termio(7) Miscellaneous Information Manual termio(7)
NAME
termio, termios - general terminal interface
DESCRIPTION
All HP-UX asynchronous communications ports use the same general interface, regardless of what hardware is involved. Network connections
such as (see rlogin(1) use the pseudo-terminal interface (see pty(7).
This discussion centers around the common features of this interface.
Opening a Terminal File
When a terminal file is opened, it normally causes the process to wait until a connection is established. In practice, users' programs
seldom open these files; they are opened by special programs such as (see getty(1M)) and become a user's standard input, standard output,
and standard error files.
If both the and flags (see open(2)) are clear, an open blocks until the type of modem connection requested (see modem(7)) is completed. If
either the or flag is set, an open succeeds and return immediately without waiting for the requested modem connection to complete. The
flag (see can also affect open(2).
Process Groups
A terminal can have a foreground process group associated with it. This foreground process group plays a special role in handling signal-
generating input characters.
Command interpreter processes can allocate the terminal to different jobs (process groups) by placing related processes in a single process
group and associating this process group with the terminal. A terminal's foreground process group can be set or examined by a process,
assuming that the permission requirements are met (see tcsetpgrp(3C) or tcgetpgrp(3C)). The terminal interface aids in this allocation by
restricting access to the terminal by processes that are not in the foreground process group.
A process group is considered orphaned when the parent of every member of the process group is either itself a member of the process group
or is not a member of the group's session (see Sessions).
Sessions
A process that creates a session (see setsid(2) or setpgrp(2)) becomes a session leader. Every process group belongs to exactly one ses-
sion. A process is considered to be a member of the session of which its process group is a member. A newly created process joins the
session of its parent. A process can change its session membership (see setpgid(2) or setpgrp(2)). Usually a session comprises all the
processes (including children) created as a result of a single login.
The Controlling Terminal
A terminal can belong to a process as its controlling terminal. Each process of a session that has a controlling terminal has the same
controlling terminal. A terminal can be the controlling terminal for at most one session. The controlling terminal for a session is allo-
cated by the session leader. If a session leader has no controlling terminal and opens a terminal device file that is not already associ-
ated with a session without using the option (see open(2), the terminal becomes the controlling terminal of the session and the controlling
terminal's foreground process group is set to the process group of the session leader. While a controlling terminal is associated with a
session, the session leader is said to be the controlling process of the controlling terminal.
The controlling terminal is inherited by a child process during a (see fork(2)). A process relinquishes its controlling terminal if it
creates a new session with or (see setsid(2) and setpgrp(2)), or when all file descriptors associated with the controlling terminal have
been closed.
When the controlling process terminates, the controlling terminal is disassociated from the current session, allowing it to be acquired by
a new session leader. A signal is sent to all processes in the foreground process group of the controlling terminal. Subsequent access to
the terminal by other processes in the earlier session can be denied (see with attempts to access the terminal treated as if a modem dis-
connect had been sensed.
Terminal Access Control
Read operations are allowed (see from processes in the foreground process group of their controlling terminal. If a process is not in the
foreground process group of its controlling terminal, the process and all member's of its process group are considered to be in a back-
ground process group of this controlling terminal. All attempts by a process in a background process group to read from its controlling
terminal will be denied. If denied and the reading process is ignoring or blocking the signal, or the process (on systems that implement
vfork separately from fork) has made a call to vfork(2) but has not yet made a call to exec(2), or the process group of the reading process
is orphaned, returns -1 with set to and no signal is sent. In all other cases where the read is denied, the process group of the reading
process will be sent a signal. The default action of the signal is to stop the process to which it is sent.
If the process is in the foreground process group of its controlling terminal, write operations are allowed (see Attempts by a process in a
background process group to write to its controlling terminal are denied if (see is set, the process is not ignoring and not blocking the
signal, and the process (on systems that implement vfork separately from fork) has not made a call to vfork(2) without making a subsequent
call to exec(2). If the write is denied and the background process group is orphaned, the returns -1 with set to If the write is denied
and the background process group is not orphaned, the signal is sent to the process group of the writing process. The default action of
the signal is to stop the process to which it is sent.
Certain calls that set terminal parameters are treated in the same fashion as write, except that is ignored; that is, the effect is identi-
cal to that of terminal writes when is set.
Input Processing and Reading Data
A terminal device associated with a terminal device file can operate in full-duplex mode, so that data can arrive, even while data output
is occurring. Each terminal device file has an input queue associated with it into which incoming data is stored by the system before
being read by a process. The system imposes a limit, on the number of characters that can be stored in the input queue. This limit is
dependent on the particular implementation, but is at least 256. When the input limit is reached, all saved characters are discarded with-
out notice.
All input is processed either in canonical mode or non-canonical mode (see Canonical Mode Input Processing and Additionally, input charac-
ters are processed according to the (see and (see fields. For example, such processing can include echoing, which in general means trans-
mitting input characters immediately back to the terminal when they are received from the terminal. This is useful for terminals that
operate in full-duplex mode.
The manner in which data is provided to a process reading from a terminal device file depends on whether the terminal device file is in
canonical or non-canonical mode.
Another dependency is whether the or flag is set by either open(2) or fcntl(2). If the and flags are both clear, the read request is
blocked until data is available or a signal is received. If either the or flag is set, the read request completes without blocking in one
of three ways:
o If there is enough data available to satisfy the entire request, completes successfully, having read all of the data requested, and
returns the number of characters read.
o If there is not enough data available to satisfy the entire request, completes successfully, having read as much data as possible, and
returns the number of characters read.
o If there is no data available, returns -1, with set to when the flag is set. Otherwise, (flag is clear and is set) completes success-
fully, having read no data, and returns a count of 0.
The availability of data depends upon whether the input processing mode is canonical or non-canonical. The following sections, and
describe each of these input processing modes. In canonical mode input processing, terminal input is processed in units of lines, where a
line is delimited by a new-line (NL) character, an end-of-file (EOF) character, or an end-of-line character (EOL) or (EOL2). See Special
Characters for more information on and This means that a read request does not return until an entire line has been typed or a signal has
been received. Also, no matter how many characters are requested in the read call, at most one line will be returned. It is not, however,
necessary to read a whole line at once; any number of characters can be requested in a read, even one, without losing information.
is the limit on the number of characters in a line. This limit varies with each particular implementation, but is at least 256.
When the limit is reached, all characters in the current undelimited line are discarded without notice.
