unpipc.h 를 include 하고 사용한다.
일반 read()&write() 함수와 사용법은 같다.
readn
ssize_t readn(int fd, void *vptr, size_t n)
{
size_t nleft;
ssize_t nread;
char *ptr;
ptr = vptr;
nleft = n;
while (nleft > 0) {
if ( (nread = read(fd, ptr, nleft)) < 0) {
if (errno == EINTR)
nread = 0; /* and call read() again */
else
return(-1);
} else if (nread == 0)
break; /* EOF */
nleft -= nread;
ptr += nread;
}
return(n – nleft); /* return >= 0 */
}
/* end readn */
writen
ssize_t writen(int fd, const void *vptr, size_t n)
/* Taken from UNIX Network Programming – Vol. I by W.R. Stevens */
{
size_t nleft;
ssize_t nwritten;
const char *ptr;
ptr = vptr;
nleft = n;
while(nleft > 0) {
if ( (nwritten = write(fd, ptr, nleft)) <= 0) {
if (errno == EINTR)
nwritten = 0;
else
return (-1);
}
nleft -= nwritten;
ptr += nwritten;
}
return (n);
}