Specifications

CAVR-4

File input and output

AVR® IAR C/C++ Compiler

Reference Guide

CUSTOMIZING FORMATTING CAPABILITIES

To customize the formatting capabilities, you need to set up a library project, see

Building and using a customized library, page 62. Define the configuration symbols

according to your application requirements.

File input and output

The library contains a large number of powerful functions for file I/O operations. If you

use any of these functions you need to customize them to suit your hardware. In order

to simplify adaptation to specific hardware, all I/O functions call a small set of primitive

functions, each designed to accomplish one particular task; for example, __

open opens

a file, and __

write outputs a number of characters.

Note that file I/O capability in the library is only supported by libraries with full library

configuration, see Library configurations, page 55. In other words, file I/O is supported

when the configuration symbol

__DLIB_FILE_DESCRIPTOR is enabled. If not enabled,

functions taking a FILE * argument cannot be used.

Template code for the following I/O files are included in the product:

The primitive functions identify I/O streams, such as an open file, with a file descriptor

that is a unique integer. The I/O streams normally associated with stdin, stdout, and

stderr have the file descriptors 0, 1, and 2, respectively.

Note: If you link your library with I/O debugging support, C-SPY variants of the

low-level I/O functions will be linked for interaction with C-SPY. For more

information, see Debug support in the runtime library, page 56.

I/O function File Description

__close close.c Closes a file.

__lseek lseek.c Sets the file position indicator.

__open open.c Opens a file.

__read read.c Reads a character buffer.

__write write.c Writes a character buffer.

remove remove.c Removes a file.

rename rename.c Renames a file.

Table 21: Low-level I/O files