ldterm.7 (2010 09)

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ldterm(7) ldterm(7)

NAME

ldterm - standard STREAMS terminal line discipline module

SYNOPSIS

#include <sys/stream.h>

#include <sys/stropts.h>

#include <sys/termios.h>

#include <sys/bsdtty.h>

#include <sys/ttold.h>

#include <sys/strtio.h>

#include <sys/eucioctl.h>

int ioctl( fd, I_PUSH, "ldterm");

DESCRIPTION

ldterm is a STREAMS module that supplies the line discipline for streams-based terminal or pseudo-

terminal device drivers. This module provides most of the functions of the general terminal interface

described in termio (7). However, it does not perform the low-level device control functions speciﬁed by

the c_cflag word deﬁned by the POSIX

termios structure or the System V termio structure

(deﬁned in

termios.h and termio.h, respectively). Also, some operations require the cooperation of

the modules and drivers pushed below the ldterm module in a tty or pty (slave) stream. This man page

only covers ldterm speciﬁc interface here and refers to the readers to termio (7) for the detail terminal

interface.

Internally, the

ldterm module uses the Extended UNIX Code (EUC) character encoding scheme. This

encoding scheme enables the ldterm module to process multibyte characters as well as simple 8-bit

characters. It correctly handles backspacing, word erasing, and tab expansion for multibyte EUC charac-

ters.

The

ldterm module provides standard terminal operation consistent with the behavior speciﬁed by

POSIX 1003.1 and System V Interface Deﬁnition (SVID) Third Edition. It also provides compatibility

with the behavior of the BSD 4.3 line discipline. Notice that on other STREAMS systems, the BSD 4.3

compatibility feature is usually provided by a separate STREAMS module called

ttcompat.Hence,

applications on HP-UX need not push

ttcompat on top of ldterm to get BSD 4.3 compatibility. In fact,

the ttcompat module is not provided on the HP-UX system at all.

The

ldterm module normally sits above either a STREAMS tty driver or a STREAMS pty slave driver.

The user issues an STREAMS I_PUSH ioctl (2) system call to push ldterm onto the stream once the

STREAMS tty or STREAMS pty slave device is opened.

STREAMS Messages

The

ldterm module processes various types of STREAMS messages. The line discipline will act on any

of the following message types. Any others that the module receives, however, are passed onto the next

module on the stream.

Read-side Behavior

ldterm processes the following STREAMS messages on its input stream:

M_FLUSH If FLUSHR is set, the read put routine ﬂushes the read queue, discards characters in the input

message buffers, and discards any partially buffered multibyte EUC characters. Then, it for-

wards the message upstream.

M_BREAK The read put routine processes the message according to POSIX rules for processing BREAK

events, parity errors, and framing errors and signal generation (see termio (7) for detail). If

there is no data in the message, the message is assumed to represent an input BREAK event,

which is represented by a framing error with a character value of 0 (zero). If there is data in

the message, the data value is an integer that indicates the occurrence of an input BREAK

event, or a character received with a parity or framing error. The low-order 8 bits of the data

value is the byte that was read. If the TTY_PE ﬂag is set in the higher-order bits of this

integer, then a parity error was detected. If the TTY_FE ﬂag is set in the higher-order bits of

this integer, a framing error was detected.

After reading the data value, the read put routine discards the message.

M_DATA The read put routine processes the message according to the POSIX 1003.1 speciﬁcation, using

multibyte processing for backspacing, word erasing, and tab expansion as appropriate.

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

Summary of content (6 pages)

PAGE 1
ldterm(7) ldterm(7) NAME ldterm - standard STREAMS terminal line discipline module SYNOPSIS #include #include #include #include #include #include #include int ioctl( fd, I_PUSH, "ldterm"); DESCRIPTION ldterm is a STREAMS module that supplies the line discipline for streams-based terminal or pseudoterminal device drivers.
PAGE 2
ldterm(7) ldterm(7) It generates echo characters and places them in the output buffer to be sent downstream to the write queue. While processing incoming data, it scans for START and STOP characters and sends M_START, M_STOP messages downstream to the write queue, if needed. If the total number of buffered input characters is more than the high-water mark and IXOFF is set, the read put routine sends an M_STOPI message downstream.
PAGE 3
ldterm(7) ldterm(7) M_FLUSH The write put routine flushes the write queue and discards any buffered output data. Then, it forwards the message downstream. M_DATA The write service routine processes the data according to the POSIX 1003.1 specification output flags. It sends the processed characters downstream to the driver when the output queue fills up and all of the data is processed. M_IOCTL The write put routine validates the format of the M_IOCTL message and checks for known commands.
PAGE 4
ldterm(7) ldterm(7) processes it as for a TCGETS command, then converts the POSIX termios information into the System V termio information and replies. TCSBRK The ldterm module forwards this command downstream to be handled by the driver so that the driver has a chance to drain the data before sending an M_IOCACK message upstream. TCXONC This command controls the behavior of input/output flow control. If the argument is 0 and output is not already stopped, an M_STOP message is sent downstream.
PAGE 5
ldterm(7) ldterm(7) TIOCGETD In a BSD system, this command is used to get the current line discipline type. The command does not have much meaning in a STREAMS environment. The ldterm module replies with a value of 2 for binary compatibility, since ldterm supports job control. TIOCFLUSH This command flush the input or/and output streams similar to that of the TCFLSH command. The argument is a pointer to an int variable.
PAGE 6
ldterm(7) ldterm(7) (i.e. TCSETS). The original I/O control command and M_IOCTL message are stored for use on M_IOCACK. TIOCGLTC The ldterm module returns the ltchars information based on the interpretation of the current content of the POSIX termios structure maintained in ldterm. TIOCLBIS, TIOCLBIC, TIOCLSET These commands set the BSD 4.3 flags information, defined in . For TIOCLBIS and TIOCLBIC, the argument is a pointer to an int whose value is a mask containing flags to be set/clear.