path: root/usr/src/man/man4i/termio.4i

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.Dd March 13, 2022
.Dt TERMIO 4I
.Os
.Sh NAME
.Nm termio
.Nd general terminal interface
.Sh SYNOPSIS
.In termio.h
.Fn ioctl "int fildes" "int request" "struct termio *arg"
.Fn ioctl "int fildes" "int request" "int arg"
.Pp
.In termios.h
.Fn ioctl "int fildes" "int request" "struct termios *arg"
.Sh DESCRIPTION
This release supports a general interface for asynchronous communications ports
that is hardware-independent.
The user interface to this functionality is using
function calls (the preferred interface) described in
.Xr termios 3C
or
.Fn ioctl
commands described in this section.
This section also discusses the
common features of the terminal subsystem which are relevant with both user
interfaces.
.Pp
When a terminal file is opened, it normally causes the process to wait until a
connection is established.
In practice, user programs seldom open terminal
files; they are opened by the system and become a user's standard input,
output, and error files.
The first terminal file opened by the session leader
that is not already associated with a session becomes the controlling terminal
for that session.
The controlling terminal plays a special role in handling
quit and interrupt signals, as discussed below.
The controlling terminal is
inherited by a child process during a
.Xr fork 2 .
A process can break this
association by changing its session using
.Xr setsid 2 .
.Pp
A terminal associated with one of these files ordinarily operates in
full-duplex mode.
Characters may be typed at any time, even while output is
occurring, and are only lost when the character input buffers of the system
become completely full, which is rare.
For example, the number of characters in
the line discipline buffer may exceed
.Brq Dv MAX_CANON
and
.Dv IMAXBEL
(see below) is not set, or the user may accumulate
.Brq Dv MAX_INPUT
number of input characters that have not yet been read by some program.
When the input
limit is reached, all the characters saved in the buffer up to that point are
thrown away without notice.
.Ss "Session Management (Job Control)"
A control terminal will distinguish one of the process groups in the session
associated with it to be the foreground process group.
All other process
groups in the session are designated as background process groups.
This foreground process group plays a special role in handling signal-generating
input characters, as discussed below.
By default, when a controlling terminal
is allocated, the controlling process's process group is assigned as
foreground process group.
.Pp
Background process groups in the controlling process's session are subject to a
job control line discipline when they attempt to access their controlling
terminal.
Process groups can be sent signals that will cause them to stop,
unless they have made other arrangements.
An exception is made for members of
orphaned process groups.
.Pp
An orphaned process group is one where the process group (see
.Xr getpgid 2 )
has no members with a parent in a different process group but sharing the same
controlling terminal.
When a member of an orphaned process group attempts to
access its controlling terminal, EIO is returned because there would be no way
to restart the process if it were stopped on one of these signals.
.Pp
If a member of a background process group attempts to read its controlling
terminal, its process group will be sent a
.Dv SIGTTIN
signal, which will
normally cause the members of that process group to stop.
If, however, the
process is ignoring or holding
.Dv SIGTTIN ,
or is a member of an orphaned
process group, the read will fail with
.Va errno
set to
.Er EIO ,
and no signal is sent.
.Pp
If a member of a background process group attempts to write its controlling
terminal and the
.Dv TOSTOP
bit is set in the
.Fa c_lflag
field, its process group is sent a
.Dv SIGTTOU
signal, which will normally cause the
members of that process group to stop.
If, however, the process is ignoring or
holding
.Dv SIGTTOU ,
the write will succeed.
If the process is not ignoring
or holding
.Dv SIGTTOU
and is a member of an orphaned process group, the
write will fail with
.Va errno
set to
.Er EIO ,
and no signal will be sent.
.Pp
If
.Dv TOSTOP
is set and a member of a background process group attempts to
.Fn ioctl
its controlling terminal, and that
.Fn ioctl
will modify terminal parameters (for example,
.Dv TCSETA ,
.Dv TCSETAW ,
.Dv TCSETAF ,
or
.Dv TIOCSPGRP ) ,
its process group will be sent a
.Dv SIGTTOU
signal, which will normally cause the members of that process group to stop.
If, however, the process is ignoring or holding
.Dv SIGTTOU ,
the ioctl will succeed.
If the process is not ignoring or holding
.Dv SIGTTOU
and is a member of an orphaned
process group, the write will fail with
.Va errno
set to
.Er EIO ,
and no signal will be sent.
.Ss "Canonical Mode Input Processing"
Normally, terminal input is processed in units of lines.
A line is delimited by
a newline
.Po
.Sy ASCII LF
.Pc
character, an end-of-file
.Po
.Sy ASCII EOT
.Pc
character, or an end-of-line character.
This means that a program attempting to
read will block until an entire line has been typed.
Also, no matter how many
characters are requested in the read call, at most one line will be returned.
It is not necessary, however, to read a whole line at once; any number of
characters may be requested in a read, even one, without losing information.
.Pp
During input, erase, erase2, and kill processing is normally done.
The
.Sy ERASE
and
.Sy ERASE2
character (by default, the character
.Sy DEL
for
.Sy ERASE
and
.Sy Control-h
for
.Sy ERASE2 )
erases the last character typed.
The
.Sy WERASE
character (the character
.Sy Control-w )
erases the
last "word" typed in the current input line (but not any preceding spaces or
tabs).
A
.Dq word
is defined as a sequence of non-blank characters, with tabs counted as blanks.
None of
.Sy ERASE
or
.Sy ERASE2
or
.Sy WERASE
will erase beyond the beginning of the line.
The
.Sy KILL
character (by default,
the character
.Sy NAK )
kills (deletes) the entire input line, and optionally
outputs a newline character.
All these characters operate on a key stroke basis,
independent of any backspacing or tabbing that may have been done.
The
.Sy REPRINT
character (the character
.Sy Control-r )
prints a newline followed by all characters that have not been read.
Reprinting also occurs automatically if
characters that would normally be erased from the screen are fouled by program
output.
The characters are reprinted as if they were being echoed;
consequently, if
.Dv ECHO
is not set, they are not printed.
.Pp
The
.Sy ERASE ,
.Sy ERASE2 ,
and
.Sy KILL
characters may be entered literally by preceding them with the escape character.
In this case, the escape character is not read.
The erase, erase2, and kill characters may be changed.
.Ss "Non-canonical Mode Input Processing"
In non-canonical mode input processing, input characters are not assembled into
lines, and erase and kill processing does not occur.
The
.Sy MIN
and
.Sy TIME
values are used to determine how to process the characters received.
.Pp
.Sy MIN
represents the minimum number of characters that should be received
when the read is satisfied (that is, when the characters are returned to the
user).
.Sy TIME
is a timer of 0\&.10-second granularity that is used to timeout
bursty and short-term data transmissions.
The four possible values for
.Sy MIN
and
.Sy TIME
and their interactions are described below.
.Bl -tag -width "Case A: Min > 0, Time > 0"
.It Sy Case A: MIN > 0, TIME > 0
In this case,
.Sy TIME
serves as an intercharacter timer and is activated
after the first character is received.
