scanf or getchar 10000 times at a time then program stopped in c

#include "stdio.h"

int main() {
    int ch,i;
     for (i = 0; i < 10000; ++i) {
        scanf(" %c", &ch);
        putchar(ch);
     }
     return 0;
}

It's working if you put chars less than 1000 but if you put chars 10000 at a time then program is stopped. I may think it's because of stdin buffer. How can I solve this?

Here is more specific source.

#include "stdio.h"
#include "stdlib.h"

int main() {
    int i,n;
    char *p, ch;

    scanf("%d", &n);
    p = (char*) malloc(sizeof(char) *n);

    if (p == NULL) {
        return -1;
    }

    for (i = 0; i < n; ++i) {
        scanf(" %c", &ch);
        putchar(ch);
    }
    return 0;
}

Abode source is sample. - put n (word count to read) then put long long strings. program is stopped or wait something to be done.

input example 1.

2000 lsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdkalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalssdafsdfsdfdd

this one is not working.

but below on is working. 2.

1000 jsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdkalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalssdafsdfsdfddkdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalsdklsakdjldjsalkfjalssdafsdfsdfdd1

Solution

Your for loop may have been like the following:

for (i = 0; i < n; ++i) {
    scanf(" %c", &p[i]);
    putchar(p[i]);
}

you can also try to flush your stdin input buffer in your code as adding the following line properly:

fflush(stdin);

Edit: Due to undefined behavior possibility on some systems, an alternative and more common approach may be implemented like the following:

int ch;

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

      // ...
}

or you can change stream buffer size properly by calling setvbuf function below:

int setvbuf (FILE* stream, char* buffer, int mode, size_t size);