#include <sys/types.h>#include <errno.h>//code from UNIX Network Programming by W.Richard Stevensssize_t readn(int fd, void *vptr, size_t n){	ssize_t nleft, nread;	char *ptr;	ptr = vptr;	nleft = n;	while(nleft > 0){		if( (nread = read(fd, ptr, nleft)) < 0 ){			if(errno == EINTR) nread = 0;			else return -1;		} else if(nread == 0)			break;		//EOF		nleft -= nread;		ptr += nread;	}	return (n - nleft);}ssize_t writen(int fd, void *vptr, size_t n){	size_t nleft, nwritten;	char *ptr;	ptr = vptr;	nleft = n;	while(nleft > 0){		if( (nwritten = write(fd, ptr, nleft)) <=0 ){			if(errno == EINTR) nwritten = 0;			else return -1;		//error		}		nleft -= nwritten;		ptr += nwritten;	}	return n;}ssize_t readline(int fd, void *vptr, size_t maxlen){	ssize_t n, rc;	char c, *ptr;	ptr = vptr;	for(n = 1; n < maxlen; n++){		again:		if( (rc = read(fd, &c, 1)) == 1){			*ptr++ = c;			if(c == '\n') break;	//readover		} else if(rc == 0){			if(n == 1) return 0;	//EOF no data read			else break;		//EOF some data read		} else {			if(errno == EINTR) goto again;			return -1;		//error		}	}	*ptr = 0;	return n;}