Problems printing out a string

Question

This is my code:

typedef struct person
{
    char firstName[40];
    char lastName[40];
    char id[40];
} Person;

struct personDataBase
{
    Person personList[100];
    int numOfPersons;
} personDataBase;

Person createPerson()
{
    Person p;
    printf("Please enter your first name:\n");
    gets(p.firstName);
    printf("Please enter your last name:\n");
    gets(p.lastName);
    printf("Please enter your ID number:\n");
    gets(p.id);
    for (int i = 0; i < 100; i++)
    {
        while (strcmp(p.id, personDataBase.personList[i].id) == 0)
        {
            printf("ID already registered in the system, please enter ID correctly:\n");
            gets(p.id);
        }
    }
    return p;
    printf("** Client registered successfully **\n");
}

void addPerson()
{
    personDataBase.personList[personDataBase.numOfPersons] = createPerson();
    personDataBase.numOfPersons++;
    printf("** New person added to the system **\n");
}

int main()
{
    addPerson();
    puts(personDataBase.personList[personDataBase.numOfPersons].firstName);
    puts(personDataBase.personList[personDataBase.numOfPersons].lastName);
    puts(personDataBase.personList[personDataBase.numOfPersons].id);
    return 0;
}

When I try to print the person's details and it just prints out BLANK code.

Output:

Please enter your first name:
John 
Please enter your last name:
Smith
Please enter your ID number:
12312314
** New person added to the system **


//End of the code (the prompt) -- >

I don't know why it prints out blank instead of the person's values

I tried to type : puts(personDataBase.personList[0].id);

instead and it is working, but I want to use the code in the main.

Array indices in c are 0..n-1 (where n is the size of the array), so `personDataBase.personList[personDataBase.numOfPersons]` is accessing an element out of the array. — wohlstad, Sep 14 '22 at 16:55
Please don’t shout in all caps and please use a title which actually explains your question, not a plea for help. — user438383, Sep 14 '22 at 16:57
Please read [ask] on how to select an appropriate title for your question. — Andreas Wenzel, Sep 14 '22 at 16:59
Code is easier to read and to copy/paste and compile if you *don't* break it into sections with "helpful" narration. — Weather Vane, Sep 14 '22 at 17:01
Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. — Community, Sep 14 '22 at 18:55

Vlad from Moscow · Answer 1 · 2022-09-14T17:13:04.263

The function addPerson

void addPerson()
{
    personDataBase.personList[personDataBase.numOfPersons] = createPerson();
    personDataBase.numOfPersons++;
    printf("** New person added to the system **\n");
}

increases the data member numOfPersons:

personDataBase.numOfPersons++;

So to output the last added person you need to use the expression personDataBase.numOfPersons - 1 as an index.

That is in main you can write for example

int main( void )
{
    addPerson();
    
    for ( int i = 0; i < personDataBase.numOfPersons; i++ )
    {
        puts(personDataBase.personList[i].firstName);
        puts(personDataBase.personList[i].lastName);
        puts(personDataBase.personList[i].id);
    }

    return 0;
}

Pay attention to that the function gets is unsafe and is not supported by the C Standard. Instead use the function fgets.

Also it is not a good idea to use file scope variables and when functions depend on file scope variables. You should avoid such a design.

Thank you very much for your answer I feel ashamed that I didn't see it earlier haha. by the way - I am not working with files right now I am just doing a project using structs, so I dont use fgets — דניאל בוזגלו, Sep 15 '22 at 09:02

Problems printing out a string

1 Answers1