Since it is an intercharacter timer, it
is reset after a character is received.
The interaction between
.Sy MIN
and
.Sy TIME
is as follows: as soon as one character is received, the
intercharacter timer is started.
If
.Sy MIN
characters are received before
the intercharacter timer expires (note that the timer is reset upon receipt of
each character), the read is satisfied.
If the timer expires before
.Sy MIN
characters are received, the characters received to that point are returned to
the user.
Note that if
.Sy TIME
expires, at least one character will be
returned because the timer would not have been enabled unless a character was
received.
In this case (MIN > 0, TIME > 0), the read sleeps until the
.Sy MIN
and
.Sy TIME
mechanisms are activated by the receipt of the first character.
If the number of characters read is less than the number of characters
available, the timer is not reactivated and the subsequent read is satisfied
immediately.
.It Sy Case B: MIN > 0, TIME = 0
In this case, since the value of
.Sy TIME
is zero, the timer plays no role
and only
.Sy MIN
is significant.
A pending read is not satisfied until
.Sy MIN
characters are received (the pending read sleeps until
.Sy MIN
characters are received).
A program that uses this case to read record based
terminal
.Sy I/O
may block indefinitely in the read operation.
.It Sy Case C: MIN = 0, TIME > 0
In this case, since
.Sy MIN
0,
.Sy TIME
no longer represents an
intercharacter timer: it now serves as a read timer that is activated as soon
as a
.Xr read  2
is done.
A read is satisfied as soon as a single character is
received or the read timer expires.
Note that, in this case, if the timer
expires, no character is returned.
If the timer does not expire, the only way
the read can be satisfied is if a character is received.
In this case, the
read will not block indefinitely waiting for a character; if no character is
received within
.Sy TIME
*\&.10 seconds after the read is initiated, the read
returns with zero characters.
.It Sy Case D: MIN = 0, TIME = 0
In this case, return is immediate.
The minimum of either the number of
characters requested or the number of characters currently available is
returned without waiting for more characters to be input.
.El
.Ss "Comparing Different Cases of MIN, TIME Interaction"
Some points to note about
.Sy MIN
and
.Sy TIME :
.Bl -bullet -offset 2n
.It
In the following explanations, note that the interactions of
.Sy MIN
and
.Sy TIME
are not symmetric.
For example, when
.Sy MIN
> 0 and
.Sy TIME
= 0,
.Sy TIME
has no effect.
However, in the opposite case, where
.Sy MIN
= 0 and
.Sy TIME
> 0, both
.Sy MIN
and
.Sy TIME
play a role in that
.Sy MIN
is satisfied with the receipt of a single character.
.It
Also note that in case A
.Po
.Sy MIN
> 0,
.Sy TIME
> 0
.Pc ,
.Sy TIME
represents
an intercharacter timer, whereas in case C
.Po
.Sy MIN
= 0,
.Sy TIME
> 0
.Pc ,
.Sy TIME
represents a read timer.
.El
.Pp
These two points highlight the dual purpose of the
.Sy MIN/TIME
feature.
Cases A and B, where
.Sy MIN
> 0, exist to handle burst mode activity (for
example, file transfer programs), where a program would like to process at
least
.Sy MIN
characters at a time.
In case A, the intercharacter timer is
activated by a user as a safety measure; in case B, the timer is turned off.
.Pp
Cases C and D exist to handle single character, timed transfers.
These cases
are readily adaptable to screen-based applications that need to know if a
character is present in the input queue before refreshing the screen.
In case
C, the read is timed, whereas in case D, it is not.
.Pp
Another important note is that
.Sy MIN
is always just a minimum.
It does not
denote a record length.
For example, if a program does a read of 20 bytes,
.Sy MIN
is 10, and 25 characters are present, then 20 characters will be
returned to the user.
.Ss "Writing Characters"
When one or more characters are written, they are transmitted to the terminal
as soon as previously written characters have finished typing.
nputt characters
are echoed as they are typed if echoing has been enabled.
If a process produces
characters more rapidly than they can be typed, it will be suspended when its
output queue exceeds some limit.
When the queue is drained down to some
threshold, the program is resumed.
.Ss "Special Characters"
Certain characters have special functions on input.
These functions and their default character values are summarized as follows:
.Bl -tag -width REPRINT
.It Sy INTR
(Control-c or
.Sy ASCII ETX )
generates a
.Dv SIGINT
signal.
.Dv SIGINT
is sent to all foreground processes associated with the controlling terminal.
Normally, each such process is forced to terminate, but arrangements may be
made either to ignore the signal or to receive a trap to an agreed upon
location.
(See
.Xr signal.h 3HEAD ) .
.It Sy QUIT
(Control-| or
.Sy ASCII FS )
generates a
.Dv SIGQUIT
signal.
Its treatment
is identical to the interrupt signal except that, unless a receiving process
has made other arrangements, it will not only be terminated but a core image
file (called
.Pa core )
will be created in the current working directory.
.It Sy ERASE
(DEL) erases the preceding character.
It does not erase beyond
the start of a line, as delimited by a
.Sy NL ,
.Sy EOF ,
.Sy EOL ,
or
.Sy EOL2
character.
.It Sy ERASE2
(Control-h or
.Sy ASCII BS )
erases the preceding character, with behaviour identical to that of ERASE.
.It Sy WERASE
(Control-w or
.Sy ASCII ETX )
erases the preceding
.Dq word .
It does not erase beyond the start of a line, as delimited by a
.Sy NL ,
.Sy EOF ,
.Sy EOL ,
or
.Sy EOL2
character.
.It Sy KILL
(Control-u or
.Sy ASCII NAK )
deletes the entire line, as delimited by a
.Sy NL ,
.Sy EOF ,
.Sy EOL ,
or
.Sy EOL2
character.
.It Sy REPRINT
(Control-r or
.Sy ASCII DC2 )
reprints all characters, preceded by a newline, that have not been read.
.It Sy EOF
(Control-d or
.Sy ASCII EOT )
may be used to generate an end-of-file from a terminal.
When received, all the characters waiting to be read are immediately
passed to the program, without waiting for a newline, and the
.Sy EOF
is discarded.
Thus, if no characters are waiting (that is, the
.Sy EOF
occurred
at the beginning of a line) zero characters are passed back, which is the
standard end-of-file indication.
Unless escaped, the
.Sy EOF
character is not
echoed.
Because
.Sy EOT
is the default
.Sy EOF
character, this prevents
terminals that respond to
.Sy EOT
from hanging up.
.It Sy NL
.Pq Sy ASCII LF
is the normal line delimiter.
It cannot be changed or escaped.
.It Sy EOL
.Pq Sy ASCII NULL
is an additional line delimiter, like
.Sy NL .
It is not normally used.
.It Sy EOL2
is another additional line delimiter.
.It Sy SWTCH
(Control-z or
.Sy ASCII EM )
Header file symbols related to this special
character are present for compatibility purposes only and the kernel takes no
special action on matching SWTCH (except to discard the character).