Erase and kill processing occur when any of three special characters, the ERASE, WERASE, or KILL characters (see is received. This pro-
cessing affects data in the input queue that has not yet been delimited by a NL, EOF, EOL, or EOL2 character. This undelimited data makes
up the current line. The ERASE character deletes the last character in the current line, if one exists. The WERASE character deletes the
last word in the current line, if one exists. A word is defined as a series of non-blank characters (tabs are equivalent to blanks). The
KILL character deletes all data in the current line, if any, and optionally outputs a new-line (NL) character. These characters operate on
a key-stroke basis, independent of any backspacing or tabbing that may have preceded them. ERASE, WERASE, and KILL characters have no
effect if the current line is empty. ERASE, WERASE, and KILL characters are not placed in the input queue. In non-canonical mode input
processing, input characters are not assembled into lines, and erase and kill processing does not occur. The values of the and members of
the array (see are used to determine how to process the characters received. represents the minimum number of characters that should be
received before successfully returns. TIME is a timer of 0.10 second granularity that is used to timeout bursty and short term data trans-
missions. The four possible cases for MIN and TIME and their interactions are described below.
Case A: MIN > 0, TIME > 0
In this case, TIME serves as an inter-character timer and is activated after the first character is received. Since it is an inter-charac-
ter timer, it is reset after each character is received. The interaction between MIN and TIME is as follows:
o As soon as one character is received, the inter-character timer is started.
o If MIN characters are received before the inter-character timer expires (remember that the timer is reset upon receipt of each charac-
ter), the read is satisfied. If the timer expires before MIN characters are received, the characters received to that point are
returned to the user.
o 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 blocks until the MIN and TIME mechanisms are activated by the receipt of
the first character, or a signal is received.
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 after any previous read completes (that is, the pending read blocks until MIN characters are received), or a
signal is received. A program that uses this case to handle record-based terminal I/O can block indefinitely in the read operation.
Case C: MIN = 0, TIME > 0
In this case, since the value of MIN is zero, TIME no longer represents an inter-character timer. It now serves as a read timer that is
activated as soon as the function is processed. A read is satisfied as soon as a single character is received or the read timer expires.
If the timer expires, no character is returned. If the timer does not expire, the only way the read can be satisfied is by a character
being received. A read cannot block indefinitely waiting for a character because if no character is received within TIME x 0.10 seconds
after the read is initiated, returns a value of zero, having read no data.
Case D: MIN = 0, TIME = 0
The number of characters requested or the number of characters currently available, whichever is less, is returned without waiting for more
characters to be input. If no characters are available, returns a value of zero, having read no data.
Some points to note about MIN and TIME:
1. In the above explanations, 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 inter-character timer while in case C ( MIN = 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
(such as file transfer programs) where a program would like to process at least MIN characters at a time. In case A, the inter-character
timer is activated by a user as a safety measure while in case B it 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, while 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 initiates a
read of 20 characters when MIN is 10 and 25 characters are present, 20 characters will be returned to the user. Had the program requested
all characters, all 25 characters would be returned to the user.
Furthermore, if TIME is greater than zero and MIN is greater than the read will never terminate as a result of MIN characters being
received because all the saved characters are discarded without notice when is exceeded. If TIME is zero and MIN is greater than the read
will never terminate unless a signal is received.
Special Characters
Certain characters have special functions on input, output, or both. Unless specifically denied, each special character can be changed or
disabled. To disable a character, set its value to (see unistd(5)). These special functions and their default character values are:
INTR (Rubout or ASCII DEL) special character on input and is recognized if (see is enabled. Generates a signal which is sent
to all processes in the foreground process group for which the terminal is the controlling terminal. Normally, each such
process is forced to terminate, but arrangements can be made to either ignore or hold the signal, or to receive a trap to
an agreed-upon location; see signal(2) and signal(5). If is set, the INTR character is discarded when processed. If is
clear, the INTR character is processed as a normal data character, and no signal is sent.
QUIT (Control- or ASCII FS) special character on input. Recognized if (see is set. The treatment of this character is iden-
tical to that of the INTR character except that a signal is generated and the processes that receive this signal are not
only terminated, but a core image file (called is created in the current working directory if the implementation supports
core files.
SWTCH (ASCII NUL) special character on input and is only used by the shell layers facility shl(1). The shell layers facility
is not part of the general terminal interface. No special functions are performed by the general terminal interface when
SWTCH characters are encountered.
ERASE special character on input and is recognized if (see is enabled. Erases the preceding character. Does not erase beyond
the start of a line, as delimited by a NL, EOF, EOL, or EOL2 character. If is enabled, the ERASE character is discarded
when processed. If is not enabled, the ERASE character is treated as a normal data character.
WERASE (disabled) special character on input and is recognized if (see is enabled. Erases the preceding word. Does not erase
beyond the start of a line, as delimited by a NL, EOF, EOL, or EOL2 character. If is enabled, the WERASE character is
discarded when processed. If is not enabled, the WERASE character is treated as a normal data character.
KILL special character on input and is recognized if is enabled. KILL deletes the entire line, as delimited by a NL, EOF,
EOL, or EOL2 character. If is enabled, the KILL character is discarded when processed. If is not enabled, the KILL
character is treated as a normal data character.
EOF (Control-D or ASCII EOT) special character on input and is recognized if is enabled. EOF can 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 there are no characters waiting, (that is, the EOF
occurred at the beginning of a line) a character count of zero is returned from representing an end-of-file indication.
If is enabled, the EOF character is discarded when processed. If is not enabled, the EOF character is treated as a nor-
mal data character.
NL (ASCII LF) special character on input and is recognized if flag is enabled. It is the line delimiter If is not enabled,
the NL character is treated as a normal data character.
EOL (ASCII NUL) special character on input and is recognized if is enabled. EOL is an additional line delimiter similar to
NL. It is not normally used. If is not enabled, the EOL character is treated as a normal data character.
EOL2 (disabled) special character on input and is recognized if is enabled. EOL2 is an additional line delimiter similar to
EOL. It is not normally used. If is not enabled, the EOL2 character is treated as a normal data character.
SUSP (disabled) special character recognized on input. If is enabled, receipt of the SUSP character causes a signal to be
sent to all processes in the foreground process group for which the terminal is the controlling terminal, and the SUSP
character is discarded when processed. If is not enabled, the SUSP character is treated as a normal data character.
Command interpreter processes typically set SUSP to Control-Z.
