TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
NAME
termio - general terminal interface
SYNOPSIS
#include <termio.h>
ioctl(int fildes, int request, struct termio *arg);
ioctl(int fildes, int request, int arg);
#include <termios.h>
ioctl(int fildes, int request, struct termios *arg);
DESCRIPTION
System V supports a general interface for asynchronous com-
munications ports that is hardware-independent. The user
interface to this functionality is via function calls (the
preferred interface) described in termios(2) or ioctl com-
mands described in this section. This section also
discusses the common features of the terminal subsystem
which are relevant with both user interfaces.
When a terminal file is opened, it normally causes the pro-
cess to wait until a connection is established. In prac-
tice, users' programs seldom open terminal files; they are
opened by the system and become a user's standard input,
output, and error files. The very first terminal file
opened by the session leader, which is not already associ-
ated 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 fork(2). A process can break this association by
changing its session using setsid(2).
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 com-
pletely full, which is rare (e.g., if the number of charac-
ters in the line discipline buffer exceeds {MAXCANON} and
IMAXBEL [see below] is not set), or when the user has accu-
mulated {MAXINPUT} 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.
Session management (Job Control)
A control terminal will distinguish one of the process
groups in the session associated with it to be the fore-
ground process group. All other process groups in the ses-
sion are designated as background process groups. This
Printed 11/19/92 Page 1
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
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 con-
trolling process's process group is assigned as foreground
process group.
Background process groups in the controlling process's ses-
sion 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. These are pro-
cess groups which do not have a member with a parent in
another process group that is in the same session and there-
fore shares the same controlling terminal. When a member's
orphaned process group attempts to access its controlling
terminal, errors will be returned. since there is no pro-
cess to continue it if it should stop.
If a member of a background process group attempts to read
its controlling terminal, its process group will be sent a
SIGTTIN signal, which will normally cause the members of
that process group to stop. If, however, the process is
ignoring or holding SIGTTIN, or is a member of an orphaned
process group, the read will fail with errno set to EIO, and
no signal will be sent.
If a member of a background process group attempts to write
its controlling terminal and the TOSTOP bit is set in the
clflag field, its process group will be sent a SIGTTOU sig-
nal, which will normally cause the members of that process
group to stop. If, however, the process is ignoring or
holding SIGTTOU, the write will succeed. If the process is
not ignoring or holding SIGTTOU and is a member of an
orphaned process group, the write will fail with errno set
to EIO, and no signal will be sent.
If TOSTOP is set and a member of a background process group
attempts to ioctl its controlling terminal, and that ioctl
will modify terminal parameters (e.g., TCSETA, TCSETAW,
TCSETAF, or TIOCSPGRP), its process group will be sent a
SIGTTOU signal, which will normally cause the members of
that process group to stop. If, however, the process is
ignoring or holding SIGTTOU, the ioctl will succeed. If the
process is not ignoring or holding SIGTTOU and is a member
of an orphaned process group, the write will fail with errno
set to EIO, and no signal will be sent.
Canonical mode input processing
Normally, terminal input is processed in units of lines. A
line is delimited by a newline (ASCII LF) character, an
end-of-file (ASCII EOT) character, or an end-of-line
Page 2 Printed 11/19/92
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
character. This means that a program attempting to read
will be suspended 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.
During input, erase and kill processing is normally done.
The ERASE character (by default, the character number #)
erases the last character typed. The WERASE character (the
character control-W) erases the last ``word'' typed in the
current input line (but not any preceding spaces or tabs).
A ``word'' is defined as a sequence of non-blank characters,
with tabs counted as blanks. Neither ERASE nor WERASE will
erase beyond the beginning of the line. The KILL character
(by default, the character @) 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
REPRINT character (the character 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 pro-
gram output. The characters are reprinted as if they were
being echoed; consequencely, if ECHO is not set, they are
not printed.
The ERASE and KILL characters may be entered literally by
preceding them with the escape character (\). In this case,
the escape character is not read. The erase and kill char-
acters may be changed.
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 MIN and TIME values are used to determine
how to process the characters received.
