TCDRAIN(3P)TCDRAIN(3P)NAME
tcdrain, tcflow, tcflush, tcsendbreak - line control functions
SYNOPSIS
#include <termios.h>
int tcdrain(int fildes);
int tcflow(int fildes, int action);
int tcflush(int fildes, int queue_selector);
int tcsendbreak(int fildes, int duration);
DESCRIPTION
The tcdrain function waits until all output written to the device
referred to by fildes has been transmitted.
The tcflow function controls the flow of output, and attempts to
control the flow of input, for the device referred to by fildes. The
possible values of the action argument are the following constants
defined in <termios.h>:
Constant Description
TCOOFF Suspend output from the device.
TCOON Restart suspended output from the device.
TCIOFF Transmit a STOP character, with the intention of stopping
the terminal from sending any data.
TCION Transmit a START character, with the intention of telling
the terminal to restart the transmission of data.
The tcflush function discards any data written to the device referred
by fildes but not transmitted, or data received, but not read,
depending on the value of queue_selector. The possible values of the
queue_selector are the following constants defined in <termios.h>:
Constant Description
TCIFLUSH Flush all data received but not yet read (input queue).
TCOFLUSH Flush all data written but not yet transmitted (output
queue).
TCIOFLUSH Flush both the input and output queues.
The tcsendbreak causes the transmission of a break condition - a
continuous stream of zero-valued bits. This occurs only if the file
descriptor fildes is associated with a asynchronous communications
line. The transmission lasts for 400 milliseconds.
RETURN VALUE
Upon successful completion, a value of zero is returned. Otherwise a
value of -1 is returned and errno is set to indicate the error.
ERRORS
If any of the following conditions occur, tcdrain, tcflow, tcflush and
tcsendbreak return -1 and sets errno to the corresponding value:
[EBADF] The fildes argument is not a valid file descriptor.
[ENOTTY] The file associated with fildes is not a terminal.
The following error condition may apply to tcdrain:
[EINTR] A signal interrupted the function.
The following error condition may apply to tcflow:
[EINVAL] The action argument is not a proper value.
The following error condition may apply to tcflush:
[EINVAL] The queue_selector argument is not a proper value.
SEE ALSOtermios(4P)4th Berkeley Distribution August 1, 1992 TCDRAIN(3P)