.It Sy SUSP
(Control-z or
.Sy ASCII SUB )
generates a
.Dv SIGTSTP
signal.
.Dv SIGTSTP
stops all processes in the foreground process group for that terminal.
.It Sy DSUSP
(Control-y or
.Sy ASCII EM ) .
It generates a
.Dv SIGTSTP
signal as
.Sy SUSP
does, but the signal is sent when a process in the foreground
process group attempts to read the
.Sy DSUSP
character, rather than when it is typed.
.It Sy STOP
(Control-s or
.Sy ASCII DC3 )
can be used to suspend output temporarily.
It is useful with
.Sy CRT
terminals to prevent output from disappearing before it can be read.
While output is suspended,
.Sy STOP
characters are ignored and
not read.
.It Sy START
(Control-q or
.Sy ASCII DC1 )
is used to resume output.
Output has been suspended by a
.Sy STOP
character.
While output is not suspended,
.Sy START
characters are ignored and not read.
.It Sy DISCARD
(Control-o or
.Sy ASCII SI )
causes subsequent output to be discarded.
Output is discarded until another
.Sy DISCARD
character is typed, more input
arrives, or the condition is cleared by a program.
.It Sy STATUS
(Control-t or
.Sy ASCII DC4 )
generates a
.Dv SIGINFO
signal.
Processes with a handler will output status information when they receive
.Dv SIGINFO ,
for
example,
.Xr dd 8 .
If a process does not have a
.Dv SIGINFO
handler, the
signal will be ignored.
.It Sy LNEXT
(Control-v or
.Sy ASCII SYN )
causes the special meaning of the next character to be ignored.
This works for all the special characters mentioned above.
It
allows characters to be input that would otherwise be interpreted by the system
(for example
.Sy KILL ,
.Sy QUIT ) .
The character values for
.Sy INTR ,
.Sy QUIT ,
.Sy ERASE ,
.Sy ERASE2 ,
.Sy WERASE ,
.Sy KILL ,
.Sy REPRINT ,
.Sy EOF ,
.Sy EOL ,
.Sy EOL2 ,
.Sy SWTCH ,
.Sy SUSP ,
.Sy DSUSP ,
.Sy STOP ,
.Sy START ,
.Sy DISCARD ,
.Sy STATUS ,
and
.Sy LNEXT
may be changed to suit individual tastes.
If the value of a special control character
is
.Dv _POSIX_VDISABLE
(0), the function of that special control character is disabled.
The
.Sy ERASE ,
.Sy ERASE2 ,
.Sy KILL ,
and
.Sy EOF
characters may be
escaped by a preceding backslash (\e) character, in which case no special
function is done.
Any of the special characters may be preceded by the
.Sy LNEXT
character, in
which case no special function is done.
.El
.Ss "Modem Disconnect"
When a modem disconnect is detected, a
.Dv SIGHUP
signal is sent to the
terminal's controlling process.
Unless other arrangements have been made, these
signals cause the process to terminate.
If
.Dv SIGHUP
is ignored or caught,
any subsequent read returns with an end-of-file indication until the terminal
is closed.
.Pp
If the controlling process is not in the foreground process group of the
terminal, a
.Dv SIGTSTP
is sent to the terminal's foreground process group.
Unless other arrangements have been made, these signals cause the processes to
stop.
.Pp
Processes in background process groups that attempt to access the controlling
terminal after modem disconnect while the terminal is still allocated to the
session will receive appropriate
.Dv SIGTTOU
and
.Dv SIGTTIN
signals.
Unless other arrangements have been made, this signal causes the processes to
stop.
.Pp
The controlling terminal will remain in this state until it is reinitialized
ithh a successful open by the controlling process, or deallocated by the
controlling process.
.Ss "Terminal Parameters"
The parameters that control the behavior of devices and modules providing the
.Vt termios
interface are specified by the
.Vt termios
structure defined by
.In termios.h .
Several
.Xr ioctl 2
system calls that fetch or change
these parameters use this structure that contains the following members:
.Bd -literal -offset 2n
tcflag_t	c_iflag;	/* input modes */
tcflag_t	c_oflag;	/* output modes */
tcflag_t	c_cflag;	/* control modes */
tcflag_t	c_lflag;	/* local modes */
cc_t		c_cc[NCCS];	/* control chars */
.Ed
.Pp
The special control characters are defined by the array
.Fa c_cc .
The symbolic name
.Dv NCCS
is the size of the Control-character array and is also
defined by
.In termios.h .
The relative positions, subscript names, and
typical default values for each function are as follows:
.Bl -column "Relative Position" "Subscript Name" "Typical Default Value"
.It Relative Position Ta Subscript Name Ta Typical Default Value
.It 0 Ta Dv VINTR Ta Sy ETX
.It 1 Ta Dv VQUIT Ta Sy FS
.It 2 Ta Dv VERASE Ta Sy DEL
.It 3 Ta Dv VKILL Ta Sy NAK
.It 4 Ta Dv VEOF Ta Sy EOT
.It 5 Ta Dv VEOL Ta Sy NUL
.It 6 Ta Dv VEOL2 Ta Sy NUL
.It 7 Ta Dv VWSTCH Ta Sy NUL
.It 8 Ta Dv VSTART Ta Sy NUL
.It 9 Ta Dv VSTOP Ta Sy DC3
.It 10 Ta Dv VSUSP Ta Sy SUB
.It 11 Ta Dv VDSUSP Ta Sy EM
.It 12 Ta Dv VREPRINT Ta Sy DC2
.It 13 Ta Dv VDISCARD Ta Sy SI
.It 14 Ta Dv VWERASE Ta Sy ETB
.It 15 Ta Dv VLNEXT Ta Sy SYN
.It 16 Ta Dv VSTATUS Ta Sy DC4
.It 17 Ta Dv VERASE2 Ta Sy BS
.It 18-19 Ta Reserved Ta
.El
.Ss "Input Modes"
The
.Fa c_iflag
field describes the basic terminal input control:
.Pp
.Bl -tag -width "IMAXBEL" -offset 2n -compact
.It Dv IGNBRK
Ignore break condition.
.It Dv BRKINT
Signal interrupt on break.
.It Dv IGNPAR
Ignore characters with parity errors.
.It Dv PARMRK
Mark parity errors.
.It Dv INPCK
Enable input parity check.
.It Dv ISTRIP
Strip character.
.It Dv INLCR
Map NL to CR on input.
.It Dv IGNCR
Ignore CR.
.It Dv ICRNL
Map CR to NL on input.
.It Dv IUCLC
Map upper-case to lower-case on input.
.It Dv IXON
Enable start/stop output control.
.It Dv IXANY
Enable any character to restart output.
.It Dv IXOFF
Enable start/stop input control.
.It Dv IMAXBEL
Echo
.Sy BEL
on input line too long.
.El
.Pp
If
.Dv IGNBRK
is set, a break condition (a character framing error with data
all zeros) detected on input is ignored, that is, not put on the input queue
and therefore not read by any process.