MIN represents the minimum number of characters that should
be received when the read is satisfied (i.e., when the char-
acters are returned to the user). 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
MIN and TIME and their interactions are described below.
Case A: MIN > 0, TIME > 0
In this case, 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 charac-
ter is received. The interaction between MIN and TIME is
as follows: as soon as one character is received, the
Printed 11/19/92 Page 3
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
intercharacter timer is started. If 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 MIN
characters are received, the characters received to that
point are returned to the user. Note that if 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 MIN and 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.
Case B: MIN > 0, TIME = 0
In this case, since the value of TIME is zero, the timer
plays no role and only MIN is significant. A pending read
is not satisfied until MIN characters are received (the
pending read sleeps until MIN characters are received). A
program that uses this case to read record based terminal
I/O may block indefinitely in the read operation.
Case C: MIN = 0, TIME > 0
In this case, since MIN = 0, TIME no longer represents an
intercharacter timer: it now serves as a read timer that
is activated as soon as a read is done. A read is satis-
fied 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 charac-
ter is received within TIME*.10 seconds after the read is
initiated, the read returns with zero characters.
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 char-
acters currently available is returned without waiting for
more characters to be input.
Comparison of the different cases of MIN, TIME interaction
Some points to note about MIN and TIME:
1. In the following explanations, note that the interac-
tions of MIN and TIME are not symmetric. For example,
when MIN > 0 and TIME = 0, TIME has no effect. However,
in the opposite case, where MIN = 0 and TIME > 0, both
MIN and TIME play a role in that MIN is satisfied with
the receipt of a single character.
Page 4 Printed 11/19/92
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
2. Also note that in case A (MIN > 0, TIME > 0), TIME
represents an intercharacter timer, whereas in case C
(TIME = 0, TIME > 0), TIME represents a read timer.
These two points highlight the dual purpose of the MIN/TIME
feature. Cases A and B, where MIN > 0, exist to handle
burst mode activity (e.g., file transfer programs), where a
program would like to process at least 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.
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.
Another important note is that MIN is always just a minimum.
It does not denote a record length. For example, if a pro-
gram does a read of 20 bytes, MIN is 10, and 25 characters
are present, then 20 characters will be returned to the
user.
Writing characters
When one or more characters are written, they are transmit-
ted to the terminal as soon as previously written characters
have finished typing. Input characters are echoed as they
are typed if echoing has been enabled. If a process pro-
duces 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 pro-
gram is resumed.
Special characters
Certain characters have special functions on input. These
functions and their default character values are summarized
as follows:
INTR (Rubout or ASCII DEL) generates a SIGINT signal.
SIGINT is sent to all frequent processes associ-
ated with the controlling terminal. Normally,
each such process is forced to terminate, but
arrangements may be made either to ignore the sig-
nal or to receive a trap to an agreed upon loca-
tion. [See signal(5)].
QUIT (CTRL-| or ASCII FS) generates a 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 core) will be
Printed 11/19/92 Page 5
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
created in the current working directory.
ERASE (#) erases the preceding character. It does not
erase beyond the start of a line, as delimited by
a NL, EOF, EOL, or EOL2 character.
WERASE (CTRL-W or ASCII ETX) erases the preceding
``word''. It does not erase beyond the start of a
line, as delimited by a NL, EOF, EOL, or EOL2
character.
KILL (@) deletes the entire line, as delimited by a NL,
EOF, EOL, or EOL2 character.
REPRINT (CTRL-R or ASCII DC2) reprints all characters,
preceded by a newline, that have not been read.
EOF (CTRL-D or 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 new-
line, and the EOF is discarded. Thus, if no char-
acters are waiting (i.e., the EOF occurred at the
beginning of a line) zero characters are passed
back, which is the standard end-of-file indica-
tion. Unless escaped, the EOF character is not
echoed. Because EOT is the default EOF character,
this prevents terminals that respond to EOT from
hanging up.
NL (ASCII LF) is the normal line delimiter. It can-
not be changed or escaped.
EOL (ASCII NULL) is an additional line delimiter, like
NL. It is not normally used.
EOL2 is another additional line delimiter.
SWTCH (CTRL-Z or ASCII EM) is used only when shl layers
is invoked.
