GNU Info

(libc.info)I/O Concepts

---

Next: File Names Up: I/O Overview

---

Enter node , (file) or (file)node

Input/Output Concepts
=====================

   Before you can read or write the contents of a file, you must
establish a connection or communications channel to the file.  This
process is called "opening" the file.  You can open a file for reading,
writing, or both.

   The connection to an open file is represented either as a stream or
as a file descriptor.  You pass this as an argument to the functions
that do the actual read or write operations, to tell them which file to
operate on.  Certain functions expect streams, and others are designed
to operate on file descriptors.

   When you have finished reading to or writing from the file, you can
terminate the connection by "closing" the file.  Once you have closed a
stream or file descriptor, you cannot do any more input or output
operations on it.

Streams and File Descriptors

The GNU Library provides two ways

to access the contents of files.

File Position

The number of bytes from the

beginning of the file.