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Low Level I/O
[C Runtime Library.]

Low level input and output operations. More...

Functions
int	_close (int fd)
	Close a file, device or socket.
long	_filelength (int fd)
	Return the length of a file.
int	_ioctl (int fd, int cmd, void *buffer)
	Perform device specific control functions.
int	_open (CONST char *name, int mode)
	Open a file.
int	_read (int fd, void *buffer, unsigned int count)
	Read data from a file, device or socket.
int	_write (int fd, CONST void *buffer, unsigned int count)
	Write data to a file, device or socket.
int	_write_P (int fd, PGM_P buffer, unsigned int count)
	Writes data from program space to a file, device or socket.

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Detailed Description

Low level input and output operations.

 #include <io.h> 

Standard C runtime file interface to Nut/OS devices.

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Function Documentation

int _close (  int    fd )

Close a file, device or socket. The calling thread may be suspended until all buffered output data has been written. Parameters: fd  Descriptor of a previously opened file, device or connected socket. Returns: 0 if the file was successfully closed or –1 to indicate an error. Examples: playmp3/playmp3.c.

long _filelength (  int    fd )

Return the length of a file. Parameters: fd  Descriptor of a previously opened file, device or connected socket. Returns: Filelength in bytes or -1 in case of an error.

int _ioctl (  int    fd, int    cmd, void *    data )

Perform device specific control functions. Parameters: fd  Descriptor of a previously opened device or connected socket. cmd  Requested control function. data  Points to a buffer that contains any data required for the given control function or receives data from that function. Examples: httpd/httpserv.c, inetq/inetq.c, playmp3/playmp3.c, tcps/tcps.c, threads/threads.c, timers/timers.c, and uart/uart.c.

int _open (  CONST char *    name, int    mode )

Open a file. Parameters: name  The name of a registered device, optionally followed by a colon and a filename. mode  Operation mode. May be any of the following: _O_APPEND Always write at the end. _O_BINARY Raw mode. _O_CREAT Create file if it does not exist. _O_EXCL Open only if it does not exist. _O_RDONLY Read only. _O_RDWR Read and write. _O_TEXT End of line translation. _O_TRUNC Truncate file if it exists. _O_WRONLY Write only. Returns: File descriptor for the opened file or -1 to indicate an error. Examples: playmp3/playmp3.c.

int _read (  int    fd, void *    buffer, unsigned int    count )

Read data from a file, device or socket. Parameters: fd  Descriptor of a previously opened file, device or connected socket. buffer  Pointer to the buffer that receives the data. count  Maximum number of bytes to read. Returns: The number of bytes read, which may be less than the number of bytes specified. A return value of -1 indicates an error. Examples: playmp3/playmp3.c, and uart/uart.c.

int _write (  int    fd, CONST void *    data, unsigned int    count )

Write data to a file, device or socket. Parameters: fd  Descriptor of a previously opened file, device or connected socket. data  Pointer to data in program space to be written. count  Number of bytes to write. Returns: The number of bytes written, which may be less than the number of bytes specified. A return value of -1 indicates an error. Examples: uart/uart.c.

int _write_P (  int    fd, PGM_P    data, unsigned int    count )

Writes data from program space to a file, device or socket. Similar to _write() except that the data is located in program memory. Parameters: fd  Descriptor of a previously opened file, device or connected socket. data  Pointer to data in program space to be written. count  Number of bytes to write. Returns: The number of bytes written, which may be less than the number of bytes specified. A return value of -1 indicates an error. Examples: uart/uart.c.

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