Advanced UNIX Programming

Reading and Writing

The UNIX kernel readies a file for I/O by giving you a file descriptor, which is returned by open(2) or creat(2). The file descriptor might represent an I/O device, a socket or, most often, a regular file. The I/O semantics vary somewhat, depending on what it is that your program is interacting with. This will be noted in a few places as you are introduced to the system calls for I/O.

Introducing read(2) and write(2)

These are perhaps the most basic of all UNIX I/O system calls. Their function synopsis is as follows:

#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>

ssize_t read(int fd,void *buf,size_t nbytes);

ssize_t write(int fd,const void *buf,size_t nbytes);

The read(2) and write(2) calls take the same ...