Datasheet
The C and C++ Libraries
ARM DUI 0067D Copyright © 1999-2001 ARM Limited. All rights reserved. 4-81
4.10.6 _sys_write()
Writes the contents of a buffer to a file previously opened with
_sys_open()
.
Syntax
int _sys_write(FILEHANDLE fh, const unsigned char *buf, unsigned len, int mode)
Implementation
The
mode
parameter isa bitmap describing the state of the file connected to
fh
, whether
it is a binary file, and how it is buffered. The mode bits might be important if the file is
connected to a terminal device because they specify whether or not the device is to be
used raw (for example, whether the terminal input must be echoed). See the
_IOxxx
constants in
stdio.h
for definitions of user-accessible mode bits.
The default semihosting implementation of
_sys_write()
does not pass the
mode
parameter, because it is not required by the
SYS_WRITE (0x05)
semihosting SWI. If you
are retargeting the C library, and you require the
mode
parameter, you must reimplement
sys_io.o
.
Returns
The return value is either:
• a positive number representing the number of characters not written (so any
nonzero return value denotes a failure of some sort)
• a negative number indicating an error.