If
.Dv IGNBRK
is not set and
.Dv BRKINT
is set, the break condition shall flush the input and output
queues and if the terminal is the controlling terminal of a foreground process
group, the break condition generates a single
.Dv SIGINT
signal to that
foreground process group.
If neither
.Dv IGNBRK
nor
.Dv BRKINT
is set, a
break condition is read as a single
.Ql \e0
.Pq Sy ASCII NULL
character, or if
.Dv PARMRK
is set, as
.Ql \e377 ,
.Ql \e0 ,
.Em c ,
where
.Ql \e377
is a single character
with value 377 octal (0xff hex, 255 decimal),
.Ql \e0
is a single character with value
.Sy 0 ,
and
.Em c
is the errored character received.
.Pp
If
.Dv IGNPAR
is set, a byte with framing or parity errors (other than
break) is ignored.
.Pp
If
.Dv PARMRK
is set, and
.Dv IGNPAR
is not set, a byte with a framing or
parity error (other than break) is given to the application as the
three-character sequence:
.Ql \e377 ,
.Ql \e0 ,
c, where
.Ql \e377
is a single character with value 377 octal (0xff hex, 255 decimal),
.Ql \e0
is a single character with value 0, and c is the errored character received.
To avoid ambiguity in this case, if
.Dv ISTRIP
is not set, a valid character
of
.Ql \e377
is given to the application as
.Ql \e377 .
If neither
.Dv IGNPAR
nor
.Dv PARMRK
is set, a framing or parity error (other than break) is given to
the application as a single
.Ql \e0
.Po
.Sy ASCII NULL
.Pc
character.
.Pp
If
.Dv INPCK
is set, input parity checking is enabled.
If
.Dv INPCK
is not
set, input parity checking is disabled.
This allows output parity generation
without input parity errors.
Note that whether input parity checking is
enabled or disabled is independent of whether parity detection is enabled or
disabled.
If parity detection is enabled but input parity checking is
disabled, the hardware to which the terminal is connected will recognize the
parity bit, but the terminal special file will not check whether this is set
correctly or not.
.Pp
If
.Dv ISTRIP
is set, valid input characters are first stripped to seven
bits, otherwise all eight bits are processed.
.Pp
If
.Dv INLCR
is set, a received
.Sy NL
character is translated into a
.Sy CR
character.
If
.Dv IGNCR
is set, a received
.Sy CR
character is ignored (not read).
Otherwise, if
.Dv ICRNL
is set, a received
.Sy CR
character is translated into a
.Sy NL
character.
.Pp
If
.Dv IUCLC
is set, a received upper case, alphabetic character is
translated into the corresponding lower case character.
.Pp
If
.Dv IXON
is set, start/stop output control is enabled.
A received
.Sy STOP
character suspends output and a received
.Sy START
character
restarts output.
The
.Sy STOP
and
.Sy START
characters will not be read,
but will merely perform flow control functions.
If
.Dv IXANY
is set, any
input character restarts output that has been suspended.
.Pp
If
.Dv IXOFF
is set, the system transmits a
.Sy STOP
character when the
input queue is nearly full, and a
.Sy START
character when enough input has
been read so that the input queue is nearly empty again.
.Pp
If
.Dv IMAXBEL
is set, the
.Sy ASCII BEL
character is echoed if the input stream overflows.
Further input is not stored, but any input already present in
the input stream is not disturbed.
If
.Dv IMAXBEL
is not set, no
.Sy BEL
character is echoed, and all input present in the input queue is discarded if
the input stream overflows.
.Ss "Output Modes"
The
.Fa c_oflag
field specifies the system treatment of output:
.Pp
.Bl -tag -width ONLRET -offset 2n -compact
.It Dv OPOST
Post-process output.
.It Dv OLCUC
Map lower case to upper on output.
.It Dv ONLCR
Map NL to CR-NL on output.
.It Dv OCRNL
Map CR to NL on output.
.It Dv ONOCR
No
.Sy CR
output at column 0.
.It Dv ONLRET
.Sy NL
performs
.Sy CR
function.
.It Dv OFILL
Use fill characters for delay.
.It Dv OFDEL
Fill is
.Sy DEL ,
else
.Sy INULL .
.It Dv NLDLY
Select newline delays:
.Bl -tag -width NL0 -compact -offset 2n
.It Sy NL0
.It Sy NL1
.El
.It Dv CRDLY
Select carriage-return delays:
.Bl -tag -width CR0 -compact -offset 2n
.It Dv CR0
.It Dv CR1
.It Dv CR2
.It Dv CR3
.El
.It Dv TABDLY
Select horizontal tab delays or tab expansion:
.Bl -tag -width XTABS -compact -offset 2n
.It Dv TAB0
.It Dv TAB1
.It Dv TAB2
.It Dv TAB3
Expand tabs to spaces
.It Dv XTABS
Expand tabs to spaces
.El
.It Dv BSDLY
Select backspace delays:
.Bl -tag -width BS0 -offset 2n -compact
.It Dv BS0
.It Dv BS1
.El
.It Dv VTDLY
Select vertical tab delays:
.Bl -tag -width VT0 -offset 2n -compact
.It Dv VT0
.It Dv VT1
.El
.It Dv FFDLY
Select form feed delays:
.Bl -tag -width FF0 -offset 2n -compact
.It Dv FF0
.It Dv FF1
.El
.El
.Pp
If
.Dv OPOST
is set, output characters are post-processed as indicated by the
remaining flags; otherwise, characters are transmitted without change.
.Pp
If
.Dv OLCUC
is set, a lower case alphabetic character is transmitted as the
corresponding upper case character.
This function is often used in conjunction
with
.Dv IUCLC .
.Pp
If
.Dv ONLCR
is set, the
.Sy NL
character is transmitted as the
.Sy CR-NL
character pair.
If
.Dv OCRNL
is set, the
.Sy CR
character is transmitted as the
.Sy NL
character.
If
.Dv ONOCR
is set, no
.Sy CR
character is transmitted when at column 0 (first position).
If
.Dv ONRET
is set, the
.Sy NL
character is assumed to do the carriage-return function; the column
pointer is set to 0 and the delays specified for
.Sy CR
are used.
Otherwise, the
.Sy NL
character is assumed to do just the line-feed function; the column
pointer remains unchanged.
The column pointer is also set to 0 if the
.Sy CR
character is actually transmitted.
.Pp
The delay bits specify how long transmission stops to allow for mechanical or
other movement when certain characters are sent to the terminal.
In all cases, a value of 0 indicates no delay.
If
.Dv OFILL
is set, fill characters are transmitted for delay instead of a timed delay.
This is useful for high baud rate terminals that need only a minimal delay.
If
.Dv OFDEL
is set, the
fill character is
.Sy DEL ;
otherwise it is
.Sy NULL .
.Pp
If a form-feed or vertical-tab delay is specified, it lasts for about 2
seconds.
.Pp
Newline delay lasts about 0\&.10 seconds.
If
.Dv ONLRET
is set, the carriage-return delays are used instead of the newline delays.
If
.Dv OFILL
is set, two fill characters are transmitted.