SUSP (CTRL-Z or ASCII SUB) generates a SIGTSTP signal.
SIGTSTP stops all processes in the foreground pro-
cess group for that terminal.
DSUSP (CTRL-Y or ASCII EM) It generates a SIGTSTP signal
as SUSP does, but the signal is sent when a pro-
cess in the foreground process group attempts to
read the DSUSP character, rather than when it is
typed.
STOP (CTRL-S or ASCII DC3) can be used to suspend
Page 6 Printed 11/19/92
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
output temporarily. It is useful with CRT termi-
nals to prevent output from disappearing before it
can be read. While output is suspended, STOP char-
acters are ignored and not read.
START (CTRL-Q or ASCII DC1) is used to resume output.
Output has been suspended by a STOP character.
While output is not suspended, START characters
are ignored and not read.
DISCARD (CTRL-O or ASCII SI) causes subsequent output to
be discarded. Output is discarded until another
DISCARD character is typed, more input arrives, or
the condition is cleared by a program.
LNEXT (CTRL-V or 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 other-
wise be interpreted by the system (e.g. KILL,
QUIT).
The character values for INTR, QUIT, ERASE, WERASE, KILL,
REPRINT, EOF, EOL, EOL2, SWTCH, SUSP, DSUSP, STOP, START,
DISCARD, and LNEXT may be changed to suit individual tastes.
If the value of a special control character is
_POSIX_VDISABLE (0), the function of that special control
character is disabled. The ERASE, KILL, and EOF characters
may be escaped by a preceding \ character, in which case no
special function is done. Any of the special characters may
be preceded by the LNEXT character, in which case no special
function is done.
Modem disconnect
When a modem disconnect is detected, a SIGHUP signal is sent
to the terminal's controlling process. Unless other arrange-
ments have been made, these signals cause the process to
terminate. If SIGHUP is ignored or caught, any subsequent
read returns with an end-of-file indication until the termi-
nal is closed.
If the controlling process is not in the foreground process
group of the terminal, a SIGTSTP is sent to the terminal's
foreground process group. Unless other arrangements have
been made, these signals cause the processes to stop.
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 SIGTTOU and SIGTTIN signals. Unless other
arrangements have been made, this signal causes the
processes to stop.
Printed 11/19/92 Page 7
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
The controlling terminal will remain in this state until it
is reinitialized with a successful open by the controlling
process, or deallocated by the controlling process.
Terminal parameters
The parameters that control the behavior of devices and
modules providing the termios interface are specified by the
termios structure defined by <termios.h>. Several ioctl(2)
system calls that fetch or change these parameters use this
structure that contains the following members:
tcflagt ciflag; /* input modes */
tcflagt coflag; /* output modes */
tcflagt ccflag; /* control modes */
tcflagt clflag; /* local modes */
cct ccc[NCCS]; /* control chars */
The special control characters are defined by the array
ccc. The symbolic name NCCS is the size of the control-
character array and is also defined by <termios.h>. The
relative positions, subscript names, and typical default
values for each function are as follows:
0 VINTR DEL
1 VQUIT FS
2 VERSE #
3 VKILL @
4 VEOF EOT
5 VEOL NUL
6 VEOL2 NUL
7 VSWTCH NUL
8 VSTRT DC1
9 VSTOP DC3
10 VSUSP SUB
11 VDSUSP EM
12 VREPRINT DC2
13 VDISCRD SI
14 VWERSE ETB
15 VLNEXT SYN
16-19 reserved
Input modes
The ciflag field describes the basic terminal input con-
trol:
IGNBRK Ignore break condition.
BRKINT Signal interrupt on break.
IGNPAR Ignore characters with parity errors.
PARMRK Mark parity errors.
INPCK Enable input parity check.
ISTRIP Strip character.
INLCR Map NL to CR on input.
IGNCR Ignore CR.
Page 8 Printed 11/19/92
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
ICRNL Map CR to NL on input.
IUCLC Map upper-case to lower-case on input.
IXON Enable start/stop output control.
IXANY Enable any character to restart output.
IXOFF Enable start/stop input control.
IMAXBEL Echo BEL on input line too long.
