How to check a struct to see if its empty?

[yawbiney]

Hi people, I am a beginner C learner and I'm having a bit of trouble checking a structure to see if its empty or not.
I am writing a program for a phonebook/contact book and I have everything working actually but I want my program to check all arrays in each structure, and if they are empty, it prints "No contacts in your phonebook" when the user prompts it by pressing 2. I tried using an if statement to check if all arrays are NULL, then it should print the message but its not, thus indicating that they aren't NULL or empty. I say that because the program prints the alternate (else statement, which is empty spaces). Is there a way I can fix this or do it simpler. Any help would be appreciated. Thanks and codes is below.

#include <stdio.h>
typedef struct{
char name1[15];
char name2[15];
char ph_number[15];
char email[25];
}contact;
int select1,select2,contact_checker,contact_print,a;
void menu();
void contact_check();
contact friend1[3];

main()
{

menu();

switch (select1)
{

case 1:
{
do{
    printf ("First name\n");
    scanf  ("%s", friend1[a].name1);
    printf ("\nLast name\n");
    scanf  ("%s", friend1[a].name2);
    printf ("\nPhone number\n");
    scanf  ("%s", friend1[a].ph_number);
    printf ("\nE-mail\n");
    scanf  ("%s", friend1[a].email);
    a++;
    menu();}while (select1!=2);
break;
}

case 2:
    contact_check();
    break;}
contact_check();

}

void menu()
{   printf("\t\t\tPhonebook\n");
    printf("\t\t\t=========\n");
    printf("1:New contact\n2:Contact list\n");
    scanf ("%d", &select1);
}
void contact_check()
{for (contact_checker=0;contact_checker<3;contact_checker++)
if ((friend1[contact_checker].name1==NULL)&&(friend1[contact_checker].name2==NULL)&&(friend1[contact_checker].ph_number==NULL)&&(friend1[contact_checker].email==NULL))
{printf ("No contacts in your phonebook");
}else{for (contact_print=0;contact_print<3;contact_print++)
    {   printf ("\n%s %s\n", friend1[contact_print].name1,friend1[contact_print].name2);
        printf ("%s\n", friend1[contact_print].ph_number);
        printf ("%s\n", friend1[contact_print].email);}
    }
    }

[teo236]

That's because not always all the variables are initiated with a value of 0 or NULL. So you must start your code initiating all the variables of your struct as 0 or NULL, or the value that you want. In your case, when you receive an empty input, it will initiate your array as "\0", something different from null. For that I recommend you to initiate your arrays like this:

array[0]='\0';

and check if its empty like this:

if(array[0]=='\0'){
    //blah
}

[ahmedhamdy]

first your code is not readable (this problem you must learn to make your code readable by using spaces and tabs in your code)

[ahmedhamdy]

you can check if array is empty or not

using:

strlen(friend1[contact_checker].name1)==0;

or

strcmp(friend1[contact_checker].name1,"")==0;

or 

 friend1[0].name1=='\0';

[ahmedhamdy]

your code will be that after using one condition from three condition:

#include<stdio.h>
#include<conio.h>
#include<string.h>


typedef struct{
char name1[15];
char name2[15];
char ph_number[15];
char email[25];
}contact;

contact friend1[3];

int menu(void);
void contact_check(int);


int main()
{

     int select1,a=0;
     clrscr();

      select1=menu();

     switch (select1)
     {

       case 1:
        {
             do{
                  printf ("First name\n");
                  scanf  ("%s", friend1[a].name1);

                  printf ("\nLast name\n");
                  scanf  ("%s", friend1[a].name2);

                  printf ("\nPhone number\n");
                  scanf  ("%s", friend1[a].ph_number);

                  printf ("\nE-mail\n");
                  scanf  ("%s", friend1[a].email);

                  a++;
                  select1=menu();

                }while (select1!=2);

                 break;
         }
      case 2:

                contact_check(a);
                 break;
    }

         contact_check(a);

getch();
return 0;
}

int menu()
{
    int select1;

    printf("\t\t\tPhonebook\n");
    printf("\t\t\t=========\n");
    printf("1:New contact\n2:Contact list\n");
    scanf ("%d",&select1);

    return select1;
}

void contact_check(int a)
{
  int contact_checker=0,contact_print;

   if(strlen(friend1[contact_checker].name1)==0&&strlen(friend1[contact_checker].name2)==0     &&strlen(friend1[contact_checker].ph_number)==0&&strlen(friend1[contact_checker].email)==0)
   {
     printf ("No contacts in your phonebook");
   } 
  else
   {
      for (contact_print=0;contact_print<a;contact_print++)
         {   
           printf ("\n%s %s\n", friend1[contact_print].name1,friend1[contact_print].name2);
           printf ("%s\n", friend1[contact_print].ph_number);
           printf ("%s\n", friend1[contact_print].email);
         }
   }


}   

[ahmedhamdy]

i had remove all global variables and put them into main function and functions

[ahmedhamdy]

i had change main function in your code

#include<stdio.h>
#include<conio.h>
#include<string.h>


typedef struct{
char name1[15];
char name2[15];
char ph_number[15];
char email[25];
}contact;

//int select2;
contact friend1[3];

int menu(void);
void contact_check(int);


int main()
{

     int select,a=0;
     clrscr();

     do
     {
        select=menu();

         switch(select)
         {
            case 1:
             {
                  printf ("First name\n");
                  scanf  ("%s", friend1[a].name1);

                  printf ("\nLast name\n");
                  scanf  ("%s", friend1[a].name2);

                  printf ("\nPhone number\n");
                  scanf  ("%s", friend1[a].ph_number);

                  printf ("\nE-mail\n");
                  scanf  ("%s", friend1[a].email);

                  a++;
                  break;      
             }
             case 2:
             {
                 contact_check(a);
                 break;  
             }
         }

     }while(select!=3)


getch();
return 0;
}

int menu()
{
    int select1;

    printf("\t\t\tPhonebook\n");
    printf("\t\t\t=========\n");
    printf("1:New contact\n2:Contact list\n3:Exit\n");
    scanf ("%d",&select1);

    return select1;
}

void contact_check(int a)
{
  int contact_checker=0,contact_print;


   if(strlen(friend1[contact_checker].name1)==0&&strlen(friend1[contact_checker].name2)==0
   &&strlen(friend1[contact_checker].ph_number)==0&&strlen(friend1[contact_checker].email)==0)
   {
     printf ("No contacts in your phonebook");
   } 
  else
   {
      for (contact_print=0;contact_print<a;contact_print++)
         {   
           printf ("\n%s %s\n", friend1[contact_print].name1,friend1[contact_print].name2);
           printf ("%s\n", friend1[contact_print].ph_number);
           printf ("%s\n", friend1[contact_print].email);
         }
   }


}