.Pp
Carriage-return delay type 1 is dependent on the current column position, type
2 is about 0\&.10 seconds, and type 3 is about 0\&.15 seconds.
If
.Dv OFILL
is set, delay type 1 transmits two fill characters, and type 2 transmits four
fill characters.
.Pp
Horizontal-tab delay type 1 is dependent on the current column position.
Type 2 is about 0\&.10 seconds.
Type 3 specifies that tabs are to be expanded into spaces.
If
.Dv OFILL
is set, two fill characters are transmitted for any delay.
.Pp
Backspace delay lasts about 0\&.05 seconds.
If
.Dv OFILL
is set, one fill character is transmitted.
.Pp
The actual delays depend on line speed and system load.
.Ss "Control Modes"
The
.Fa c_cflag
field describes the hardware control of the terminal:
.Bl -tag -width CIBAUDEXT -offset 2n
.It Dv CBAUD
Baud rate:
.Bl -tag -width B4000000 -compact
.It Dv B0
Hang up
.It Dv B50
50 baud
.It Dv B75
75 baud
.It Dv B110
110 baud
.It Dv B134
134 baud
.It Dv B150
150 baud
.It Dv B200
200 baud
.It Dv B300
300 baud
.It Dv B600
600 baud
.It Dv B1200
1200 baud
.It Dv B1800
1800 baud
.It Dv B2400
2400 baud
.It Dv B4800
4800 baud
.It Dv B9600
9600 baud
.It Dv B19200
19200 baud
.It Dv B38400
38400 baud
.It Dv B57600
57600 baud
.It Dv B76800
76800 baud
.It Dv B115200
115200 baud
.It Dv B153600
153600 baud
.It Dv B230400
230400 baud
.It Dv B307200
307200 baud
.It Dv B460800
460800 baud
.It Dv B921600
921600 baud
.It Dv B1000000
1000000 baud
.It Dv B1152000
1152000 baud
.It Dv B1500000
1500000 baud
.It Dv B2000000
2000000 baud
.It Dv B2500000
2500000 baud
.It Dv B3000000
3000000 baud
.It Dv B3500000
3500000 baud
.It Dv B4000000
4000000 baud
.El
.It Dv CSIZE
Character size:
.Bl -tag -width CIBAUDEXT -compact
.It Dv CS5
5 bits
.It Dv CS6
6 bits
.It Dv CS7
7 bits
.It Dv CS8
8 bits
.It Dv CSTOPB
Send two stop bits, else one
.It Dv CREAD
Enable receiver
.It Dv PARENB
Parity enable
.It Dv PARODD
Odd parity, else even
.It Dv HUPCL
Hang up on last close
.It Dv CLOCAL
Local line, else dial-up
.It Dv CIBAUD
Input baud rate, if different from output rate
.It Dv PAREXT
Extended parity for mark and space parity
.It Dv CRTSXOFF
Enable inbound hardware flow control
.It Dv CRTSCTS
Enable outbound hardware flow control
.It Dv CBAUDEXT
Bit to indicate output speed > B38400
.It Dv CIBAUDEXT
Bit to indicate input speed > B38400
.El
.El
.Pp
The
.Dv CBAUD
bits together with the
.Dv CBAUDEXT
bit specify the output baud rate.
To retrieve the output speed from the
.Vt termios
structure pointed to by
.Fa termios_p
see the following code segment.
.Bd -literal -offset 2n
speed_t ospeed;
if (termios_p->c_cflag & CBAUDEXT)
 ospeed = (termios_p->c_cflag & CBAUD) + CBAUD + 1;
else
 ospeed = termios_p->c_cflag & CBAUD;
.Ed
.Pp
To store the output speed in the termios structure pointed to by
.Fa termios_p
see the following code segment.
.Bd -literal -offset 2n
speed_t ospeed;
if (ospeed > CBAUD) {
 termios_p->c_cflag |= CBAUDEXT;
 ospeed -= (CBAUD + 1);
} else {
 termios_p->c_cflag &= ~CBAUDEXT;
}
termios_p->c_cflag =
  (termios_p->c_cflag & ~CBAUD) | (ospeed & CBAUD);
.Ed
.Pp
The zero baud rate,
.Dv B0 ,
is used to hang up the connection.
If
.Dv B0
is specified, the data-terminal-ready signal is not asserted.
Normally, this disconnects the line.
.Pp
If the
.Dv CIBAUDEXT
or
.Dv CIBAUD
bits are not zero, they specify the input baud rate, with the
.Dv CBAUDEXT
and
.Dv CBAUD
bits specifying the output baud rate; otherwise, the output and input baud
rates are both specified by the
.Dv CBAUDEXT
and
.Dv CBAUD
bits.
The values for the
.Dv CIBAUD
bits are the same as the values for the
.Dv CBAUD
bits, shifted left
.Dv IBSHIFT
bits.
For any particular hardware, impossible speed changes are
ignored.
To retrieve the input speed in the
.Vt termios
structure pointed to
by
.Fa termios_p
see the following code segment.
.Bd -literal -offset 2n
speed_t ispeed;
if (termios_p->c_cflag & CIBAUDEXT) {
 ispeed = ((termios_p->c_cflag & CIBAUD) >> IBSHIFT)
 + (CIBAUD >> IBSHIFT) + 1;
} else {
 ispeed = (termios_p->c_cflag & CIBAUD) >> IBSHIFT;
}
.Ed
.Pp
To store the input speed in the
.Vt termios
structure pointed to by
.Fa termios_p
see the following code segment.
.Bd -literal -offset 2n
speed_t ispeed;
if (ispeed == 0) {
 ispeed = termios_p->c_cflag & CBAUD;
 if (termios_p->c_cflag & CBAUDEXT)
     ispeed += (CBAUD + 1);
}
if ((ispeed << IBSHIFT) > CIBAUD) {
  termios_p->c_cflag |= CIBAUDEXT;
  ispeed -= ((CIBAUD >> IBSHIFT) + 1);
} else {
  termios_p->c_cflag &= ~CIBAUDEXT;
}
termios_p->c_cflag =
  (termios_p->c_cflag & ~CIBAUD) | ((ispeed << IBSHIFT) & CIBAUD);
.Ed
.Pp
The
.Dv CSIZE
bits specify the character size in bits for both transmission and reception.
This size does not include the parity bit, if any.
If
.Dv CSTOPB
is set, two stop bits are used; otherwise, one stop bit is used.
For example, at 110 baud, two stops bits are required.
.Pp
If
.Dv PARENB
is set, parity generation and detection is enabled, and a
parity bit is added to each character.
If parity is enabled, the
.Dv PARODD
flag specifies odd parity if set; otherwise, even parity is used.
.Pp
If
.Dv CREAD
is set, the receiver is enabled.
Otherwise, no characters are received.
.Pp
If
.Dv HUPCL
is set, the line is disconnected when the last process with the
line open closes it or terminates.
That is, the data-terminal-ready signal is not asserted.
.Pp
If
.Dv CLOCAL
is set, the line is assumed to be a local, direct connection
with no modem control; otherwise, modem control is assumed.