DSUSP (disabled) special character recognized on input. If is enabled, and a process in the foreground process group attempts
to read the DSUSP character, a signal is sent to all processes in the foreground process group for which the terminal is
the controlling terminal, and the DSUSP character is then discarded. If is not enabled, the DSUSP character is treated
as a normal data character. Note that DSUSP is similar to SUSP except that 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 (Control-S or ASCII DC3) special character on both input and output. If (output control) is enabled, processing of the
STOP character temporarily suspends output to the terminal device. This is useful with CRT terminals to prevent output
from disappearing before it can be read. While output is suspended and is enabled, STOP characters are ignored and not
read. If is enabled, the STOP character is discarded when processed. If is not enabled, the STOP character is treated
as a normal data character. If (input control) is enabled, the system sends a STOP character to the terminal device when
the number of unread characters in the input queue is approaching a system specified limit. This is an attempt to pre-
vent this buffer from overflowing by telling the terminal device to stop sending data.
START (Control-Q or ASCII DC1) special character on both input and output. If (output control) is enabled, processing of the
START character resumes output that has been suspended. While output is not suspended and is enabled, START characters
are ignored and not read. If is enabled, the START character is discarded when processed. If is not enabled, the START
character is treated as a normal data character. If IXOFF (input control) is enabled, the system sends a START character
to the terminal device when the input queue has drained to a certain system-defined level. This occurs when the input
queue is no longer in danger of possibly overflowing.
CR (ASCII CR) special character on input is recognized if is enabled. When and are enabled and is not enabled, this charac-
ter is translated into a NL, and has the same affect as the NL character. If and are enabled, the CR character is
ignored. If is enabled and both and are not enabled, the CR character is treated as a normal data character.
LNEXT (disabled) special character recognized on input. Causes the special meaning of the next character to be ignored. This
works for all special characters specified above. It allows characters to be input that would otherwise be interpreted
by the system for a special function.
The special characters are assigned their default character values when the terminal port is opened. The default values used are those
specified by the System V Interface Definition, Third Edition (SVID3), except for the WERASE (Control-W) and LNEXT (Control-V) characters
which are set to to maintain binary compatibility with previous releases of HP-UX. The default character values assigned when the port is
opened can be changed for all ports on a system wide basis through the use of the command (see stty(1)). The character values may also be
changed for a specific port after it is opened using the command. The NL and CR characters cannot be changed or disabled. The character
values for the remaining special characters can be changed or disabled to suit individual tastes.
If is set (see the ERASE, KILL, and EOF characters can be escaped by a preceding character, in which case no special function is performed.
These characters, and the remaining special characters, may also be escaped by preceding them with the LNEXT character (see LNEXT above).
If two or more special characters have the same value, the function performed when the character is processed is undefined.
Modem Disconnect
If a modem disconnect is detected by the terminal interface for a controlling terminal, and if is clear in the field for the terminal (see
the signal is sent to the controlling process of the controlling terminal. Unless other arrangements have been made, this causes the con-
trolling process to terminate. Any subsequent read from the terminal device returns with an end-of-file indication until the device is
closed. Thus, processes that read a terminal file and test for end-of-file can terminate appropriately after a disconnect. Any subsequent
to the terminal device returns -1, with set to until the device is closed.
Closing a Terminal Device File
The last process to close a terminal device file causes any output not already sent to the device to be sent to the device even if output
was suspended. This last close always blocks (even if non-blocking I/O has been specified) until all output has been sent to the terminal
device. Any input that has been received but not read is discarded.
Writing Data and Output Processing
When characters are written, they are placed on the output queue. Characters on the output queue are transmitted to the terminal as soon
as previously-written characters are sent. These characters are processed according to the field (see Input characters are echoed by
putting them in the output queue as they arrive. If a process produces characters for output more rapidly than they can be sent, the
process is suspended when its output queue exceeds some limit. When the queue has drained down to some threshold, the process is resumed.
termios Structure
Routines that need to control certain terminal I/O characteristics can do so by using the structure as defined in the header file The
structure is defined as follows:
#define NCCS 16
struct termios {
tcflag_t c_iflag; /* input modes */
tcflag_t c_oflag; /* output modes */
tcflag_t c_cflag; /* control modes */
tcflag_t c_lflag; /* local modes */
tcflag_t c_reserved; /* reserved for future use */
cc_t c_cc[NCCS]; /* control chars */
};
The special characters are defined by the array The relative positions and default values for each special character function are as fol-
lows:
INTR VINTR DEL
QUIT VQUIT Control-|
ERASE VERASE #
KILL VKILL @
EOF VEOF Control-D
EOL VEOL NUL
EOL2 VEOL2 disabled
MIN VMIN NUL
TIME VTIME Control-D
SUSP VSUSP disabled
START VSTART Control-Q
STOP VSTOP Control-S
WERASE VWERASE disabled
LNEXT VLNEXT disabled
DSUSP VDSUSP disabled
termio Structure
The structure has been superseded by the structure and is provided for backward compatibility with prior applications (see The structure is
defined in the header file and is defined as follows:
#define NCC 8
struct termio {
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 */
};
Modes
The next four sections describe the specific terminal characteristics that can be set using the and structures (see Any bits in the modes
fields that are not explicitly defined below are ignored. However, they should always be clear to prevent future compatibility problems.
Input Modes
The field describes the basic terminal input control:
Ignore break condition.
Signal interrupt on break.
Ignore characters with parity errors.
Mark parity errors.
Enable input parity check.
Strip character.
Map NL to CR on input.
Ignore CR.
Map CR to NL on input.
Map uppercase to lowercase on input.
Enable start/stop output control.
Enable any character to restart output.
Enable start/stop input control.
Enable BEL on input line too long.
A break condition is defined as a sequence of zero-value bits that continues for more than the time to send one character. For example, a
character framing or parity error with data all zeros is interpreted as a single break condition.
If is set, the break condition is ignored. Therefore the break condition cannot be read by any process. If is clear and is set, the break
condition flushes both the input and output queues and, if the terminal is the controlling terminal of a foreground process group, the
break condition generates a single signal to that foreground process group. If neither nor is set, a break condition is read as a single
character, or if is set, as the three-character sequence
If is set, characters with other framing and parity errors (other than break) are ignored.
If is set, and is clear, a character with a framing or parity error (other than break) is read as the three-character sequence: X, where X
is the data of the character received in error. To avoid ambiguity in this case, if is clear, a valid character of is read as If both and
are clear, a framing or parity error (other than break) is read as the character
If is set, input parity checking is enabled. If is clear, input parity checking is disabled. Whether input parity checking is enabled or
disabled is independent of whether parity detection is enabled or disabled (see If is set (see and is clear, parity generation is enabled
but input parity checking is disabled; the hardware to which the terminal is connected will recognize the parity bit, but the terminal spe-
cial file will not check whether this bit is set correctly or not.
