The C language implements the address book

This article shares the specific code of C language address book for your reference. The specific content is as follows

The functions realized include:

1. Initialize the address book;
2. Add an entry to the address book;
3. Delete the specified entry in the address book;
4. Find specific entries in the address book according to specified rules;
5. Print all the information in the address book;
6. Modify the specified entry in the address book;
7. Destroy the address book;
8. Save the address book contents in a file;
Load the contents of the file back into memory.

**Addr_Book.h**

#pragma once
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define NAME_SIZE 200 
#define PHONE_SIZE 200 
#define ADDR_SIZE 200

typedef struct PersonInfo {
  char name[NAME_SIZE];
  char phone[PHONE_SIZE];
  char addr[ADDR_SIZE];
} PersonInfo;

#define FILE_PATH "./data.txt"

enum {
  DISPLAY = 1,
  ADD = 2,
  ERASE = 3,
  FIND = 4,
  MODIFY = 5,
  EXIT = 0
};

typedef struct AddrBook {
  PersonInfo* data;// content 
  size_t size; // Number of contacts 
  size_t capacity; // Address book capacity 
} AddrBook;


/**
* @brief  Initialize the address book 
*
* @param addr_book
*/
void AddrBookInit(AddrBook* addr_book);

/**
* @brief  Add an entry to the address book 
*
* @param addr_book
*/
void AddrBookAdd(AddrBook* addr_book);

/**
* @brief  Deletes the specified entry in the address book 
*
* @param addr_book
*/
void AddrBookErase(AddrBook* addr_book);

/**
* @brief  Finds a specific entry in the address book by following the specified rule 
*
* @param addr_book
*/
void AddrBookFind(AddrBook* addr_book);

/**
* @brief  Print all the information in the address book 
*
* @param addr_book
*/
void AddrBookDisplay(AddrBook* addr_book);

/**
* @brief  Modifies the specified entry in the address book 
*
* @param addr_book
*/
void AddrBookModify(AddrBook* addr_book);

/**
* @brief  Destroy address book 
*
* @param addr_book
*/
void AddrBookDestroy(AddrBook* addr_book);

/**
* @brief  Save the address book contents in a file 
*
* @param addr_book
*/
void AddrBookSave(AddrBook* addr_book);

/**
* @brief  Loads the contents of the file back into memory .
*
* @param addr_book
*/
void AddrBookLoad(AddrBook* addr_book);

**Addr_Book.c**

#define _CRT_SECURE_NO_WARNINGS 1

#include "Addr_Book.h"

// Print address book 
void AddrBookDisplay(AddrBook* addr_book){ 
  if (addr_book == NULL){
    return;
  }
  printf("\n==================== The address book =========================\n");
  printf("|    The name    |    number    |    address    |\n");
  printf("|----------------|---------------|----------------|\n");
  size_t i = 0;
  for (; i < addr_book->size; ++i){
    printf("|   %s   |   %s   |   %s   |\n", 
      addr_book->data[i].name, addr_book->data[i].phone, addr_book->data[i].addr);
    printf("|----------------|---------------|----------------|\n");
  }
}

// Initialize the address book 
void AddrBookInit(AddrBook* addr_book){ 
  if (addr_book == NULL){
    return ;
  }
  addr_book->size = 0;
  addr_book->capacity = 1;
  addr_book->data = (PersonInfo*)malloc(sizeof(PersonInfo)*addr_book->capacity);
}

// Expand the memory 
void AddrBookRelloc(AddrBook* addr_book){
  if (addr_book == NULL){
    return;
  }
  addr_book->capacity = addr_book->capacity * 2 + 1;// There is not enough memory, expand the capacity 
  PersonInfo* new_data = (PersonInfo*)malloc(sizeof(PersonInfo)*addr_book->capacity);// Open up new space sizes 
  size_t i = 0;
  for (; i < addr_book->size; ++i){
    new_data[i] = addr_book->data[i];// Assign old memory to new memory 
  }
  free(addr_book->data);// Free up old memory 
  addr_book->data = new_data;
}

// Add contacts 
void AddrBookAdd(AddrBook* addr_book){ 
  if (addr_book == NULL){
    return;
  }
  if (addr_book->size >= addr_book->capacity){ // There is not enough memory to expand memory 
    AddrBookRelloc(addr_book);
  }
  size_t cur = addr_book->size;
  ++addr_book->size;
  printf(" Add contacts \n");
  printf(" Enter name: ");
  scanf("%s", addr_book->data[cur].name);
  printf(" Input number: ");
  scanf("%s", addr_book->data[cur].phone);
  printf(" Input address: ");
  scanf("%s", addr_book->data[cur].addr);
  printf(" Add the end !\n");
}

// Delete the specified contact 
void AddrBookErase(AddrBook* addr_book){ 
  if (addr_book == NULL){
    return;
  }
  char delete_name[200] = {0};
  printf(" Enter the name of the contact to delete: ");
  scanf("%s", &delete_name);
  size_t i = 0;
  for (; i <addr_book->size;++i){
    if (strcmp(addr_book->data[i].name, delete_name)){
      free(addr_book->data);
      addr_book->size--;
      printf(" Has been deleted! ");
    }
    else{
      printf(" Delete failed, please re-enter the contact! ");
    }
  }
}

