#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
int main(int argc, char **argv) {
    char buf[65536]; long n = 0;
    memset(buf, 0x41, sizeof(buf));
    int fd = open(argv[1], O_RDWR | O_APPEND);
    if (fd < 0) { perror("open"); return 1; }
    for (;;) {
        if (write(fd, buf, sizeof(buf)) != sizeof(buf)) { perror("write"); return 1; }
        n += sizeof(buf);
        if (n >= 2LL*1024*1024*1024) { ftruncate(fd, 0); lseek(fd, 0, SEEK_END); n = 0; }
    }
}