sample.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <sys/uio.h>
#include <unistd.h>

int main()
{
  struct iovec iov[3];
  ssize_t nr;
  int fd, i;

  char *buf[] = {
    "hello world.\n",
    "alice in wonderland.\n"
    "twitter.\n"
  };

  fd = open("sample_writev.txt", O_WRONLY | O_CREAT | O_TRUNC);
  if (fd == -1) {
    perror("open");
    return 1;
  }

  for (i = 0; i < 3; i++) {
    iov[i].iov_base = buf[i];
    iov[i].iov_len = strlen(buf[i]);
  }

  nr = writev(fd, iov, 3);
  if (nr == -1) {
    perror("writev");
    return 1;
  }
  printf("wrote %zd bytes\n", nr);

  if (close(fd)) {
    perror("close");
    return 1;
  }

  return 0;
}