What is the best way to read a string? - c

Question

So I'm really confused. I have to write a program in C which is basically an address book, thus I have to get multiple strings from the user (name, ID, phone etc.)
In the beginning I tried using scanf() only but it messed up sometimes with the newline character '\n'. After some googling, I ended up using scanf() for getting single chars or ints (where user answers yes or no questions, or chooses an action from a menu) and fgets() to read the fields of the address book. However, I also had to use fflush(stdin) multiple times after using scanf() which is not recommended here as I have seen. This method worked so far as intended.
So what's the optimal way to read a string from the user? Does fflush(stdin) not offer portability? This is an assignment so I have to think for portability too, since I will execute my code on another computer.
Thank you in advance.
EDIT: So here is what I've got so far. Excuse some words that are written in another language (Albanian). I believe you can understand what's going on.
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
void regjistrim();
void kerkim();
void modifikim();
void fshirje();
void rradhitje();
void display();
#define EMRI 50
#define MBIEMRI 50
#define ID 20
#define TEL 20
#define EMAIL 25
typedef struct addressbook
{
char emri[EMRI];
char mbiemri[MBIEMRI];
char id[ID];
char tel[TEL];
char email[EMAIL];
} addressbook;
FILE* Addressbook;
int main(void)
{
char input[2];
int choice;
printf("----------------ADDRESS BOOK----------------");
printf("\n\n\t1 - Regjistrimi i ri\n");
printf("\n\t2 - Kerkim\n");
printf("\n\t3 - Modifikim\n");
printf("\n\t4 - Fshirje\n");
printf("\n\t5 - Rradhitje\n");
printf("\n\t6 - Afishim i address book\n");
printf("\n\t0 - Exit\n");
fgets(input, 2, stdin);
sscanf(input, "%d", &choice);
while (choice < 0 || choice > 6)
{
printf("\nShtypni nje numer nga 0 - 6: \n");
fgets(input, 2, stdin);
sscanf(input, "%d", &choice);
}
switch (choice)
{
case 1:
regjistrim();
break;
case 2:
kerkim();
break;
case 3:
modifikim();
break;
case 4:
fshirje();
break;
case 5:
rradhitje();
break;
case 6:
display();
break;
case 0:
exit(0);
break;
}
return 0;
}
//Regjistron nje qytetar ne addressbook
void regjistrim()
{
char answer;
addressbook entry;
do
{
Addressbook = fopen("Addressbook.txt", "a+");
printf("\nShtypni emrin: ");
fgets(entry.emri, EMRI, stdin);
printf("\nShtypni mbiemrin: ");
fgets(entry.mbiemri, MBIEMRI, stdin);
printf("\nShtypni ID-in: ");
fgets(entry.id, ID, stdin);
printf("\nShtypni nr. telefoni: ");
fgets(entry.tel, TEL, stdin);
printf("\nShtypni email-in: ");
fgets(entry.email, EMAIL, stdin);
fprintf(Addressbook, "Emri: %sMbiemri: %sID: %sNr. telefoni: %sEmail: %s\n", entry.emri, entry.mbiemri, entry.id, entry.tel,entry.email);
fclose(Addressbook);
printf("\nShtypni y/Y neqoftese doni te regjistroni person tjeter: ");
fgets(answer, 1, stdin);
}
while(answer == 'y' || answer == 'Y');
}

Answer 1

With scanf, you can clear the newlines, like that. Also, I have included fgets too.
#include<stdio.h>
int main(void)
{
int i, N = 5;
char buffer[N];
printf("Enter %d characters\n", N+1);
scanf("%5s", buffer); /* MUST check comments below on this page for this! */
/* Clear trailing input */
while(getchar() != '\n')
/* discard */ ;
for(i = 0 ; i < 5 ; ++i)
printf("|%c|\n", buffer[i]);
printf("End with scanf\n\n");
/*****************************************************/
printf("Enter %d characters\n", N+1);
fgets(buffer, 5, stdin);
for(i = 0 ; i < 5 ; ++i)
printf("|%c|\n", buffer[i]);
printf("End with fgets\n\n");
return 0;
}
Also, this code demonstrates the limit you can put to every function for the input.
Source

Answer 2

Well "optimal" is maybe a bit subjective but I found
doing a separate function to read the number makes things
a bit easier and avoid scanf if you don't absolutely need it e.g.
int readNumber(int min, int max)
{
char number[32];
do
{
if ( fgets( number, sizeof(number), stdin ) != NULL )
{
// note that if 'number' is not a number atoi returns 0
int n = atoi(number);
if ( n>= min && n <= max )
{
return n;
}
}
printf( "please enter a valid value between %d and %d\n", min, max );
}
while ( 1 );
return -1; // never reached
}