If 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 IGNBRK is not set and 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 SIGINT
signal to that foreground process group. If neither IGNBRK
nor BRKINT is set, a break condition is read as a single
ASCII NULL character ('\0'), or if PARMRK is set, as '\377',
'\0', '\0'.
If IGNPAR is set, a byte with framing or parity errors
(other than break) is ignored.
If PARMRK is set, and IGNPAR is not set, a byte with a fram-
ing or parity error (other than break) is given to the
application as the three-character sequence: '\377', '\0',
X, where X is the data of the byte received in error. To
avoid ambiguity in this case, if ISTRIP is not set, a valid
character of '\377' is given to the application as '\377',
'\377'. If neither IGNPAR nor PARMRK is set, a framing or
parity error (other than break) is given to the application
as a single ASCII NULL character ('\0').
If INPCK is set, input parity checking is enabled. If 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 dis-
abled. 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.
If ISTRIP is set, valid input characters are first stripped
to seven bits, otherwise all eight bits are processed.
If INLCR is set, a received NL character is translated into
a CR character. If IGNCR is set, a received CR character is
ignored (not read). Otherwise, if ICRNL is set, a received
CR character is translated into a NL character.
Printed 11/19/92 Page 9
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
If IUCLC is set, a received upper case, alphabetic character
is translated into the corresponding lower case character.
If IXON is set, start/stop output control is enabled. A
received STOP character suspends output and a received START
character restarts output. The STOP and START characters
will not be read, but will merely perform flow control func-
tions. If IXANY is set, any input character restarts output
that has been suspended.
If IXOFF is set, the system transmits a STOP character when
the input queue is nearly full, and a START character when
enough input has been read so that the input queue is nearly
empty again.
If IMAXBEL is set, the 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 dis-
turbed. If IMAXBEL is not set, no BEL character is echoed,
and all input present in the input queue is discarded if the
input stream overflows.
The initial input control value is BRKINT, ICRNL, IXON,
ISTRIP.
Output modes
The coflag field specifies the system treatment of output:
OPOST Post-process output.
OLCUC Map lower case to upper on output.
ONLCR Map NL to CR-NL on output.
OCRNL Map CR to NL on output.
ONOCR No CR output at column 0.
ONLRET NL performs CR function.
OFILL Use fill characters for delay.
OFDEL Fill is DEL, else NULL.
NLDLY Select newline delays:
NL0
NL1
CRDLY Select carriage-return delays:
CR0
CR1
CR2
CR3
TABDLY Select horizontal tab delays:
TAB0 or tab expansion:
TAB1
TAB2
TAB3 Expand tabs to spaces.
XTABS Expand tabs to spaces.
BSDLY Select backspace delays:
BS0
Page 10 Printed 11/19/92
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
BS1
VTDLY Select vertical tab delays:
VT0
VT1
FFDLY Select form feed delays:
FF0
FF1
If OPOST is set, output characters are post-processed as
indicated by the remaining flags; otherwise, characters are
transmitted without change.
If OLCUC is set, a lower case alphabetic character is
transmitted as the corresponding upper case character. This
function is often used in conjunction with IUCLC.
If ONLCR is set, the NL character is transmitted as the CR-
NL character pair. If OCRNL is set, the CR character is
transmitted as the NL character. If ONOCR is set, no CR
character is transmitted when at column 0 (first position).
If ONRET is set, the NL character is assumed to do the
carriage-return function; the column pointer is set to 0 and
the delays specified for CR are used. Otherwise, the 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 CR character is actually transmitted.
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 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 OFDEL
is set, the fill character is DEL; otherwise it is NULL.
If a form-feed or vertical-tab delay is specified, it lasts
for about 2 seconds.
Newline delay lasts about 0.10 seconds. If ONLRET is set,
the carriage-return delays are used instead of the newline
delays. If OFILL is set, two fill characters are transmit-
ted.
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 OFILL is set, delay type 1 transmits
two fill characters, and type 2 transmits four fill charac-
ters.
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
Printed 11/19/92 Page 11
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
OFILL is set, two fill characters are transmitted for any
delay.
Backspace delay lasts about 0.05 seconds. If OFILL is set,
one fill character is transmitted.