.Pp
If
.Dv CRTSXOFF
is set, inbound hardware flow control is enabled.
.Pp
If
.Dv CRTSCTS
is set, outbound hardware flow control is enabled.
.Pp
The four possible combinations for the state of
.Dv CRTSCTS
and
.Dv CRTSXOFF
bits and their interactions are described below.
.Bl -tag -width "Case C:"
.It Sy Case A :
.Dv CRTSCTS
off,
.Dv CRTSXOFF
off.
In this case the hardware flow control is disabled.
.It Sy Case B :
.Dv CRTSCTS
on,
.Dv CRTSXOFF
off.
In this case only outbound hardware flow control is enabled.
The state of CTS signal is used to do outbound flow control.
It is expected that output will be suspended if CTS is low and resumed
when CTS is high.
.It Sy Case C :
.Dv CRTSCTS
off,
.Dv CRTSXOFF
on.
In this case only inbound hardware flow control is enabled.
The state of RTS signal is used to do inbound flow control.
It is expected that input will be suspended if RTS is low and resumed when RTS
is high.
.It Sy Case D :
.Dv CRTSCTS
on,
.Dv CRTSXOFF
on.
In this case both inbound and outbound hardware flow control are enabled.
Uses the state of CTS signal to do outbound
flow control and RTS signal to do inbound flow control.
.El
.Ss "Local Modes"
The
.Fa c_lflag
field of the argument structure is used by the line
discipline to control terminal functions.
The basic line discipline provides the following:
.Pp
.Bl -tag -offset 2n -width SIGTTOU -compact
.It Dv ISIG
Enable signals.
.It Dv ICANON
Canonical input (erase and kill processing).
.It Dv XCASE
Canonical upper/lower presentation.
.It Dv ECHO
Enable echo.
.It Dv ECHOE
Echo erase character as
.Sy BS Ns - Ns Sy SP Ns - Ns Sy BS
&.
.It Dv ECHOK
Echo
.Sy NL
after kill character.
.It Dv ECHONL
Echo
.Sy NL .
.It Dv NOFLSH
Disable flush after interrupt or quit.
.It Dv TOSTOP
Send
.It Dv SIGTTOU
for background output.
.It Dv ECHOCTL
Echo control characters as
.Em char ,
delete as ^?.
.It Dv ECHOPRT
Echo erase character as character erased.
.It Dv ECHOKE
.Sy BS Ns - Ns Sy SP Ns - Ns Sy BS
erase entire line on line kill.
.It Dv FLUSHO
Output is being flushed.
.It Dv PENDIN
Retype pending input at next read or input character.
.It Dv IEXTEN
Enable extended (implementation-defined) functions.
.El
.Pp
If
.Dv ISIG
is set, each input character is checked against the special
control characters
.Sy INTR ,
.Sy QUIT ,
.Sy SWTCH ,
.Sy SUSP ,
.Sy STATUS ,
and
.Sy DSUSP .
If an input character matches one of these control characters, the function
associated with that character is performed.
.Po
Note: If
.Sy SWTCH
is set and the character matches, the character is simply discarded.
No other action is taken.
.Pc
If
.Dv ISIG
is not set, no checking is done.
Thus, these special
input functions are possible only if
.Dv ISIG
is set.
.Pp
If
.Dv ICANON
is set, canonical processing is enabled.
This enables the erase
and kill edit functions, and the assembly of input characters into lines
delimited by
.Sy NL-c ,
.Sy EOF ,
.Sy EOL ,
and
.Sy EOL .
If
.Dv ICANON
is not set, read requests are satisfied directly from the input queue.
A read is not satisfied until at least
.Sy MIN
characters have been received or the timeout value
.Sy TIME
has expired between characters.
This allows fast bursts of input to be read efficiently while still allowing
single character input.
The time value represents tenths of seconds.
.Pp
If
.Dv XCASE
is set and
.Dv ICANON
is set, an upper case letter is
accepted on input if preceded by a backslash
.Ql \e
character, and is output preceded by a backslash
.Ql \e
character.
In this mode, the
following escape sequences are generated on output and accepted on input:
.Bl -column "FOR:" "USE:" -offset 2n
.It FOR: Ta USE:
.It ` Ta \e'
.It | Ta \e!
.It \(ap Ta \e^
.It { Ta \e(
.It } Ta \e)
.It \e Ta \e\e
.El
.Pp
For example, input A as \ea, \en as \e\en, and \eN as \e\e\en.
.Pp
If
.Dv ECHO
is set, characters are echoed as received.
.Pp
When
.Dv ICANON
is set, the following echo functions are possible.
.Bl -bullet -offset indent
.It
If
.Dv ECHO
and
.Dv ECHOE
are set, and
.Dv ECHOPRT
is not set, the
.Sy ERASE ,
.Sy ERASE2 ,
and
.Sy WERASE
characters are echoed as one or
more ASCII BS SP BS, which clears the last character(s) from a
.Sy CRT
screen.
.It
If
.Dv ECHO ,
.Dv ECHOPRT ,
and
.Dv IEXTEN
are set, the first
.Sy ERASE ,
.Sy ERASE2 ,
and
.Sy WERASE
character in a sequence echoes as a backslash
.Ql \e ,
followed by the characters being erased.
Subsequent
.Sy ERASE
and
.Sy WERASE
characters echo the characters being erased, in reverse order.
The
next non-erase character causes a
.Ql /
(slash) to be typed before it is echoed.
.Dv ECHOPRT
should be used for hard copy terminals.
.It
If
.Dv ECHOKE
and
.Dv IEXTEN
are set, the kill character is echoed by
erasing each character on the line from the screen (using the mechanism
selected by
.Dv ECHOE
and
.Dv ECHOPR ) .
.It
If
.Dv ECHOK
is set, and
.Dv ECHOKE
is not set, the
.Sy NL
character is
echoed after the kill character to emphasize that the line is deleted.
Note
that a
.Ql \e
(escape) character or an
.Sy LNEXT
character preceding the erase
or kill character removes any special function.
.It
If
.Dv ECHONL
is set, the
.Sy NL
character is echoed even if
.Dv ECHO
is not set.
This is useful for terminals set to local echo (so called
half-duplex).
.El
.Pp
If
.Dv ECHOCTL
and
.Dv IEXTEN
are set, all control characters (characters
with codes between 0 and 37 octal) other than
.Sy ASCII TAB ,
.Sy ASCII NL ,
the
.Sy START
character, and the
.Sy STOP
character,
.Sy ASCII CR ,
and
.Sy ASCII BS
are echoed as
.No ^ Ns Em X ,
where
.Em X
is the character given by adding
.Ql 100
octal to the code of the control character (so
that the character with octal code
.Ql 1
is echoed as
.No ^ Ns Sy A ) ,
and the
.Sy ASCII DEL
character,
with code
.Ql 177
octal, is echoed as
.No ^ Ns Sy \&? .
.Pp
If
.Dv NOFLSH
is set, the normal flush of the input and output queues
associated with the
.Sy INTR ,
.Sy QUIT ,
.Sy STATUS ,
and
.Sy SUSP
characters is not done.