// Save the content 
void AddrBookSave(AddrBook* addr_book){ 
  FILE* fp = fopen(FILE_PATH, "w");
  if (fp == NULL){
    printf(" Failed to open file !\n");
    return;
  }
  size_t i = 0;
  for (; i < addr_book->size; ++i){
    fprintf(fp, "|   %s   |   %s   |   %s   |\n",
      addr_book->data[i].name, addr_book->data[i].phone, addr_book->data[i].addr);
  }
  fclose(fp);
}

// Find contacts by name 
void AddrBookFind(AddrBook* addr_book){  
  if (addr_book == NULL){
    return;
  }
  char delete_name[200] = { 0 };
  printf(" Enter the name of the contact sought: ");
  scanf("%s", &delete_name);
  size_t i = 0;
  for (; i <addr_book->size; ++i){
    if (strcmp(addr_book->data[i].name, delete_name)){
      printf(" Found, the contact information is: Name: %s, Number: %s, Address: %s\n",
        addr_book->data[i].name, addr_book->data[i].phone, addr_book->data[i].addr);    
    }
    else{
      printf(" This person doesn't exist! \n");
    }
  }
}

// Modify contact information 
void AddrBookModify(AddrBook* addr_book){
  if (addr_book == NULL){
    return;
  }
  char name[200] = { 0 };
  printf(" Enter the name of the contact to be modified: ");
  scanf("%s", &name);
  size_t i = 0;
  for (; i < addr_book->size; ++i)
  {
    if (strcmp(addr_book->data[i].name, name) == 0)
    {
      printf(" This is the first %lu Contact person: \n", i + 1);          
      printf(" This person's information is: \n  Name: %s , Telephone: %s , Address: %s\n",
        addr_book->data[i].name,
        addr_book->data[i].phone,
        addr_book->data[i].addr);
    }
  }
  size_t num = 0;
  printf(" Enter the contact number you want to change: ");       
  scanf("%lu", &num);
  char name2[200];
  char phone[200];
  char addr[200];
  printf(" Please enter your new name: ");
  scanf("%s", name2);
  strcpy(addr_book->data[num - 1].name, name2);
  printf(" Please enter your new phone number: ");
  scanf("%s", phone);
  strcpy(addr_book->data[num - 1].phone, phone);
  printf(" Please enter the new address: ");
  scanf("%s", addr);
  strcpy(addr_book->data[num - 1].addr, addr);
  printf(" Modified successfully! \n");
  return;

}

// Destroy address book 
void AddrBookDestroy(AddrBook* addr_book){
  if (addr_book == NULL)            
  {
    printf("addr_book is null\n");
    return;
  }
  else
  {
    addr_book->size = 0;
    addr_book->capacity = 0;
    free(addr_book->data);
    printf(" Destroy successfully! \n");
  }

}

// Loads the contents of the file back into memory 
void AddrBookLoad(AddrBook* addr_book){
  if (addr_book = NULL){
    printf(" The address book is empty! \n");
    return;
  }
  FILE* fp = fopen(FILE_PATH,"r");
  if (fp = NULL){
    printf(" Failed to open file !\n");
    return;
  }
  while (!feof(fp)){
    if (addr_book->size >= addr_book->capacity){
      AddrBookRelloc(addr_book);
    }
    size_t cur = addr_book->size;
    fscanf(fp, "%s%s%s\n", addr_book->data[i].name, addr_book->data[i].phone, addr_book->data[i].addr);
    addr_book->size++;
  }
  fclose(fp);
}



//===============
// The following is the test code 
//===============

void menu(){
  AddrBook addr_book;
  AddrBookInit(&addr_book);
  AddrBookLoad(&addr_book);

  while (1){
    printf("============1. Print address book =============\n");
    printf("============2. Add contacts =============\n");
    printf("============3. Delete contacts =============\n");
    printf("============4. Find contacts =============\n");
    printf("============5. Modify contact =============\n");
    printf("============6. Destroy address book =============\n");
    printf("============0. Exit address book =============\n");
    int choice = 0;
    printf(" Please enter the required functions: ");
    scanf("%d", &choice);
    switch (choice){
    case DISPLAY:
      AddrBookDisplay(&addr_book);
      break;
    case ADD:
      AddrBookAdd(&addr_book);
      AddrBookSave(&addr_book);
      break;
    case ERASE:
      AddrBookErase(&addr_book);
      break;
    case FIND:
      AddrBookFind(&addr_book);
      break;
    case MODIFY:
      AddrBookModify(&addr_book);
      AddrBookSave(&addr_book);
      break;
    case DESTROY:
      AddrBookDestroy(&addr_book);
      break;
    case EXIT:
      printf(" Quit the address book! \n");
      break;
    default:
      printf(" Please enter the correct selection: ");
      break;
    }
  }
}

int main(){
  menu();
  return 0;
}