Function fgets doesn't store string

Question

so I want to create an address book program and I have this following code :

#define MAX_VALUE_FOR_ARRAYS 1000

int i = 0 ;
int answer = 0 ;
int number_of_people = 0 ;

FILE* address_book = NULL ;

address_book = fopen("addressBook.txt", "w")  ;

typedef struct People People ;

struct People
{
    char f_name[MAX_VALUE_FOR_ARRAYS]
};

People *persons = NULL ;

printf("A D D R R E S S  B O O K \n\n\n") ;

printf("1. Add a new contact \n") ;
printf("2. View all contacts \n") ;
printf("\nMake your choice : ") ;

while (answer < 1 || answer > 2)
{
    printf("\nWrong input, try again ! : ") ;
    scanf("%d", &answer) ;
}

if (answer == 1)
{
    printf("How many contacts do you want to add ? : ") ;
    scanf("%d", &number_of_people) ;

    persons = malloc(number_of_people * sizeof(People) ) ;

    if (persons == NULL)
    {
        printf("\nMemory allocation failed !") ;
    }

    for (i = 0; i < number_of_people; i++)
    {
        printf("Person %d ", (i+1)) ;
        printf("Enter the first name : ") ;
        fgets(persons[i].f_name, MAX_VALUE_FOR_ARRAYS, stdin) ;

        if (address_book == NULL)
        {
        printf("\nFailed to open file ! ") ;
        }

    fputs(persons[i].f_name, address_book) ;
    fputc('\n', address_book) ;

    }
}

My problem is that the program doesn't want to store the first name ( the "fgets" calling line). It diplays what is in the printf("Enter you first name : ") ; And ignores the following line ( fgets(persons[i].f_name..) , After that it goes directly to the end of the program Help please

The posted code does not compile! How do you expect us to reproduce the problem so we can help you debug it. Please post a [mcve] — user3629249, Jan 09 '19 at 08:53

score 0 · Accepted Answer · answered Jan 06 '19 at 19:48

0

Avoid using both fgets() and scanf() on the same stream.

After scanf("%d", &answer) reads the numeric text and forms an int, the following Enter or '\n' remains in stdin. @xing

Later, fgets(persons[i].f_name,... simple read that remaining '\n' as the input for the first name.

Various solutions:

A) After scanf("%d", &answer); read remaining characters in the line

int ch;
while ((ch = getchar()) != '\n') && ch != EOF) {
  ;
}

B) Use fgets() to read the answer

char buf[50];
fgets(buf, sizeof buf, stdin);
answer = atoi(buf);

C) Use fgets() robustly: int my_get_int(int *i)

if (my_get_int(&answer) == 1) {
  // Success
}

answered Jan 06 '19 at 19:48

chux - Reinstate Monica

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Sir, I've seen your lots of brilliant answers. Could you look at https://stackoverflow.com/questions/54076333/subset-sum-overlapping-dilemma-recursively/54076547 ?? – concurrencyboy Jan 07 '19 at 15:27
@chux I understand better know how both scanf and fgets are working, thanks. I tried all of your solutions and they are all working, but can you explain me more the A and the C ones ? – Jan 07 '19 at 17:49
@TonyStark A) Example: you enter 4 keys `"123\"`, `scanf("%d", &answer);` will consume the `"123"`, leaving the `"\n"` for the next input operation. A following `fgets()` will read the then short remaining line as `"\n"`. If in between, code does A), then all the characters after the `"123"` up to and including the `"\n"` are read - and discarded. Then the following `fgets()` will no get the "\n"`, but read in the next line of input (the first name). – chux - Reinstate Monica Jan 07 '19 at 17:57
@TonyStark C) Refer to the [linked answer](https://stackoverflow.com/a/52846908/2410359) and comment there about any details needed there. – chux - Reinstate Monica Jan 07 '19 at 17:58

Function fgets doesn't store string

1 Answers1