The actual delays depend on line speed and system load.
The initial output control value is OPOST, ONLCR, TAB3.
Control Modes
The ccflag field describes the hardware control of the ter-
minal:
CBAUD Baud rate:
B0 Hang up
B50 50 baud
B75 75 baud
B110 110 baud
B134 134 baud
B150 150 baud
B200 200 baud
B300 300 baud
B600 600 baud
B1200 1200 baud
B1800 1800 baud
B2400 2400 baud
B4800 4800 baud
B9600 9600 baud
B19200 19200 baud
EXTA External A
B38400 38400 baud
EXTB External B
CSIZE Character size:
CS5 5 bits
CS6 6 bits
CS7 7 bits
CS8 8 bits
CSTOPB Send two stop bits, else one
CREAD Enable receiver
PARENB Parity enable
PARODD Odd parity, else even
HUPCL Hang up on last close
CLOCAL Local line, else dial-up
CIBAUD Input baud rate, if different from output rate
PAREXT Extended parity for mark and space parity
The CBAUD bits specify the baud rate. The zero baud rate,
B0, is used to hang up the connection. If B0 is specified,
the data-terminal-ready signal is not asserted. Normally,
Page 12 Printed 11/19/92
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
this disconnects the line. If the CIBAUD bits are not zero,
they specify the input baud rate, with the CBAUD bits speci-
fying the output baud rate; otherwise, the output and input
baud rates are both specified by the CBAUD bits. The values
for the CIBAUD bits are the same as the values for the CBAUD
bits, shifted left IBSHIFT bits. For any particular
hardware, impossible speed changes are ignored.
The CSIZE bits specify the character size in bits for both
transmission and reception. This size does not include the
parity bit, if any. If CSTOPB is set, two stop bits are
used; otherwise, one stop bit is used. For example, at 110
baud, two stops bits are required.
If PARENB is set, parity generation and detection is
enabled, and a parity bit is added to each character. If
parity is enabled, the PARODD flag specifies odd parity if
set; otherwise, even parity is used.
If CREAD is set, the receiver is enabled. Otherwise, no
characters are received.
If HUPCL is set, the line is disconnected when the last pro-
cess with the line open closes it or terminates. That is,
the data-terminal-ready signal is not asserted.
If CLOCAL is set, the line is assumed to be a local, direct
connection with no modem control; otherwise, modem control
is assumed.
The initial hardware control value after open is B300, CS8,
CREAD, HUPCL.
Local modes
The clflag field of the argument structure is used by the
line discipline to control terminal functions. The basic
line discipline provides the following:
ISIG Enable signals.
ICANON Canonical input (erase and kill processing).
XCASE Canonical upper/lower presentation.
ECHO Enable echo.
ECHOE Echo erase character as BS-SP-BS.
ECHOK Echo NL after kill character.
ECHONL Echo NL.
NOFLSH Disable flush after interrupt or quit.
TOSTOP Send SIGTTOU for background output.
ECHOCTL Echo control characters as ^char, delete as ^?.
ECHOPRT Echo erase character as character erased.
ECHOKE BS-SP-BS erase entire line on line kill.
FLUSHO Output is being flushed.
PENDIN Retype pending input at next read or input character.
Printed 11/19/92 Page 13
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
IEXTEN Enable extended (implementation-defined) functions.
If ISIG is set, each input character is checked against the
special control characters INTR, QUIT, SWTCH, SUSP, STATUS,
and DSUSP. If an input character matches one of these con-
trol characters, the function associated with that character
is performed. If ISIG is not set, no checking is done.
Thus, these special input functions are possible only if
ISIG is set.
If 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 NL, EOF, EOL,
and EOL2. If ICANON is not set, read requests are satisfied
directly from the input queue. A read is not satisfied
until at least MIN characters have been received or the
timeout value 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.
If XCASE is set, and if ICANON is set, an upper case letter
is accepted on input by preceding it with a \ character, and
is output preceded by a \ character. In this mode, the fol-
lowing escape sequences are generated on output and accepted
on input:
for: use:
` \'
| \!
