Cannot input from "gets()"

Question

I wrote a c program that prompts the user enter their account information into the system and then print them out. I tried to use "gets()" to capture strings. However, it skipped the question for user's address and jumped into the question for state and city. I believed the problem is the "gets()"function. Could someone please help me with it?

#include <stdio.h>
#include <stdlib.h>
#define MAXLEN 40
struct account
{
    long unsigned number;
    char address[MAXLEN];
    char cityState[MAXLEN];
    int zip;
    double balances;
    double credit;
    char name[MAXLEN];
};

int main(void)
{
    struct account memebr;
    puts("Please enter the account number");
    scanf("%lu", &memebr.number);
    puts("Please enter the street address");
    while(getchar() != '\n')
        gets(memebr.address);
    puts("Please enter your city/state");
    while(getchar() != '\n')
        gets(memebr.cityState);
    puts("Please enter your zip code");
    scanf("%d", &memebr.zip);
    puts("Please enter your balances");
    scanf("%lf", &memebr.balances);
    puts("Please enter your credit limit");
    scanf("%lf", &memebr.credit);
    puts("Please enter your name");
    while(getchar() != '\n')
        gets(memebr.name);

    printf("Account number: %lu\n", memebr.number);
    printf("The street address is : %s\n", memebr.address);
    printf("The owner comes from: %s\n", memebr.cityState);
    printf("The zip code is: %d\n", memebr.zip);
    printf("The owner's balances: %.2f\n", memebr.balances);
    printf("The owner's credit limit: %.2f\n", memebr.credit);
    printf("The owener is: %s\n", memebr.name);
    return 0;

}

Why are you using `gets()`. It's no longer a standard function, and it's dangerous. — Iharob Al Asimi, May 17 '16 at 01:02
`while(getchar() != '\n') gets(memebr.address);` --> `while(getchar() != '\n'); gets(memebr.address);`, `while(getchar() != '\n') gets(memebr.cityState);` --> `gets(memebr.cityState);`, `while(getchar() != '\n') gets(memebr.name);` --> `while(getchar() != '\n'); gets(memebr.name);` Also `gets` has been abolished. — BLUEPIXY, May 17 '16 at 01:10
What do you think code like this does: `while(getchar() != '\n') gets(memebr.name);`? — David Schwartz, May 17 '16 at 05:05
the function: `gets()` has been depreciated for years and in the latest c standard it is completely removed. Your compiler should have told you that. The best replacement is the function: `fgets()` (which does have a different set of parameters from`gets()` Suggest read the man page for `fgets()` so you will know what to expect and how to modify your code. — user3629249, May 18 '16 at 03:45

score 1 · Answer 1 · answered May 17 '16 at 01:04

You are asking for input twice, and getchar() will only return when the buffer is flushed, i.e when Enter¹ is pressed. Thus, the getchar() call consumes everything and then you will have to type the same again for gets() to take it.

Try like this

fgets(member.name, sizeof(member.name), stdin);

instead of

while (getchar() != '\n')
    gets(member.name);

Notice that I replaced gets() with fgets() which is safer and is still part of the c standard.

¹_{Actually, when '\n' is inserted into the buffer.}

score 0 · Answer 2 · edited May 23 '17 at 11:59

Referring to the previous question "getchar does not stop when using scanf", the input is only sent to the program after you typed a newline, but scanf("%s", command );leaves the newline in the input buffer. And then the following getchar() would return the newline immediately. That's why the program does not wait for the further input.

As a result, you need to make sure to clean your std input buffer before reading follow-up input. Modify your code:

scanf("%lu", &memebr.number);
puts("Please enter the street address");
while(getchar() != '\n')
    gets(memebr.address);

to

scanf("%lu", &memebr.number);                                                         
do {
  c = getchar();
}while(c != '\n' && c != EOF);
puts("Please enter the street address");
gets(memebr.address);

should be ok to execute the program.

Cannot input from "gets()"

2 Answers2