The following table shows the interrelationship between the flags and The column marked Input gives various types of input characters
received, indicated as follows:
NUL character
Character other than
NUL
Parity error detected
Framing error detected
Items enclosed in brackets indicate one or more of the conditions are true.
If the flag is clear, characters received with parity errors are not processed according to this table, but instead, as if no parity error
had occurred. Under the flag columns, indicates the flag is set, indicates the flag is not set, and indicates the flag may be set or
clear. The column labeled shows the results that will be passed to the application code. A -- indicates that no character or condition is
passed to the application code. The value indicates that no character is returned, but that the signal is sent to the foreground process
group of the controlling terminal.
Input 1IGNBRK BRKINT IGNPAR PARMRK Read
----------------------------------------------------------------
0[PF] Set X X X --
0[PF] Clear Set X X SIGINT
0[PF] Clear Clear X Set '377',' ',' '
0[PF] Clear Clear X Clear ' '
C[PF] X X Set X --
C[PF] X X Clear Set '377',' ',C
C[PF] X X Clear Clear ' '
'377' X X X Set '377','377'
If is set, valid input characters are first stripped to 7-bits, otherwise all 8-bits are processed.
If is set, a received NL character is translated into a CR character. If is set, a received CR character is ignored (not read). If is
clear and is set, a received CR character is translated into a NL character.
If is set, a received uppercase alphabetic character is translated into the corresponding lowercase character.
If is set, start/stop output control is enabled. A received STOP character suspends output and a received START character restarts output.
If and are set, any input character without a framing or parity error restarts output that has been suspended. When these three flags are
set, output suspended, and an input character received with a framing or parity error, output resumes if processing it results in data
being read. When is set, START and STOP characters are not read, but merely perform flow control functions. When is clear, the START and
STOP characters are read.
If is set, start/stop input control is enabled. The system transmits a STOP character when the number of characters in the input queue
exceeds a system defined value (high water mark). This is intended to cause the terminal device to stop transmitting data in order to pre-
vent the number of characters in the input queue from exceeding When enough characters have been read from the input queue that the number
of characters remaining is less than another system defined value (low water mark), the system transmits a START character which is
intended to cause the terminal device to resume transmitting data (without risk of overflowing the input queue). In order to avoid poten-
tial deadlock, is ignored in canonical mode whenever there is no line delimiter in the input buffer. In this case, the STOP character is
not sent at the high water mark, but will be transmitted later if a delimiter is received. If all complete lines are read from the input
queue leaving only a partial line with no line delimiter, the START character is sent, even if the number of characters is still greater
than the low water mark. When is set and the input stream contains more characters between line delimiters than the high water mark
allows, there is no guarantee that can prevent buffer overflow and data loss, because the STOP character may not be sent in time, if at
all.
If is set, the ASCII BEL character is echoed if the input queue overflows. Further input is not stored, but any input present in the input
queue is not discarded. If is clear, no ASCII BEL character is echoed, and the input already present in the input queue is discarded when
the input queue overflows.
The initial input control value is all bits clear.
Output Modes
The field specifies the system treatment of output:
Postprocess output.
Map lowercase to uppercase on output.
Map NL to CR-NL on output.
Map CR to NL on output.
No CR output at column 0.
NL performs CR function.
Use fill characters for delay.
Fill is DEL, else NUL.
Select new-line delays:
No delay
Delay type 1
Select carriage-return delays:
No delay
Delay type 1
Delay type 2
Delay type 3
Select horizontal-tab delays:
No delay
Delay type 1
Delay type 2
Expand tabs to spaces.
Expand tabs to spaces.
Select backspace delays:
No delay
Delay type 1
Select vertical-tab delays:
No delay
Delay type 1
Select form-feed delays:
No delay
Delay type 1
If is set, output characters are post-processed as indicated by the remaining flags; otherwise characters are transmitted without change.
If is set, a lowercase alphabetic character is transmitted as the corresponding uppercase character. This function is often used in con-
junction with
If is set, the NL character is transmitted as the CR-NL character pair. If is set, the CR character is transmitted as the NL character.
If is set, no CR character is transmitted when at column 0 (first position). If is set, the NL character is assumed to do the carriage-
return function; the column pointer will be set to 0, and the delays specified for CR will be used. If is clear, the NL character is
assumed to perform only the line-feed function; the delays specified for NL are used and the column pointer remains unchanged. For all of
these cases, the column pointer is always 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 termi-
nal. The values of and FF0 indicate no delay. If 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 is set, the fill character is DEL; otherwise NUL.
If a form-feed or vertical-tab delay is specified, it lasts for about 2 seconds.
New-line delay lasts about 0.10 seconds. If is set, carriage-return delays are used instead of the new-line delays. If is set, two fill
characters are transmitted.
Carriage-return delay type 1 depends on the current column position; type 2 is about 0.10 seconds; type 3 about 0.15 seconds. If is set,
delay type 1 transmits two fill characters; type 2, four fill characters.
Horizontal-tab delay type 1 is depends on the current column position. Type 2 is about 0.10 seconds; type 3 specifies that tabs are to be
expanded into spaces. If is set, two fill characters are transmitted for any delay.
Backspace delay lasts about 0.05 seconds. If is set, one fill character is transmitted.
The actual delays depend on line speed and system load.
The initial output control value is all bits clear.
Control Modes
The field describes the hardware control of the terminal:
CBAUD Baud rate: CSIZE Character size:
B0 Hang up CS5 5 bits
B50 50 baud CS6 6 bits
B75 75 baud CS7 7 bits
B110 110 baud CS8 8 bits
B134 134.5 baud
B150 150 baud CSTOPB Send two stop bits, else one.
B200 200 baud CREAD Enable receiver.
B300 300 baud PARENB Parity enable.
B600 600 baud PARODD Odd parity, else even.
B900 900 baud HUPCL Hang up on last close.
B1200 1200 baud CLOCAL Local line, else dial-up.
B1800 1800 baud LOBLK Reserved for use by shl(1).
