Atmel CAVR-4 Manual De Usuario

CAVR-4

File input and output

Reference Guide

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.

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 

 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.

_ _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.