FILES = main.o phone.o
CC    =	gcc
CFLAGS	=	-g -Wall -ansi -c
#	Note that with this setup we can change from gcc compiler to g++ 
#	By altering a single line!

#	The next line is invoked with "make phone" or just "make"
#	It causing the forming of the object files and  "loads" them 
#	into the executable.
phone:  $(FILES)
	$(CC) -o phone $(FILES)

#	Although will be done automatically if needed, "make main.o" otherwise
main.o: phone.h main.c
	$(CC) $(CFLAGS) main.c

#	Illustrates the benefits of macros
phone.o:    phone.c phone.h
	$(CC) $(CFLAGS) phone.c

#	To remove unwanted *.o files
clean:	$(FILES)
		/usr/bin/rm $(FILES)

/*--------------------end of makefile--------------*/


/*********************************************************
 *
 *                  phone.h
 *
 *  Basic data structure definitions for the phone book
 *  example.
 *
 *********************************************************/

#define NAMELENGTH  20
#define PHONELENGTH 10

#ifndef TRUE
#define TRUE 1
#endif


struct phone_struct {
    char    name[NAMELENGTH];
    char    phone[PHONELENGTH];
};

void read_phone_file (FILE*);
char* get_phone_number (char*);

/*-----------------end of phone.h---------------------------------*/


/************************************************************
 *
 *                   phone.c
 *
 *  The routines in this file maintain the phone book data
 *  structure.  All access to this data structure must be
 *  through the routines in this file.
 *
 **********************************************************/

#include <stdio.h>
#include <string.h>
#include "phone.h"

/*
 *  SIZE is the length of the array used to store the
 *  phone list
 */

#define SIZE    200

/*
 *  phone_table is the array that stores the phone list.
 *  Numbers is the number of entries in the phone list.
 */

static struct phone_struct phone_table[SIZE];

static int Numbers = 0;


/*
 *  read_phone_list
 *
 *  Purpose: transfer the phone list from disk to internal storage
 *
 *  Pre-conditions: the phone list is initially empty
 *
 *  Post-conditions: the phone_table array has the contents of the
 *                   disk file
 */

void read_phone_file (FILE* fid)
{
    int n;
    int i;

    i = 0;

    while (TRUE) {

        n = fscanf(fid,"%20s %10s",
			                 &(phone_table[i].name[0]), 
			                 &(phone_table[i].phone)[0]);

        if (n < 0)
            break;

        i++;
    }

    Numbers = i;
}

/*
 *  get_phone_number
 *
 *  Purpose:  look up the name corresponding to a phone number
 *
 *  Pre-conditions: the name is in the phone list
 *
 *  Post-conditions: returns the number corresponding to the
 *                   name that was passed as a parameter
 */

char* get_phone_number (char* name)
{
    int i;

    for (i = 0; i < Numbers; i++) {
        if ( strcmp (name, phone_table[i].name) == 0 ) {
            return (phone_table[i].phone);
        }
    }

    return (NULL);
}

/*------------------end of phone.c----------------*/


/*********************************************************
 *
 *                    main.c
 *
 *  Main program for the phone number program.  The main
 *  program is responsible for all interactions with the
 *  user.  It first determines the file that the phone
 *  book is stored on and then calls read_phone_file to
 *  read the phone book.  The program then asks the user
 *  for the names of people and prints their phone numbers.
 *  The get_phone_number procedure us used to lookup a
 *  phone number given a person's name.  The phone book
 *  data structure is maintained by the routines in the
 *  phone.c file.
 *
 *******************************************************/


#include <stdio.h>
#include <string.h>
#include "phone.h"


int main (int argc, char** argv)
{
    FILE* fid;
    char name[NAMELENGTH];
    char* phone;

    if (argc != 2) {
        printf ("usage: phone phone_file\n");
        return (1);
    }

    fid = fopen (argv[1], "r");
    if (fid == NULL) {
        printf("unable to open phone file: %s\n", argv[1]);
        return (2);
    }

    read_phone_file (fid);


    while (TRUE) {

        printf("name: ");
        scanf ("%20s", &name[0]);

        if (strcmp (name, "exit") == 0)
            break;

        phone = get_phone_number(name);

        if (phone == NULL) {
            printf("sorry, no number for %s\n", name);
        } else {
            printf("the phone number for %s is %s\n", name, phone);
        }

    }

    return (0);
}

/*              sample input data file
Green	7654
Brown	6789
Yellow	4321
White	8901
Red 	3425
Pink	9012
*/