B2400 2400 baud
B3600 3600 baud
B4800 4800 baud
B7200 7200 baud
B9600 9600 baud
B19200 19200 baud
B38400 38400 baud
EXTA External A
EXTB External B
The CBAUD bits specify the baud rate. The zero baud rate, is used to hang up the connection. If is specified, the modem control lines
(see modem(7)) cease to be asserted. Normally, this disconnects the line. For any particular hardware, impossible speed changes are
ignored. is provided for use with the structure. When the structure is used, several routines are available for setting and getting the
input and output baud rates (see
The bits specify the character size in bits for both transmission and reception. This size does not include the parity bit, if any. If is
set, two stop bits are used; otherwise one stop bit. For example, at 110 baud, many devices require two stop bits.
If is set, parity generation is enabled (a parity bit is added to each output character). Furthermore, parity detection is enabled (incom-
ing characters are checked for the correct parity). If is set, specifies odd parity if set; otherwise even parity is used. If is clear,
both parity generation and parity checking are disabled.
If is set, the receiver is enabled. Otherwise no characters can be received.
The specific effects of the and bits depend on the mode and type of the modem control in effect. See modem(7) for the details.
If is set, the modem control lines for the port are lowered (disconnected) when the last process using the open port closes it or termi-
nates.
If is set, a connection does not depend on the state of the modem status lines. If is clear, the modem status lines are monitored.
Under normal circumstances, a call to waits for a modem connection to complete. However, if either the or the flags are set or is set, the
returns immediately without waiting for the connection. If is set, see for the effects of and for those files for which the connection has
not been established or has been lost.
is used by the shell layers facility (see shl(1)). The shell layers facility is not part of the general terminal interface, and the bit is
not examined by the general terminal interface.
The initial hardware control value after open is and
Local Modes
The field is used to control terminal functions.
Enable signals.
Canonical input (erase and kill processing).
Canonical upper/lower presentation.
Enable echo.
Echo ERASE as correcting backspace sequence.
Echo NL after kill character.
Echo NL.
Disable flush after interrupt, quit, or suspend.
Send SIGTTOU for background output.
Echo control characters as ^char,
DEL as ^?.
Echo erased character as character is erased.
BS SP BS erase entire line on line kill.
Output is being flushed.
Reprocess pending input at next read or input character.
Enable extended functions.
If is set, each input character is checked against the special control characters INTR, QUIT, SUSP, and DSUSP (see If an input character
matches one of these control characters, the function associated with that character is performed and the character is discarded. If is
clear, no checking is done and the character is treated as a normal data character. Thus these special input functions are possible only
if is set.
If 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, or EOL2. If is clear, read requests are satisfied directly from the input queue. A read blocks until at
least MIN characters have been received or the timeout value TIME has expired between characters. (See This allows fast bursts of input to
be read efficiently while still allowing single-character input. The time value represents tenths of seconds.
If is set, and if is set, an uppercase letter is accepted on input by preceding it with a character, and is output preceded by a character.
In this mode, the following escape sequences are generated on output and accepted on input:
To obtain: Use:
` '
| !
{ (
} )
\
For example, is input as as and as would normally be used in conjunction with and for terminals that support only the first-sixty-four-
character limited character set. In this case, processing is done before for input, and processing is done after for output. Therefore
typing causes an to be read because of and typing causes an to be read since produces which is turned into by the processing.
If is set, characters are echoed back to the terminal when received. If is clear, characters are not echoed.
When 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 as described in Furthermore, the following echo functions are possible.
If and are set, the ERASE and WERASE characters are echoed as the three-character ASCII sequence BS SP BS, which clears the last character
or word from the CRT screen.
If and are set, and is clear, the first ERASE and WERASE character in a sequence echoes a backslash () followed by the characters being
erased. Subsequent ERASE or 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.
If and are set, the KILL character is echoed by erasing each character on the line from the CRT screen using using the method selected by
and
If and are set, all control characters (characters with codes between 0 and 37 octal) other than ASCII TAB, ASCII NL, the START and STOP
characters, ASCII CR, and ASCII BS are echoed as ^char, where char is the character given by adding 100 octal to the control character's
code.
If is set and is not set, the NL character is echoed after the kill character to emphasize that the line is being deleted.
If is set, the NL character is echoed even if is clear. This is useful for terminals set to local echo (that is, half duplex).
Unless escaped, the EOF character is not echoed. Because ASCII EOT is the default EOF character, this prevents terminals that respond to
EOT from hanging up.
If is set, the normal flush of the input and output queues associated with quit, interrupt, and suspend characters is not done. However,
does not affect the flushing of data upon receipt of a break when is set.
If the bit is set, an attempt by a process that is not in the foreground process group to write to its controlling terminal will be denied
when the process is not ignoring and not blocking the signal. If the write is denied and the process is a member of an orphaned process
group returns -1 and sets to and no signal is sent. If the write is denied and the process is a not a member of an orphaned process group,
the signal is sent to that process group.
If is set, data written to the terminal device is discarded. This bit is set by a program. A program can cancel the effect by clearing
If is set, any input that has not been read is reprocessed and possibly re-echoed when the next character arrives as input.
If is set, the ERASE, KILL, and EOF characters can be escaped by a preceding character, in which case no special function is done.
must be set before the and functions are allowed. In addition, the special characters WERASE and LNEXT are allowed only if is set. does
not affect any other functions.
The initial local control value is all-bits-clear.
Special Control Characters
Special control characters are defined in the array All of these special characters can be changed. The subscript name and description for
each element in both canonical and non-canonical mode are shown in the following table.
Subscript Usage
Canonical Non-Canonical Description
-----------------------------------------------
VEOF EOF character
VEOL EOL character
VEOL2 EOL2 character
VERASE ERASE character
VWERASE WERASE character
VINTR VINTR INTR character
VKILL KILL character
VMIN MIN value
VQUIT VQUIT QUIT character
VSTART VSTART START character
VSTOP VSTOP STOP character
VSUSP VSUSP SUSP character
VDSUSP VDSUSP DSUSP character
VTIME TIME value
VLNEXT VLNEXT LNEXT character
termios Structure-Related Functions
The following functions are provided when using the termios structure. Note that the effects on the terminal device of the and functions
do not become effective until the function is successfully called. Refer to the appropriate manual entries for details.
termios Structure Functions
Function Description
---------------------------------------
cfgetospeed() get output baud rate
cfgetispeed() get input baud rate
cfsetospeed() set output baud rate
cfsetispeed() set input baud rate
tcgetattr() get terminal state
tcsetattr() set terminal state
termio Structure-Related OCTL Commands
Several system calls apply to terminal files that use the structure (see If a requested command is not recognized, the request returns -1
with set to
system calls that reference the structure have the form:
Commands using this form are:
Get the parameters associated with the terminal
and store them in the structure referenced by arg. This command is allowed from a background process; however, the
information may be subsequently changed by a foreground process.