This bit should be set when restarting system calls
that read from or write to a terminal
.Po
see
.Xr sigaction 2
.Pc .
.Pp
If
.Dv TOSTOP
and
.Dv IEXTEN
are set, the signal
.Dv SIGTTOU
is sent to
a process that tries to write to its controlling terminal if it is not in the
foreground process group for that terminal.
This signal normally stops the process.
Otherwise, the output generated by that process is output to the
current output stream.
Processes that are blocking or ignoring
.Dv SIGTTOU
signals are excepted and allowed to produce output, if any.
.Pp
If
.Dv FLUSHO
and
.Dv IEXTEN
are set, data written to the terminal is
discarded.
This bit is set when the
.Sy FLUSH
character is typed.
A program can cancel the effect of typing the
.Sy FLUSH
character by clearing
.Dv FLUSHO .
.Pp
If
.Dv PENDIN
and
.Dv IEXTEN
are set, any input that has not yet been read
is reprinted when the next character arrives as input.
.Dv PENDIN
is then
automatically cleared.
.Pp
If
.Dv IEXTEN
is set, the following implementation-defined functions are
enabled: special characters (
.Sy WERASE ,
.Sy REPRINT ,
.Sy DISCARD ,
and
.Sy LNEXT )
and local flags (
.Dv TOSTOP ,
.Dv ECHOCTL ,
.Dv ECHOPRT ,
.Dv ECHOKE ,
.Dv FLUSHO ,
and
.Dv PENDIN ) .
.Ss "Minimum and Timeout"
The
.Sy MIN
and
.Sy TIME
values were described previously, in the
subsection,
.Sy Non-canonical Mode Input Processing .
The initial value of
.Sy MIN
is 1, and the initial value of
.Sy TIME
is 0.
.Ss "Terminal Size"
The number of lines and columns on the terminal's display is specified in the
.Vt winsize
structure defined by
.In sys/termios.h
and includes the following members:
.Bd -literal -offset 2n
unsigned	short ws_row;  /* rows, in characters */
unsigned short	ws_col;        /* columns, in characters */
unsigned short	ws_xpixel;     /* horizontal size, in pixels */
unsigned short	ws_ypixel;     /* vertical size, in pixels */
.Ed
.Ss "Termio Structure"
The SunOS/SVR4
.Vt termio
structure is used by some
.Fn ioctl Ns s ;
it is defined by
.In sys/termio.h
and includes the following members:
.Bd -literal -offset 2n
unsigned	short	c_iflag;    /* input modes */
unsigned	short	c_oflag;    /* output modes */
unsigned	short	c_cflag;    /* control modes */
unsigned	short	c_lflag;    /* local modes */
char			c_line;     /* line discipline */
unsigned	char	c_cc[NCC];  /* control chars */
.Ed
.Pp
The special control characters are defined by the array
.Fa c_cc .
The symbolic name
.Dv NCC
is the size of the Control-character array and is also
defined by
.In termio.h .
The relative positions, subscript names, and typical
default values for each function are as follows:
.Bl -column "Relative Positions" "Subscript Names" "Typical Default Values"
.It Relative Positions Ta Subscript Names Ta Typical Default Values
.It 0 Ta VINTR Ta EXT
.It 1 Ta VQUIT Ta FS
.It 2 Ta VERASE Ta DEL
.It 3 Ta VKILL Ta NAK
.It 4 Ta VEOF Ta EOT
.It 5 Ta VEOL Ta NUL
.It 6 Ta VEOL2 Ta NUL
.It 7 Ta Reserved Ta
.El
.Pp
The
.Sy MIN
values is stored in the
.Dv VMIN
element of the
.Fa c_cc
array; the
.Sy TIME
value is stored in the
.Dv VTIME
element of the
.Fa c_cc
array.
The
.Dv VMIN
element is the same element as the
.Dv VEOF
element; the
.Dv VTIME
element is the same element as the
.Dv VEOL
element.
.Pp
The calls that use the
.Va termio
structure only affect the flags and control
characters that can be stored in the
.Vt termio
structure; all other flags and control characters are unaffected.
.Ss "Modem Lines"
On special files representing serial ports, modem control lines can be read.
Control lines (if the underlying hardware supports it) may also be changed.
Status lines are read-only.
The following modem control and status lines may be
supported by a device; they are defined by
.In sys/termios.h :
.Pp
.Bl -tag -width "TIOCM_DTR" -compact -offset 2n
.It Dv TIOCM_LE
line enable
.It Dv TIOCM_DTR
data terminal ready
.It Dv TIOCM_RTS
request to send
.It Dv TIOCM_ST
secondary transmit
.It Dv TIOCM_SR
secondary receive
.It Dv TIOCM_CTS
clear to send
.It Dv TIOCM_CAR
carrier detect
.It Dv TIOCM_RNG
ring
.It Dv TIOCM_DSR
data set ready
.El
.Pp
.Dv TIOCM_CD
is a synonym for
.Dv TIOCM_CAR ,
and
.Dv TIOCM_RI
is a synonym for
.Dv TIOCM_RNG .
Not all of these are necessarily supported by any
particular device; check the manual page for the device in question.
.Pp
The software carrier mode can be enabled or disabled using the
.Dv TIOCSSOFTCAR
.Fn ioctl .
If the software carrier flag for a line is off,
the line pays attention to the hardware carrier detect (DCD) signal.
The
.Sy tty
device associated with the line cannot be opened until
.Sy DCD
is asserted.
If the software carrier flag is on, the line behaves as if
.Sy DCD
is always asserted.
.Pp
The software carrier flag is usually turned on for locally connected terminals
or other devices, and is off for lines with modems.
.Pp
To be able to issue the
.Dv TIOCGSOFTCAR
and
.Dv TIOCSSOFTCAR
.Fn ioctl
calls, the
.Sy tty
line should be opened with
.Dv O_NDELAY
so that the
.Xr open 2
will not wait for the carrier.
.Ss "Default Values"
The initial
.Vt termios
values upon driver open is configurable.
This is accomplished by setting the "ttymodes" property in the file
.Pa /kernel/drv/options.conf .
Since this property is assigned during system
initialization, any change to the "ttymodes" property will not take effect
until the next reboot.
The string value assigned to this property should be in
the same format as the output of the
.Xr stty 1
command with the -g option.
.Pp
If this property is undefined, the following
.Vt termios
modes are in effect.
The initial input control value is
.Dv BRKINT ,
.Dv ICRNL ,
.Dv IXON ,
.Dv IMAXBEL .
The initial output control value is
.Dv OPOST ,
.Dv ONLCR ,
.Dv TAB3 .
The initial hardware control value is
.Dv B9600 ,
.Dv CS8 ,
.Dv CREAD .
The initial line-discipline control value is
.Dv ISIG ,
.Dv ICANON ,
.Dv IEXTEN ,
.Dv ECHO ,
.Dv ECHOK ,
.Dv ECHOE ,
.Dv ECHOKE ,
.Dv ECHOCTL .
