yes.c mucking about

yes.c

/* See https://www.reddit.com/r/unix/comments/6gxduc/how_is_gnu_yes_so_fast/ for what this is all about, all credit to the original authors. */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

int main() {
    char yes[2]  = "y\n";
    int pagesize = getpagesize() * 8;
    char *buff   = malloc(pagesize);
    int buffused = 0;

    while(buffused < pagesize) {
        memcpy(buff+buffused, yes, 2);
        buffused += 2;
    }

    /* Very minor improvement by setting buffering off */
    setvbuf(stdout, NULL, _IONBF, 0);
    while(fwrite(buff, pagesize, 1, stdout));

    return 1;
}