Set the parameters associated with the terminal from the
structure referenced by arg. The change is immediate. If characters are being output when the command is requested,
results are undefined and the output may be garbled.
Wait for the output to drain before setting new parameters.
This form should be used when changing parameters that affect output.
Wait for the output to drain,
then flush the input queue and set the new parameters.
termio Caveats
Only the first eight special control characters (see can be set or returned. The values of indices VEOL and VEOF are the same as indices
VTIME and VMIN respectively. Hence if is set, VEOL or VTIME is the additional end-of-line character and VEOF or VMIN is the end-of-file
character. If is clear, VEOL or VTIME is the inter-character-timer value and VEOF or VMIN is the minimum number of characters desired for
reads.
Structure-Independent Functions
The following functions which are independent of both the and structures are provided for controlling terminals. Refer to the appropriate
manual entries for details.
Structure-Independent Functions
Function Description
----------------------------------------------------
tcsendbreak() send a break
tcdrain() wait until output has drained
tcflush() flush input or output queue or both
tcflow() suspend or resume input or output
tcgetpgrp() get foreground process group id
tcsetpgrp() set foreground process group id
tcgetsid() get session id
System Asynchronous I/O IOCTL Commands
The following system calls provide for system asynchronous I/O and have the form:
Commands using this form are:
If the integer referenced by
arg is non-zero, system asynchronous I/O is enabled; that is, enable to be sent to the process currently desig-
nated with (see below) whenever the terminal device file status changes from "no read data available" to "read
data available". If no process has been designated with enable to be sent to the first process that opened the
terminal device file.
If the designated process has exited, the signal is not sent to any process.
If the integer referenced by arg is 0, system asynchronous I/O is disabled.
The default on open of a terminal device file is that system asynchronous I/O is disabled.
The integer referenced by
arg is set to 1 if system asynchronous I/O is enabled. Otherwise, the integer referenced by arg is set to 0.
Set the process ID that will receive the signals due to system asynchronous I/O to the value of the integer referenced by arg.
If no process can be found corresponding to that specified by the integer referenced by arg, the call returns -1
with set to A user with appropriate privileges can designate that any process receive the signals. If the
request is not made by a user with appropriate privileges and the calling process does not either designate that
itself or another process whose real, saved, or effective user ID matches its real or effective user ID or the
calling process does not designate a process that is a descendant of the calling process to receive the signals,
the call returns -1 with set to See privileges(5) for more information about privileged access on systems that
support fine-grained privileges.
If the designated process subsequently exits, the signal is not sent to any process.
The default on open of a terminal device file is that the process performing the first open is set to receive
the signals.
The integer referenced by
arg is set to the process ID designated to receive signals.
Line Control IOCTL Commands
Several system calls control input and output. Some of these calls have the form:
Commands using this form are:
Wait for the output to drain.
If arg is 0, send a break (zero bits for at least 0.25 seconds). The function performs the same function (see
tcsendbreak(3C)).
Start/stop control.
If arg is 0, suspend output; if 1, restart suspended output; if 2, transmit a STOP character; if 3, transmit a START
character. If any other value is given for arg, the call returns -1 with set to The function performs the same func-
tions (see tcflow(3C)).
If arg is 0, flush the input queue; if 1, flush the output queue; if 2, flush both the input and output queues. If any
other value is given for arg, the call returns -1 with set to The function performs the same functions (see
tcflush(3C)).
Sending a BREAK is accomplished by holding the data transmit line at a SPACE or logical zero condition for at least
0.25 seconds. During this interval, data can be sent to the device, but because of serial data interface limita-
tions, the BREAK takes precedence over all data. Thus, all data sent to a device during a BREAK is lost. This
includes system-generated XON/XOFF characters used for input flow control. Note also that a delay in transmission of
the XOFF flow control character until after the BREAK is terminated could still result in data overflow because the
flow control character may not be sent soon enough.
Other calls have the form:
Commands using this form are:
Returns in the integer referenced by
arg the number of characters immediately readable from the terminal device file. This command is allowed from a
background process; however, the data itself cannot be read from a background process.
Non-blocking I/O IOCTL Commands
Non-blocking I/O is easily provided via the and flags available in both open(2) and fcntl(2). The commands in this section are provided
for backward compatibility with previously developed applications. system calls that provide a style of non-blocking I/O different from
and have the form:
Commands using this form are:
If the integer referenced by
arg is non-zero, -style non-blocking I/O is enabled; that is, subsequent reads and writes to the terminal device file
are handled in a non-blocking manner (see below). If the integer referenced by arg is 0, -style non-blocking I/O is
disabled.
For reads, -style non-blocking I/O prevents all read requests to that device file from blocking, whether the requests
succeed or fail. Such a read request completes in one of three ways:
o If there is enough data available to satisfy the entire request, the read completes successfully, having read
all of the data, and returns the number of characters read;
o If there is not enough data available to satisfy the entire request, the read completes successfully, having
read as much data as possible, and returns the number of characters read;
o If there is no data available, the read returns -1 with set to
For writes, -style non-blocking I/O prevents all write requests to that device file from blocking, whether the
requests succeed or fail. Such a write request completes in one of three ways:
o If there is enough space available in the system to buffer all the data, the write completes successfully, hav-
ing written out all of the data, and returns the number of characters written;
o If there is not enough space in the buffer to write out the entire request, the write completes successfully,
having written as much data as possible, and returns the number of characters written;
o If there is no space in the buffer, the write returns -1 with set to
To prohibit -style non-blocking I/O from interfering with the and flags (see open(2) and fcntl(2)), the functionality
of and always supersedes the functionality of -style non-blocking I/O. This means that if either or is set, the
driver performs read requests in accordance with the definition of or When both and are clear, the definition of
-style non-blocking I/O applies.
The default on open of a terminal device file is that -style non-blocking I/O is disabled.
The integer referenced by
arg is set to 1, if -style non-blocking I/O is enabled. Otherwise, the integer referenced by arg is set to 0.
Process Group Control IOCTL Commands
The process group control features described here (except for setting and getting the delayed stop process character) are easily imple-
mented using the functions and (see tcattribute(3C), tcgetpgrp(3C), tcsetpgrp(3C), and tcgetsid(3C) respectively).
