TCFLOW(S) UNIX System V TCFLOW(S)
Name
tcdrain, tcflow, tcflush, tcsendbreak - line control
functions
Syntax
#include <termios.h>
int tcdrain (fildes)
int fildes;
int tcflow (fildes, action)
int fildes;
int action;
int tcflush (fildes, queue_selector)
int fildes;
int queue_selector;
int tcsendbreak (fildes, duration)
int fildes;
int duration;
Description
If the terminal is using asynchronous serial data
transmission, the tcsendbreak() function causes transmission
of a continuous stream of zero-valued bits for a specific
duration. If duration is zero, tcsnedbreak transmits zero-
valued bits for at least .25 seconds and not more than .5
seconds. If duration is not set to zero, tcsendbreak sends
zero-valued bits for the amount of time specified by the
implementation.
If the terminal is not using asynchronous serial data
transmission, it is implementation defined whether the
tcsendbreak function sends data to generate a break
condition (as defined by the implementation) or returns
without taking any action.
The tcdrain() function waits until all output written to
fildes has been transmitted.
The tcflush() function discards all data written to fildes
but not transmitted, or data received but not read,
depending on the value of queue_selector:
1. If queue_selector is TCIFLUSH, it flushes data received
but not read.
2. If queue_selector is TCOFLUSH, it flushes data written
but not transmitted.
3. If queue_selector is TCIOFLUSH, it performs both
actions.
The tcflow() function suspends transmission or reception of
dataon the object referred to by fildes, depending onthe
value of action. Possible values for action include:
1. If action is TCOOFF, output is suspended.
2. If action is TCOON, output is restarted.
3. If action is TCIOFF, a STOP character is transmitted,
which is intended to cause the terminal to stop
transmitting data to the system.
4. If action is TCION, a START character is transmitted,
which is intended to cause the terminal to start
transmitting data to the system.
The symbolic constants for the values of queue_selector and
action are defined in <termios.h>. The default on open of a
terminal file is that neither its input nor its output is
suspended.
Return Value
Upon successful completion, these routines return a value of
zero. Otherwise, a value of of -1 is returned and errno is
set to indicate the error. Possible error conditions
include:
tcsendbreak:
[EBADF] The fildes argument is not a valid file descriptor.
[ENOTTY] The file associated with fildes is not a terminal.
tcdrain:
[EBADF] The fildes argument is not a valid file descriptor.
[EINTR] A signal interrupted the function.
[ENOTTY] The file associated with fildes is not a terminal.
tcflush:
[EBADF] The fildes argument is not a valid file descriptor.
[EINVAL] The queue_selector argument is not a proper value.
[ENOTTY] The file associated with fildes is not a terminal.
tcflow:
[EBADF] The fildes argument is not a valid file descriptor.
[EINVAL] The action argument is not a proper value.
[ENOTTY] The file associated with fildes is not a terminal.
See Also
tcattr(S)
Standards Conformance
tcdrain, tcflow, tcflush and tcsendbreak are conformant
with:
AT&T SVID Issue 2, Select Code 307-127.
(printed 6/20/89)