writen and readn

#include <unistd.h>

ssize_t writen(int fd, const void *vptr, size_t n)

{

  const char *ptr = vptr;

  size_t nleft = n;

  ssize_t nwriten;

  while (nleft > 0) {

if ( (nwriten = write(fd, ptr, nleft)) <= 0)

  return (nwriten);

nleft -= nwriten;

ptr += nwriten;

  }

  return(n);

}

ssize_t readn(int fd, const void *vptr, size_t n)

{

  const char *ptr = vptr;

  size_t nleft = n;

  ssize_t nread;

  while (nleft > 0) {

if ( (nread = read(fd, ptr, nleft)) <= 0)

  return (nread);

nleft -= nread;

ptr += nread;

  }

  return(n - nleft);

}