The following structure, used with process group control, is defined in
struct ltchars {
unsigned char t_suspc; /* stop process character*/
unsigned char t_dsuspc; /* delayed stop process character*/
unsigned char t_rprntc; /* reserved; must be '_POSIX_VDISABLE'*/
unsigned char t_flushc; /* reserved; must be '_POSIX_VDISABLE'*/
unsigned char t_werasc; /* reserved; must be '_POSIX_VDISABLE'*/
unsigned char t_lnextc; /* reserved; must be '_POSIX_VDISABLE'*/
};
The initial value for all these characters is which causes them to be disabled. The meaning for each character is as follows:
Suspend the foreground process group.
A suspend signal is sent to all processes in the foreground process group. Normally, each process is forced to stop,
but arrangements can be made to either ignore or block the signal, or to receive a trap to an agreed-upon location;
see signal(2) and signal(5). When enabled, the typical value for this character is Control-Z or ASCII SUB. Setting
or getting is equivalent to setting or getting the SUSP special control character.
Same as t_suspc, except that the suspend signal is sent when a process reads the character, rather than when the character is
typed. When enabled, the typical value for this character is Control-Y or ASCII EM.
Attempts to set any of the reserved characters to a value other than cause to return -1 with set to with no change in value of the reserved
character.
system calls that use the above structure have the form:
Commands using this form are:
Get the process group control characters and store them in the
ltchars structure referenced by arg. This command is allowed from a background process. However, the information
may be subsequently changed by a foreground process.
Set the process group control characters
from the structure referenced by arg.
Additional process group control system calls have the form:
Commands using this form are:
Returns in the integer referenced by
arg the foreground process group associated with the terminal. This command is allowed from a background process.
However, the information may be subsequently changed by a foreground process. This feature is easily implemented
using the function (see tcgetpgrp(3C)).
If the call fails, it returns -1 and sets to one of the following values:
fildes is not a valid file descriptor.
The file associated with
fildes is not the controlling terminal, or the calling process does not have a controlling terminal.
The file associated with
fildes is the controlling terminal of the calling process, however, there is no foreground process
group defined for the controlling terminal.
Note: may not be returned in future releases. Behavior in cases where no foreground process group is
defined for the controlling terminal may change in future versions of the POSIX standard. Portable
applications, therefore, should not rely on this error condition.
Sets the foreground process group associated with the terminal
to the value referenced by arg. This feature is easily implemented using the function (see tcsetpgrp(3C)).
If the call fails, it returns -1 and sets to one of the following values:
fildes is not a valid file descriptor.
The process ID referenced by arg is not a supported value.
The calling process does not have a controlling terminal, or the
fildes is not the controlling terminal, or the controlling terminal is no longer associated with the
session of the calling process.
The process ID referenced by arg is a supported value but does not match the process group ID of a process in the
same session as the calling process.
Returns in the integer referenced by
arg the session ID of the terminal specified by fildes. This feature is easily implemented using the function (see
tcgetsid(3C)).
If the call fails, it returns -1 and sets to one of the following values:
fildes is not a valid file descriptor.
The device associated with
fildes is not a terminal.
The fildes is a terminal that is not allocated to a session.
Get the process group control mode word
and store it in the int referenced by arg. This command is allowed from a background process; however, the informa-
tion may be subsequently changed by a foreground process.
Set the process group control mode word to the value of the int referenced by
arg.
Use the int referenced by
arg as a mask of bits to set in the process group control mode word.
Use the int referenced by
arg as a mask of bits to clear in the process group control mode word.
The following bit is defined in the process group control mode word:
Send for background writes.
Setting or clearing is equivalent to setting or clearing the flag (see If is set and a process is not in the foreground process group of
its controlling terminal, a write by the process to its controlling terminal may be denied (see
Terminal Size IOCTL Commands
The following system calls are used to get and set terminal size information for the terminal referenced by fildes. These system calls use
the structure to get and set the terminal size information. The structure, defined in has the following members :
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 */
The initial values for all elements of terminal size are zero. The values for terminal size are neither set nor used by the general termi-
nal interface, and have no effect on the functionality of the general terminal interface. The values for terminal size are set and used
only by applications that access them through the terminal-size system calls (see ioctl(2)).
system calls that use the above structure have the form:
Commands using this form are:
Get the terminal size values and store them in the
structure referenced by arg. This command is allowed from a background process.
Set the terminal size values from the
structure referenced by arg. If any of the new values differ from previous values, a signal is sent to all processes
in the terminal's foreground process group.
Console Output Redirection IOCTL Command
Output which would normally be sent to the system console may be redirected to any other TTY device or pseudo-device in the system. The
system call used to control console output redirection has the form:
The command using this form is:
Redirect system console output.
Any output that would normally be sent to the system console, either through kernel printf requests, or through the
console special file, will instead be sent to the terminal referenced by fildes. The value of arg is ignored. The
user must have the privilege to execute this request. Otherwise, the call returns -1 with set to If the console out-
put has not been redirected to a different device by a later call to this command, it is redirected back to the phys-
ical console device when fildes is closed.
WARNINGS
Various HP-UX implementations use non-serial interfaces that look like terminals (such as bit-mapped graphics displays) or ``smart cards''
that cannot implement the exact capabilities described above. Therefore, not all systems can exactly meet the standard stated above. Each
implementation is required to state any deviations from the standard as part of its system-specific documentation.
is similar to BSD 4.2 with the addition of provisions for security.
is of HP origin, complements and allows saving and restoring system asynchronous I/O TTY states for command inter-
preter processes.
is similar to BSD 4.2 with additional provisions for security.
is similar to BSD 4.2 Note also the difference that the BSD 4.2 version of this functionality used process groups, while the
HP-UX version only uses processes.
is the same as BSD 4.2 except that it does not interfere with the or and flags.
is of HP origin, complements
and allows saving and restoring the -style non-blocking I/O TTY state for command interpreter processes.
The general terminal interface uses a system resource known as a to store data being transmitted or received through a communications port.
These cblocks are continuously used and freed for reuse as data pass through the system. If too few cblocks are configured in the system,
the cblock pool may be temporarily or permanently exhausted, and data loss, system hangs, or reduced system performance can result.
If cblock exhaustion is suspected, you can examine the system message buffer with (see dmesg(1M)) for messages indicating cblock exhaustion
has occurred. Or, you can use (see adb(1)) if examining the corefile of a dump. The message format is
where n indicates the number of times the operating system has requested a cblock and none could be provided. If this message is observed,
the kernel should be reconfigured to generate a larger number of cblocks.
