1. Network Programming CSC- 341
Instructor:
Junaid Tariq,
Lecturer,
Department of Computer Science

2. 13
Lecture
Network Programming

3. 3.9 readn, writen, and realine Functions
#include “unp.h”
ssize_t readn(int filedes, void *buff, size_t nbytes);
ssize_t writen(int filedes, const void *buff, size_t nbytes);
ssize_t readline(int filedes, void *buff, size_t maxline);
All return: number of bytes read or written, -1 on error

4. Readn()

5. writen

6. readline

7. 3.10 Isfdtype function
Test a Descriptor to see if it is of a specified type
historically : fstat function used
==> testing the returned value st_mode value using one of the S_IFxxx macro.
#include <sys/stat.h>
int isfdtype(int fd, int fdtype);
/* return:1 if descriptor of specified type, 0 if not,
-1 on error */
/* To test for a socket, fdtype is S_IFSOCK.*/

8. #ifndef S_IFSOCK
#error S_IFSOCK not defined
#endif
int isfdtype(int fd, int fdtype) {
struct stat buf;
if(fstat (fd, &buf) < 0)
return (-1);
if((buf.st_mode & S_IFMT) == fdtype)
return (1);
else
return (0); }

9. st_mode field The following flags are defined for the st_mode field:
S_IFMT bit mask for the file type bit fields
S_IFSOCK socket
S_IFLNK symbolic link
S_IFREG regular file
S_IFBLK block device
S_IFDIR directory
S_IFCHR character device
S_IFIFO FIFO