Why am i getting garbage in for loop using string array, gets and puts?

Question

The puts function doesn't print the 3 strings as i input them. They contain garbage.

#include <stdio.h>
#include <stdlib.h>

int main ()
{
    char para[20][3];
    int x;

    for(x=0; x<3; x++)
    {
      gets(para[x]);
      fflush(stdin);        
    }

    for(x=0; x<3; x++)
      puts(para[x]);

    return 0;
}

1. `gets` doesn't exist anymore (since C11). 2. Assuming you have an ancient implementation where `gets` is available, you can't anymore than 2 chars because there's no space per call (that's the reason you should *never* use `gets`!). — P.P, Feb 28 '18 at 15:01
What you need to do, is to take your source of learning (teacher or book) and then burn it with fire. Then get a better one. — Lundin, Feb 28 '18 at 15:08
@Adder, yes, but a 2D array contains the same number of chars right? so it shouldn't be an issue. True, the strings could be truncated, but garbage? no. — Jean-François Fabre, Feb 28 '18 at 15:12
@Jean, input longer than 3 characters will overflow into the other strings. Moreover the strings would not contain a terminating zero at position 3 — Adder, Feb 28 '18 at 15:18
See [Why `gets()` is so dangerous it should **never** be used!](https://stackoverflow.com/questions/1694036/why-is-the-gets-function-dangerous-why-should-it-not-be-used) — Jonathan Leffler, Feb 28 '18 at 15:19
See also [Using `fflush(stdin)`](https://stackoverflow.com/questions/2979209/) — Jonathan Leffler, Feb 28 '18 at 15:21
@Jean-FrançoisFabre, Yes, it was mixed strings not garbage. — PapoShow, Feb 28 '18 at 15:48

score 2 · Answer 1 · answered Feb 28 '18 at 15:01

fflush(stdin);

is undefined behavior. It should be one output or update stream which is passed to fflush. This, what you have done might result in something weird to normal behavior.

gets is deprecated and not meant to be used. Use fgets instead. You should be able to enter 2 characters and a \n with the array size shown. Maybe you meant para[3][20]. gets has no safety over buffer overflow. That is there is fgets in the form of specifying the number of characters you want to read.

Why am i getting garbage in for loop using string array, gets and puts?

1 Answers1