~ \^
{ \(
} \)
\ \\
For example, A is input as \a, \n as \\n, and \N as \\\n.
If ECHO is set, characters are echoed as received.
When ICANON is set, the following echo functions are possi-
ble.
1. If ECHO and ECHOE are set, and ECHOPRT is not set, the
ERASE and WERASE characters are echoed as one or more
ASCII BS SP BS, which clears the last character(s) from
a CRT screen.
2. If ECHO and ECHOPRT are set, the first ERASE and WERASE
character in a sequence echoes as a backslash (\), fol-
lowed by the characters being erased. Subsequent ERASE
and WERASE characters echo the characters being erased,
in reverse order. The next non-erase character causes
Page 14 Printed 11/19/92
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
a slash (/) to be typed before it is echoed. ECHOPRT
should be used for hard copy terminals.
3. If ECHOKE is set, the kill character is echoed by eras-
ing each character on the line from the screen (using
the mechanism selected by ECHOE and ECHOPRT).
4. If ECHOK is set, and ECHOKE is not set, the NL charac-
ter is echoed after the kill character to emphasize
that the line is deleted. Note that an escape charac-
ter (\) or an LNEXT character preceding the erase or
kill character removes any special function.
5. If ECHONL is set, the NL character is echoed even if
ECHO is not set. This is useful for terminals set to
local echo (so called half-duplex).
If ECHOCTL is set, all control characters (characters with
codes between 0 and 37 octal) other than ASCII TAB, ASCII
NL, the START character, and the STOP character, ASCII CR,
and ASCII BS are echoed as ^X, where X is the character
given by adding 100 octal to the code of the control charac-
ter (so that the character with octal code 1 is echoed as
^A), and the ASCII DEL character, with code 177 octal, is
echoed as ^?.
If NOFLSH is set, the normal flush of the input and output
queues associated with the INTR, QUIT, and SUSP characters
is not done. This bit should be set when restarting system
calls that read from or write to a terminal [see sigac-
tion(2)].
If TOSTOP is set, the signal 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 SIGTTOU
signals are excepted and allowed to produce output, if any.
If FLUSHO is set, data written to the terminal is discarded.
This bit is set when the FLUSH character is typed. A pro-
gram can cancel the effect of typing the FLUSH character by
clearing FLUSHO.
If PENDIN is set, any input that has not yet been read is
reprinted when the next character arrives as input.
If IEXTEN is set, the following implementation-defined func-
tions are enabled: special characters (WERASE, REPRINT, DIS-
CARD, and LNEXT) and local flags (TOSTOP, ECHOCTL, ECHOPRT,
ECHOKE, FLUSHO, and PENDIN).
Printed 11/19/92 Page 15
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
The initial line-discipline control value is ISIG, ICANON,
ECHO, ECHOK.
Minimum and Timeout
The MIN and TIME values are described above under Non-
canonical mode input processing. The initial value of MIN
is 1, and the initial value of TIME is 0.
Terminal size
The number of lines and columns on the terminal's display is
specified in the winsize structure defined by
<sys/termios.h> and includes the following members:
unsigned short wsrow; /* rows, in characters */
unsigned short wscol; /* columns, in characters */
unsigned short wsxpixel;/* horizontal size, in pixels */
unsigned short wsypixel;/* vertical size, in pixels */
Termio structure
The System V termio structure is used by some ioctls; it is
defined by <sys/termio.h> and includes the following
members:
unsigned short ciflag;/* input modes */
unsigned short coflag;/* output modes */
unsigned short ccflag;/* control modes */
unsigned short clflag;/* local modes */
char cline; /* line discipline */
unsigned char ccc[NCC];/* control chars */
The special control characters are defined by the array
ccc. The symbolic name NCC is the size of the control-
character array and is also defined by <termio.h>. The
relative positions, subscript names, and typical default
values for each function are as follows:
0 VINTR DEL
1 VQUIT FS
2 VERASE #
3 VKILL @
4 VEOF EOT
5 VEOL NUL
6 VEOL2 NUL
7 reserved
The calls that use the termio structure only affect the
flags and control characters that can be stored in the ter-
mio structure; all other flags and control characters are
unaffected.
