termio.7 (2010 09)

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termio(7) 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

rlogin (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

getty

(see getty (1M)) and become a user’s standard input, standard output, and standard error ﬁles.

If both the

O_NDELAY and O_NONBLOCK ﬂags (see open(2)) are clear, an open blocks until the type of

modem connection requested (see modem(7)) is completed. If either the

O_NDELAY or O_NONBLOCK

ﬂag is set, an open succeeds and return immediately without waiting for the requested modem connection

to complete. The CLOCAL ﬂag (see Control Modes ) 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 session. 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 con-

trolling 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 allocated by the session leader. If a session

leader has no controlling terminal and opens a terminal device ﬁle that is not already associated with a

session without using the

O_NOCTTY 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

fork() (see fork (2)). A process relin-

quishes its controlling terminal if it creates a new session with setsid() or setpgrp() (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 ses-

sion, allowing it to be acquired by a new session leader. A

SIGHUP 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 Terminal Access Control ) with attempts to access the

terminal treated as if a modem disconnect had been sensed.

Terminal Access Control

Read operations are allowed (see Input Processing and Reading Data ) from processes in the foreground

process group of their controlling terminal. If a process is not in the foreground process group of its con-

trolling terminal, the process and all member’s of its process group are considered to be in a background

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

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (22 pages)

PAGE 1
termio(7) 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 rlogin (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.
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termio(7) termio(7) blocking the SIGTTIN 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, read() returns −1 with errno set to EIO 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 SIGTTIN signal.
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termio(7) termio(7) When the MAX_CANON 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 Special Characters ), is received. This processing 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.
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termio(7) termio(7) 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.
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termio(7) termio(7) waiting, (that is, the EOF occurred at the beginning of a line) a character count of zero is returned from read(), representing an end-of-file indication. If ICANON is enabled, the EOF character is discarded when processed. If ICANON is not enabled, the EOF character is treated as a normal data character. NL (ASCII LF) special character on input and is recognized if ICANON flag is enabled. It is the line delimiter (\n).
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termio(7) termio(7) 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 _POSIX_VDISABLE to maintain binary compatibility with previous releases of HP-UX.
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termio(7) ERASE KILL EOF EOL EOL2 MIN TIME SUSP START STOP WERASE LNEXT DSUSP termio(7) VERASE VKILL VEOF VEOL VEOL2 VMIN VTIME VSUSP VSTART VSTOP VWERASE VLNEXT VDSUSP # @ Control-D NUL disabled NUL Control-D disabled Control-Q Control-S disabled disabled disabled termio Structure The termio structure has been superseded by the termios structure and is provided for backward compatibility with prior applications (see termio Caveats ). The structure is defined in the header file
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termio(7) termio(7) If PARMRK is set, and IGNPAR is clear, a character with a framing or parity error (other than break) is read as the three-character sequence: \377, \0, X, where X is the data of the character received in error. To avoid ambiguity in this case, if ISTRIP is clear, a valid character of \377 is read as \377, \377. If both PARMRK and IGNPAR are clear, a framing or parity error (other than break) is read as the character \0. If INPCK is set, input parity checking is enabled.
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termio(7) termio(7) water mark. When ICANON is set and the input stream contains more characters between line delimiters than the high water mark allows, there is no guarantee that IXOFF can prevent buffer overflow and data loss, because the STOP character may not be sent in time, if at all. If IMAXBEL 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.
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termio(7) termio(7) 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 ONLRET is set, carriage-return delays are used instead of the new-line delays. If OFILL 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 OFILL is set, delay type 1 transmits two fill characters; type 2, four fill characters.
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termio(7) termio(7) If CLOCAL is set, a connection does not depend on the state of the modem status lines. If CLOCAL is clear, the modem status lines are monitored. Under normal circumstances, a call to read() waits for a modem connection to complete. However, if either the O_NDELAY or the O_NONBLOCK flags are set or CLOCAL is set, the open() returns immediately without waiting for the connection.
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termio(7) termio(7) When 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 as described in Canonical Mode Input Processing. Furthermore, the following echo functions are possible. If ECHO and ECHOE 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.
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termio(7) termio(7) VKILL VMIN VQUIT VSTART VSTOP VSUSP VDSUSP VTIME VLNEXT VQUIT VSTART VSTOP VSUSP VDSUSP VLNEXT KILL character MIN value QUIT character START character STOP character SUSP character DSUSP character TIME value LNEXT character termios Structure-Related Functions The following functions are provided when using the termios structure.
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termio(7) termio(7) wait until output has drained flush input or output queue or both suspend or resume input or output get foreground process group id set foreground process group id get session id tcdrain() tcflush() tcflow() tcgetpgrp() tcsetpgrp() tcgetsid() System Asynchronous I/O IOCTL Commands The following ioctl() system calls provide for system asynchronous I/O and have the form: ioctl (fildes, command, arg) int *arg; Commands using this form are: FIOSSAIOSTAT If the integer referenced by ar
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termio(7) termio(7) function performs the same functions (see tcflow(3C)). TCFLSH 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 errno set to [EINVAL]. The tcflush() 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.
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termio(7) termio(7) • If there is no space in the buffer, the write returns −1 with errno set to [EWOULDBLOCK]. To prohibit FIOSNBIO-style non-blocking I/O from interfering with the O_NONBLOCK and O_NDELAY flags (see open (2) and fcntl (2)), the functionality of O_NONBLOCK and O_NDELAY always supersedes the functionality of FIOSNBIO-style non-blocking I/O.
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termio(7) TIOCGPGRP termio(7) 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 tcgetpgrp() function (see tcgetpgrp (3C)). If the ioctl() call fails, it returns −1 and sets errno to one of the following values: [EBADF] fildes is not a valid file descriptor.
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termio(7) termio(7) the process to its controlling terminal may be denied (see Terminal Access Control ). Terminal Size IOCTL Commands The following ioctl() system calls are used to get and set terminal size information for the terminal referenced by fildes . These ioctl() system calls use the winsize structure to get and set the terminal size information. The winsize structure, defined in
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termio(7) termio(7) processes. The general terminal interface uses a system resource known as a cblock 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.
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termio(7) C = termio(7) One hexadecimal digit (4 bits) for FIFO control. Values for each bit are as follows: Receive FIFO Trigger Level c3 c2 Level 0 0 1 0 1 4 1 0 8 1 1 14 H = One hexadecimal digit (4 bits) which controls diagnostic access and hardware flow control. Bit h3 h2 h1 h0 M = Transmit Limit c1 c0 Limit 0 0 1 0 1 4 1 0 8 1 1 12 Value Diagnostic telephony access Reserved Reserved Enables RTS/CTS hardware flow control One hexadecimal digit (4 bits) to determine the port access type.
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termio(7) H = termio(7) One hexadecimal digit (4 bits) which controls diagnostic access and hardware flow control (HP J2094A only). Bit h3 h2 h1 h0 M = Value Card diagnostic Port diagnostic Reserved Enables RTS/CTS hardware flow control One hexadecimal digit (4 bits) for the port access type. Values for each bit are as follows: Bit m3 m2 m1m0 Value TI/ALP 0 = Simple protocol (U.S.
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(Notes) A (Notes) tA 22 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010