.Sh IOCTLS
The
.Fn ioctl Ns s
supported by devices and
.Sy STREAMS
modules providing the
.Xr termios 3C
interface are listed below.
Some calls may not be supported by all devices or modules.
The functionality provided by these calls is also
available through the preferred function call interface specified on
.Nm termios .
.Bl -tag -width TIOCSSOFTCAR
.It Dv TCGETS
The argument is a pointer to a
.Vt termios
structure.
The current terminal parameters are fetched and stored into that structure.
.It Dv TCSETS
The argument is a pointer to a
.Vt termios
structure.
The current terminal parameters are set from the values stored in that structure.
The change is immediate.
.It Dv TCSETSW
The argument is a pointer to a
.Vt termios
structure.
The current terminal parameters are set from the values stored in that structure.
The change occurs after all characters queued for output have been transmitted.
This form should be used when changing parameters that affect output.
.It Dv TCSETSF
The argument is a pointer to a
.Vt termios
structure.
The current terminal parameters are set from the values stored in that structure.
The change occurs after all characters queued for output have been transmitted;
all characters queued for input are discarded and then the change occurs.
.It Dv TCGETA
The argument is a pointer to a
.Vt termio
structure.
The current terminal parameters are fetched, and those parameters that can be
stored in a
.Vt termio
structure are stored into that structure.
.It Dv TCSETA
The argument is a pointer to a
.Vt termio
structure.
Those terminal parameters that can be stored in a
.Vt termio
structure are set from the values stored in that structure.
The change is immediate.
.It Dv TCSETAW
The argument is a pointer to a
.Vt termio
structure.
Those terminal parameters that can be stored in a
.Vt termio
structure are set from
the values stored in that structure.
The change occurs after all characters queued for output have been transmitted.
This form should be used when changing parameters that affect output.
.It Dv TCSETAF
The argument is a pointer to a
.Vt termio
structure.
Those terminal parameters that can be stored in a
.Vt termio
structure are set from the values stored in that structure.
The change occurs after all characters queued
for output have been transmitted; all characters queued for input are discarded
and then the change occurs.
.It Dv TCSBRK
The argument is an
.Vt int
value.
Wait for the output to drain.
If the argument is
.Sy 0 ,
then send a break (zero valued bits for 0\&.25 seconds).
.It Dv TCXONC
Start/stop control.
The argument is an
.Vt int
value.
If the argument is
.Sy 0 ,
suspend output; if
.Sy 1 ,
restart suspended output; if
.Sy 2 ,
suspend input; if
.Sy 3 ,
restart suspended input.
.It Dv TCFLSH
The argument is an
.Vt int
value.
If the argument is
.Sy 0 ,
flush the input queue; if
.Sy 1 ,
flush the output queue; if
.Sy 2 ,
flush both the input and output queues.
.It Dv TIOCGPGRP
The argument is a pointer to a
.Vt pid_t .
Set the value of that
.Vt pid_t
to the process group
.Sy ID
of the foreground process group associated with the terminal.
See
.Xr termios 3C
for a description of
.Dv TCGETPGRP .
.It Dv TIOCSPGRP
The argument is a pointer to a
.Vt pid_t .
Associate the process group whose
process group
.Sy ID
is specified by the value of that
.Vt pid_t
with the terminal.
The new process group value must be in the range of valid process
group
.Sy ID
values.
Otherwise, the error
.Er EPERM
is returned.
.It Dv TIOCGSID
The argument is a pointer to a
.Vt pid_t .
The session ID of the terminal is fetched and stored in the
.Vt pid_t .
.It Dv TIOCGWINSZ
The argument is a pointer to a
.Vt winsize
structure.
The terminal driver's
notion of the terminal size is stored into that structure.
.It Dv TIOCSWINSZ
The argument is a pointer to a
.Vt winsize
structure.
The terminal driver's
notion of the terminal size is set from the values specified in that structure.
If the new sizes are different from the old sizes, a
.Dv SIGWINCH
signal is set to the process group of the terminal.
.It Dv TIOCMBIS
The argument is a pointer to an
.Vt int
whose value is a mask containing modem control lines to be turned on.
The control lines whose bits are set in
the argument are turned on; no other control lines are affected.
.It Dv TIOCMBIC
The argument is a pointer to an
.Vt int
whose value is a mask containing modem control lines to be turned off.
The control lines whose bits are set in
the argument are turned off; no other control lines are affected.
.It Dv TIOCMGET
The argument is a pointer to an
.Vt int .
The current state of the modem
status lines is fetched and stored in the
.Vt int
pointed to by the argument.
.It Dv TIOCMSET
The argument is a pointer to an
.Vt int
containing a new set of modem control lines.
The modem control lines are turned on or off, depending on
whether the bit for that mode is set or clear.
.It Dv TIOCSPPS
The argument is a pointer to an
.Vt int
that determines whether pulse-per-second event handling is to be enabled
(non-zero) or disabled (zero).
If a one-pulse-per-second reference clock is attached to the serial line's data
carrier detect input, the local system clock will be calibrated to it.
A clock with a high error, that is, a deviation of more than 25 microseconds
per tick, is ignored.
.It Dv TIOCGPPS
The argument is a pointer to an
.Vt int ,
in which the state of the even handling is returned.
The
.Vt int
is set to a non-zero value if pulse-per-second (PPS) handling has been enabled.
Otherwise, it is set to zero.
.It Dv TIOCGSOFTCAR
The argument is a pointer to an
.Vt int
whose value is
.Sy 1
or
.Sy 0 ,
depending on whether the software carrier detect is turned on or off.
.It Dv TIOCSSOFTCAR
The argument is a pointer to an
.Vt int
whose value is
.Sy 1
or
.Sy 0 .
The value of the integer should be
.Sy 0
to turn off software carrier, or
.Sy 1
to turn it on.
.It Dv TIOCGPPSEV
The argument is a pointer to a
.Vt "struct ppsclockev" .
This structure contains the following members:
.Bd -literal -offset 2n
struct timeval tv;
uint32_t serial;
.Ed
.Pp
.Fa tv
is the system clock timestamp when the event (pulse on the
.Sy DCD
pin) occurred.
.Fa serial
is the ordinal of the event, which each consecutive event
being assigned the next ordinal.
The first event registered gets a
.Fa serial
value of
.Sy 1 .
The
.Dv TIOCGPPSEV
returns the last event registered; multiple calls will persistently return the
same event until a new one is registered.
In addition to time stamping and saving the event, if it is of
one-second period and of consistently high accuracy, the local system clock
will automatically calibrate to it.
.El
.Sh FILES
Files in or under
.Pa /dev
.Sh SEE ALSO
.Xr stty 1 ,
.Xr fork 2 ,
.Xr getpgid 2 ,
.Xr getsid 2 ,
.Xr ioctl 2 ,
.Xr setsid 2 ,
.Xr sigaction 2 ,
.Xr signal 3C ,
.Xr tcsetpgrp 3C ,
.Xr termios 3C ,
.Xr signal.h 3HEAD ,
.Xr streamio 4I