Modem lines
On special files representing serial ports, the modem
Page 16 Printed 11/19/92
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
control lines supported by the hardware can be read, and the
modem status lines supported by the hardware can be changed.
The following modem control and status lines may be sup-
ported by a device; they are defined by <sys/termios.h>:
TIOCMLE line enable
TIOCMDTR data terminal ready
TIOCMRTS request to send
TIOCMST secondary transmit
TIOCMSR secondary receive
TIOCMCTS clear to send
TIOCMCAR carrier detect
TIOCMRNG ring
TIOCMDSR data set ready
TIOCMCD is a synonym for TIOCMCAR, and TIOCMRI is a
synonym for TIOCMRNG. Not all of these are necessarily
supported by any particular device; check the manual page
for the device in question.
IOCTLS
The ioctls supported by devices and STREAMS modules provid-
ing the termios interface are listed below. Some calls may
not be supported by all devices or modules. The functional-
ity provided by these calls is also available through the
preferred function call interface specified on termios(2).
TCGETS The argument is a pointer to a termios struc-
ture. The current terminal parameters are
fetched and stored into that structure.
TCSETS The argument is a pointer to a termios struc-
ture. The current terminal parameters are
set from the values stored in that structure.
The change is immediate.
TCSETSW The argument is a pointer to a termios struc-
ture. 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.
TCSETSF The argument is a pointer to a termios struc-
ture. 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 charac-
ters queued for input are discarded and then
the change occurs.
TCGETA The argument is a pointer to a termio
Printed 11/19/92 Page 17
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
structure. The current terminal parameters
are fetched, and those parameters that can be
stored in a termio structure are stored into
that structure.
TCSETA The argument is a pointer to a termio struc-
ture. Those terminal parameters that can be
stored in a termio structure are set from the
values stored in that structure. The change
is immediate.
TCSETAW The argument is a pointer to a termio struc-
ture. Those terminal parameters that can be
stored in a 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.
TCSETAF The argument is a pointer to a termio struc-
ture. Those terminal parameters that can be
stored in a 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.
TCSBRK The argument is an int value. Wait for the
output to drain. If the argument is 0, then
send a break (zero valued bits for 0.25
seconds).
TCXONC Start/stop control. The argument is an int
value. If the argument is 0, suspend output;
if 1, restart suspended output; if 2, suspend
input; if 3, restart suspended input.
TCFLSH The argument is an int value. If the argu-
ment is 0, flush the input queue; if 1, flush
the output queue; if 2, flush both the input
and output queues.
TIOCGPGRP The argument is a pointer to a pidt. Set
the value of that pidt to the process group
ID of the foreground process group associated
with the terminal. See termios(2) for a
description or TCGETPGRP.
TIOCSPGRP The argument is a pointer to a pidt. Asso-
ciate the process group whose process group
Page 18 Printed 11/19/92
TERMIO(7-SVR4) RISC/os Reference Manual TERMIO(7-SVR4)
ID is specified by the value of that pidt
with the terminal. The new process group
value must be in the range of valid process
group ID values. Otherwise, the error EPERM
is returned. See termios(2) for a descrip-
tion of TCSETPGRP.
TIOCGSID The argument is a pointer to a pidt. The
session ID of the terminal is fetched and
stored in the pidt.
TIOCGWINSZ The argument is a pointer to a winsize struc-
ture. The terminal driver's notion of the
terminal size is stored into that structure.
TIOCSWINSZ The argument is a pointer to a winsize struc-
ture. The terminal driver's notion of the
terminal size is set from the values speci-
fied in that structure. If the new sizes are
different from the old sizes, a SIGWINCH sig-
nal is set to the process group of the termi-
nal.
TIOCMBIS The argument is a pointer to an 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.
TIOCMBIC The argument is a pointer to an 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.
TIOCMGET The argument is a pointer to an int. The
current state of the modem status lines is
fetched and stored in the int pointed to by
the argument.
TIOCMSET The argument is a pointer to an int contain-
ing 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.
FILES
files in or under /dev
SEE ALSO
fork(2), ioctl(2), setsid(2), signal(2), termios(2),
streamio(7).
Printed 11/19/92 Page 19