termio(7) termio(7)
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
communications ports that is hardware-independent. The user
interface to this functionality is via function calls (the
preferred interface) described in termios(3C) or ioctl
commands 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 process
to wait until a connection is established. In practice,
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 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 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 completely
full, which is rare (for example, if the number of characters
in the line discipline buffer exceeds {MAX_CANON} and IMAXBEL
[see below] is not set), or when the user has accumulated
{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.
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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.
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. These are process groups which do
not have a member with a parent in another process group that
is in the same session and therefore 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 process 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
c_lflag field, 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 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 (for example, TCSETA, TCSETAW,
TCSETAF, or TIOCSPGRP), its process group will be sent a
SIGTTOU signal, which will normally cause the members of that
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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 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 #) 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 program 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
characters 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.
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termio(7) termio(7)
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). TIME is a timer of
0.10-second granularity that is used to timeout bursty and
short-term data transmissions. The values for MIN and TIME
should be set by the programmer in the termios or termio
structure. 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 character is
received. The interaction between MIN and TIME is as
follows: as soon as one character is received, the
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 re-
activated 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 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
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termio(7) termio(7)
indefinitely waiting for a character; if no character 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
characters 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 interactions 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.
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 (for example, 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 program
does a read of 20 bytes, MIN is 10, and 25 characters are
present, then 20 characters will be returned to the user.
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termio(7) termio(7)
Writing Characters
When one or more characters are written, they are transmitted
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 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.
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 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 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 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
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termio(7) termio(7)
to the program, without waiting for a newline, and
the EOF is discarded. Thus, if no characters are
waiting (that is, the EOF occurred at the beginning
of a line) zero characters are passed back, which is
the standard end-of-file indication. The EOF
character is not echoed unless it is escaped or
ECHOCTL is set. 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 cannot
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
process 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 process
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 output
temporarily. It is useful with CRT terminals to
prevent output from disappearing before it can be
read. While output is suspended, STOP characters
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.
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termio(7) termio(7)
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 otherwise
be interpreted by the system (for example, 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
arrangements 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 terminal
is closed.
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.
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:
tcflag_t c_iflag; /* input modes */
tcflag_t c_oflag; /* output modes */
tcflag_t c_cflag; /* control modes */
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termio(7) termio(7)
tcflag_t c_lflag; /* local modes */
cc_t c_cc[NCCS]; /* control chars */
The special control characters are defined by the array c_cc.
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 VERASE #
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 VWERASE ETB
15 VLNEXT SYN
16-19 reserved
For the non-canonical mode the positions of VEOF and VEOL are
shared by VMIN and VTIME:
4 VMIN used to set the value of MIN
5 VTIME used to set the value of TIME
Input Modes
The c_iflag field describes the basic terminal input control:
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.
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.
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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 framing
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
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.
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.
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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 functions.
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 disturbed.
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 c_oflag 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:
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TAB1
TAB2
TAB3 Expand tabs to spaces.
XTABS Expand tabs to spaces.
BSDLY Select backspace delays:
BS0
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.
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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 transmitted.
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
characters.
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 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 c_cflag field describes the hardware control of the
terminal:
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:
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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, this
disconnects the line. If the CIBAUD bits are not zero, they
specify the input baud rate, with the CBAUD bits specifying
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
process 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.
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The initial hardware control value after open is B300, CS8,
CREAD, HUPCL.
Local Modes
The c_lflag 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.
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 control
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 following
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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 possible.
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 (\), followed
by the characters being erased. Subsequent ERASE and WERASE
characters echo the characters being erased, in reverse
order. The next non-erase character causes 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 erasing
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 character is
echoed after the kill character to emphasize that the line
is deleted. Note that an escape character (\) 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
Copyright 1994 Novell, Inc. Page 16
termio(7) termio(7)
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 character (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 sigaction(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 program
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
functions are enabled: special characters (WERASE, REPRINT,
DISCARD, and LNEXT) and local flags (TOSTOP, ECHOCTL, ECHOPRT,
ECHOKE, FLUSHO, and PENDIN).
The initial line-discipline control value is ISIG, ICANON,
ECHO, ECHOK.
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:
Copyright 1994 Novell, Inc. Page 17
termio(7) termio(7)
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 */
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 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 */
The special control characters are defined by the array c_cc.
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
For the non-canonical mode the positions of VEOF and VEOL are
shared by VMIN and VTIME:
4 VMIN used to set the value of MIN
5 VTIME used to set the value of TIME
The calls that use the termio structure only affect the flags
and control characters that can be stored in the termio
structure; all other flags and control characters are
unaffected.
Modem lines
On special files representing serial ports, the modem 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 supported by a
device; they are defined by sys/termios.h:
Copyright 1994 Novell, Inc. Page 18
termio(7) termio(7)
TIOCM_LE line enable
TIOCM_DTR data terminal ready
TIOCM_RTS request to send
TIOCM_ST secondary transmit
TIOCM_SR secondary receive
TIOCM_CTS clear to send
TIOCM_CAR carrier detect
TIOCM_RNG ring
TIOCM_DSR data set ready
TIOCM_CD is a synonym for TIOCM_CAR, and TIOCM_RI is a synonym
for TIOCM_RNG. 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 providing
the termios 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 termios(3C).
TCGETS The argument is a pointer to a termios
structure. The current terminal parameters are
fetched and stored into that structure.
TCSETS The argument is a pointer to a termios
structure. 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
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.
TCSETSF The argument is a pointer to a 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.
Copyright 1994 Novell, Inc. Page 19
termio(7) termio(7)
TCGETA The argument is a pointer to a termio
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
structure. 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
structure. 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
structure. 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 argument
is 0, flush the input queue; if 1, flush the
output queue; if 2, flush both the input and
output queues. On some controllers, if the
argument is 0, input flow control characters
will be flushed, causing the unflushed output
Copyright 1994 Novell, Inc. Page 20
termio(7) termio(7)
queue to overflow a busy output device.
TIOCGPGRP The argument is a pointer to a pid_t. Set the
value of that pid_t to the process group ID of
the foreground process group associated with
the terminal. See termios(3C) for a
description or TCGETPGRP.
TIOCSPGRP The argument is a pointer to a pid_t.
Associate the process group whose process group
ID is specified by the value of that pid_t 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(3C) for a description of
TCSETPGRP.
TIOCGSID The argument is a pointer to a pid_t. The
session ID of the terminal is fetched and
stored in the pid_t.
TIOCGWINSZ The argument is a pointer to a winsize
structure. The terminal driver's notion of the
terminal size is stored into that structure.
TIOCSWINSZ The argument is a pointer to a 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 SIGWINCH signal
is set to the process group of the terminal.
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.
Copyright 1994 Novell, Inc. Page 21
termio(7) termio(7)
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 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.
FILES
/dev/*
REFERENCES
fork(2), ioctl(2), setsid(2), signal(2), streamio(7),
termios(3C)
Copyright 1994 Novell, Inc. Page 22