
   1.  See if the argument begins with -
   2.  Decode option (plus arguments to options)

   char *filename;
   for (cnt=1; cnt < argc; cnt++){
	char *opt = argv[cnt];
        if (opt[0] == '-') {
	  switch (opt[1]) {
	  case 's':  size = atoi (argv[cnt+1]); cnt++; break
          }
        }else { 
           filename = argv[cnt];
        }
    }        
	
     printf ("\t%d : %s\n", cnt, argv[cnt]);



Simpler way
------------

Do 'man -3C getopt' to this explained fully

#include <stdlib.h>

main(int argc, char **argv)
{
  while ((c = getopt(argc, argv, "v:")) != EOF)
    switch (c){
    case 'b': verbose = atoi (optarg);
      break;
    default:
      fprintf (stderr, "usage: prog [-v verbose_lvel] textfile\n");
      exit (0);
    }

   printf ("argument was %s\n", argv[optind]);
}





Header Files
=============


Split your code into modules including variable + functions

Why?
1.   Modularity (easier to understand big picture)
2.   Reuse (can copy code from one homework to another)


Ex.   Put all the functions that work on a board in one place (board.c)


board.c
--------

typedef struct board {
   int *bins;
   int player;
   int terminal;
} Board;


Board *alloc_board(int bins) { ..}
void  free_board (Board*){ .. }

void board_copy (Board *to, Board *from) { ... }


>>Now write a main.c that uses those function


main.c
-------

main() {

  Board *b = alloc_board (13) 

  ...
}

>>But we need to declare the functions
  --->could just copy all the suff?)
  --->Why is this not a good idea?

>>Make a header file!

board.h
-------
#ifndef BOARD_H
#define BOARD_H

typedef struct board {
   int *bins;
   int player;
   int terminal;
} Board;


Board *alloc_board(int bins);
void  free_board (Board*);
void  board_copy (Board *to, Board *from);

#endif  /* BOARD_H */


>> Now we add the line

#include "board.h"    (why "? --  <> are for system includes "" are for yours)

>> to both board.c and main.c -- Each "sees" the exact same solution.

--->  Why did I put ifdef's around the header file?


Makefile
---------

Compiling multiple files

gcc -c board.c
gcc -c main.c
gcc -o mancala main.o board.o

After editing board.c you forget to recompile 

Makefile
--------

# Board depends on board.o and main.o  
board  : board.o main.o
	gcc -o mancala main.o board.o

# 
board.o : board.c board.h
	gcc -c board.c

main.o : main.c board.h
	gcc -c main.c





>> Run by typing
   % make


Homework 3