A cblock is 32 bytes in length. The default number of cblocks configured in the system is defined to be 8292.
This can be overridden by using the optional tunable system parameter to specify the desired number of cblocks to be used in the system.
or kctune(1M) may be used to change the value.
DEPENDENCIES
Workstations
Built-in serial ports on workstation machines support the following additional baud rate settings: 57600, and 115200. An RS-232-to-RS-422
converter may be required to achieve practical cable lengths at these baud rates (because RS-232 only specifies up to 19200 baud).
Timed delays are not supported.
Built-in serial ports on workstation systems have RTS and CTS flow control capability, configurable receive FIFO trigger levels, and a con-
figurable transmit limit. RTS/CTS hardware handshaking can be enabled through a bit in the device file minor number, through an call (see
termiox(7)), or through the command (see stty(1)).
The receive FIFO trigger level is configurable through two bits in the device file minor number. The receive FIFO trigger level is used to
set the level at which a receive interrupt is generated to the system. Setting a smaller value for the receive FIFO trigger level enables
the system to react more quickly to receipt of characters. However, using a smaller trigger level increases system overhead to process the
additional interrupts. A higher receive FIFO trigger level reduces the system interrupt overhead for heavy inbound data traffic at the
cost of less time for the system to read data from the hardware before receive FIFOs are overrun. When using RTS flow control, the receive
FIFO trigger level also determines the point at which the hardware lowers RTS to protect the receive FIFO. Use of a higher receive FIFO
trigger level also reduces XOFF flow control responsiveness because, under light inbound data flow conditions, receipt of the XOFF charac-
ter by the system is slightly delayed. Choice of the appropriate receive FIFO trigger level should be based upon how the serial port is to
be used. For most applications a receive FIFO trigger level of 8 (c3,c2 = 10) is suggested.
Two bits in the device file minor number specify the transmit limit, the number of characters which are successively loaded into the trans-
mit FIFO. Setting a smaller transmit limit allows the transmitter to be more responsive to flow control either from receipt of an XOFF
character or de-assertion of CTS at the cost of increased system interrupt overhead. Setting a larger transmit limit reduces interrupt
overhead but is not as responsive to flow control since the remainder of the transmit FIFO can be transmitted even after the transmitter is
flow controlled. When communicating with devices which have little tolerance for data receipt after flow control, one must choose the
transmit limit appropriately. Workstation device file minor numbers take the form:
where:
II = Two hexadecimal digits (8 bits) to indicate the instance of the serial interface.
C = One hexadecimal digit (4 bits) for FIFO control. Values for each bit are as follows:
+---------------------------+-----------------+
|Receive FIFO Trigger Level | Transmit Limit |
+-------+--------+----------+----+----+-------+
| c3 | c2 | Level | c1 | c0 | Limit |
+-------+--------+----------+----+----+-------+
| 0 | 0 | 1 | 0 | 0 | 1 |
| 0 | 1 | 4 | 0 | 1 | 4 |
| 1 | 0 | 8 | 1 | 0 | 8 |
| 1 | 1 | 14 | 1 | 1 | 12 |
+-------+--------+----------+----+----+-------+
H = One hexadecimal digit (4 bits) which controls diagnostic access and hardware flow control.
+-----+---------------------------------------+
|Bit | Value |
+-----+---------------------------------------+
| h3 | Diagnostic telephony access |
| h2 | Reserved |
| h1 | Reserved |
| h0 | Enables RTS/CTS hardware flow control |
+-----+---------------------------------------+
M = One hexadecimal digit (4 bits) to determine the port access type. Values for each bit are as follows:
+-----+--------------------------------+
|Bit | Value |
+-----+--------------------------------+
| m3 | TI/ALP |
| m2 | 0 = Simple protocol (U.S.), |
| | 1 = CCITT protocol (Europe) |
|m1m0 | 00 = Direct |
| | 01 = Dial-out modem |
| | 10 = Dial-in modem |
| | 11 = Invalid |
+-----+--------------------------------+
Servers
Timed output delays are not directly supported. If used, an appropriate number of fill characters (based on the current baud rate) is out-
put. The total time to output the fill characters is at least as long as the time requested.
The system specified input flow control values are as follows: low water mark is 60, high water mark is 180, and maximum allowed input is
512.
The HP 98196A (formerly 27140A option 800) interface does not support the following hardware settings:
The HP A1703-60003 and the
HP 28639-60001 interfaces do not support baud rates above 9600. Furthermore, changing the following hardware settings on port 0
from the default (9600 baud, 8 bit characters, 1 stop bit, no parity) is not supported:
The HP J2094A interface does not support baud rates above 19200.
The HP J2094A supports RTS and CTS flow control. The RTS/CTS hardware handshaking can be enabled through a bit in the device file minor
number, through an call (see termiox(7)), or through the command (see stty(1)). Server device file minor numbers take the form:
where:
II = Two hexadecimal digits (8 bits) to indicate the instance of the serial interface.
PP = Two hexadecimal digits (8 bits) to indicate the port number of this device on the serial interface.
H = One hexadecimal digit (4 bits) which controls diagnostic access and hardware flow control (HP J2094A only).
+-----+---------------------------------------+
|Bit | Value |
+-----+---------------------------------------+
| h3 | Card diagnostic |
| h2 | Port diagnostic |
| h1 | Reserved |
| h0 | Enables RTS/CTS hardware flow control |
+-----+---------------------------------------+
M = One hexadecimal digit (4 bits) for the port access type. Values for each bit are as follows:
+-----+--------------------------------+
|Bit | Value |
+-----+--------------------------------+
| m3 | TI/ALP |
| m2 | 0 = Simple protocol (U.S.), |
| | 1 = CCITT protocol (Europe) |
|m1m0 | 00 = Direct |
| | 01 = Dial-out modem |
| | 10 = Dial-in modem |
| | 11 = Invalid |
+-----+--------------------------------+
AUTHOR
was developed by HP and the IEEE Computer Society.
was developed by HP, AT&T, and the University of California, Berkeley.
FILES
SEE ALSO
adb(1), shl(1), stty(1), dmesg(1M), kctune(1M), mknod(1M), fork(2), ioctl(2), setpgid(2), setsid(2), signal(2), stty(2), cfspeed(3C), tcat-
tribute(3C), tccontrol(3C), tcgetpgrp(3C), tcgetsid(3C), tcsetpgrp(3C), privileges(5), signal(5), unistd(5), modem(7), sttyV6(7),
termiox(7), tty(7).
STANDARDS CONFORMANCE
termio(7)