.\"	$OpenBSD: tcsendbreak.3,v 1.2 1996/08/19 08:34:41 tholo Exp $
.\"
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.Dd "March 4, 1992"
.Dt TCSENDBREAK 3
.Os
.Sh NAME
.Nm tcsendbreak ,
.Nm tcdrain ,
.Nm tcflush ,
.Nm tcflow
.Nd line control functions
.Sh SYNOPSIS
.Fd #include <termios.h>
.Ft int
.Fn tcdrain "int fd"
.Ft int
.Fn tcflow "int fd" "int action"
.Ft int
.Fn tcflush "int fd" "int action"
.Ft int
.Fn tcsendbreak "int fd" "int len"
.Sh DESCRIPTION
The
.Nm tcdrain
function waits until all output written to the terminal referenced by
.Fa fd
has been transmitted to the terminal.
.Pp
The
.Nm tcflow
function suspends transmission of data to or the reception of data from
the terminal referenced by
.Fa fd
depending on the value of
.Fa action .
The value of
.Fa action
must be one of the following:
.Bl -tag -width "TCIOFF"
.It Fa TCOOFF
Suspend output.
.It Fa TCOON
Restart suspended output.
.It Fa TCIOFF
Transmit a STOP character, which is intended to cause the terminal to stop
transmitting data to the system.
(See the description of IXOFF in the
.Ql Input Modes
section of
.Xr termios 4 ).
.It Fa TCION
Transmit a START character, which is intended to cause the terminal to start
transmitting data to the system.
(See the description of IXOFF in the
.Ql Input Modes
section of
.Xr termios 4 ).
.El
.Pp
The
.Nm tcflush
function discards any data written to the terminal referenced by
.Fa fd
which has not been transmitted to the terminal, or any data received
from the terminal but not yet read, depending on the value of
.Fa action .
The value of
.Fa action
must be one of the following:
.Bl -tag -width "TCIOFLUSH"
.It Fa TCIFLUSH
Flush data received but not read.
.It Fa TCOFLUSH
Flush data written but not transmitted.
.It Fa TCIOFLUSH
Flush both data received but not read and data written but not transmitted.
.El
.Pp
The
.Nm tcsendbreak
function transmits a continuous stream of zero-valued bits for four-tenths
of a second to the terminal referenced by
.Fa fd .
The
.Fa len
parameter is ignored in this implementation.
.Sh RETURN VALUES
Upon successful completion, all of these functions return a value of zero.
.Sh ERRORS
If any error occurs, a value of -1 is returned and the global variable
.Va errno
is set to indicate the error, as follows:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument is not a valid file descriptor.
.It Bq Er EINVAL
The
.Fa action
argument is not a proper value.
.It Bq Er ENOTTY
The file associated with
.Fa fd
is not a terminal.
.It Bq Er EINTR
A signal interrupted the
.Nm tcdrain
function.
.El
.Sh SEE ALSO
.Xr tcsetattr 3 ,
.Xr termios 4
.Sh STANDARDS
The
.Nm tcsendbreak ,
.Nm tcdrain ,
.Nm tcflush
and
.Nm tcflow
functions are expected to be compliant with the
.St -p1003.1-88
specification.