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Manual page for ldterm(7M)

ldterm - standard STREAMS terminal line discipline module

SYNOPSIS

#include <sys/stream.h>
#include <sys/termios.h>

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

DESCRIPTION

ldterm is a STREAMS module that provides most of the termio.7i terminal interface. This module does not perform the low-level device control functions specified by flags in the c_cflag word of the termio/termios structure or by the IGNBRK, IGNPAR, PARMRK, or INPCK flags in the c_iflag word of the termio/termios structure; those functions must be performed by the driver or by modules pushed below the ldterm module. ldterm performs all other termio/termios functions; some of them, however, require the cooperation of the driver or modules pushed below ldterm and may not be performed in some cases. These include the IXOFF flag in the c_iflag word and the delays specified in the c_oflag word.

ldterm also handles Extended Unix Code (EUC) and multi-byte characters.

The remainder of this section describes the processing of various STREAMS messages on the read- and write-side.

Read-side Behavior

Various types of STREAMS messages are processed as follows:

M_BREAK: When this message is received, depending on the state of the BRKINT flag, either an interrupt signal is generated or the message is treated as if it were an M_DATA message containing a single ASCII NUL character.
M_DATA: This message is normally processed using the standard termio input processing. If the ICANON flag is set, a single input record (``line'') is accumulated in an internal buffer and sent upstream when a line-terminating character is received. If the ICANON flag is not set, other input processing is performed and the processed data are passed upstream.
: If output is to be stopped or started as a result of the arrival of characters (usually CNTRL-Q and CNTRL-S), M_STOP and M_START messages are sent downstream. If the IXOFF flag is set and input is to be stopped or started as a result of flow-control considerations, M_STOPI and M_STARTI messages are sent downstream.
: M_DATA messages are sent downstream, as necessary, to perform echoing.
: If a signal is to be generated, an M_FLUSH message with a flag byte of FLUSHR is placed on the read queue. If the signal is also to flush output, an M_FLUSH message with a flag byte of FLUSHW is sent downstream.
M_CTL: If the size of the data buffer associated with the message is the size of struct iocblk, ldterm will perform functional negotiation to determine where the termio.7i processing is to be done. If the command field of the iocblk structure (ioc_cmd) is set to MC_NO_CANON, the input canonical processing normally performed on M_DATA messages is disabled and those messages are passed upstream unmodified; this is for the use of modules or drivers that perform their own input processing, such as a pseudo-terminal in TIOCREMOTE mode connected to a program that performs this processing. If the command is MC_DO_CANON, all input processing is enabled. If the command is MC_PART_CANON, then an M_DATA message containing a termios structure is expected to be attached to the original M_CTL message. The ldterm module will examine the iflag, oflag, and lflag fields of the termios structure and from then on will process only those flags which have not been turned ON. If none of the above commands are found, the message is ignored; in any case, the message is passed upstream.
M_FLUSH: The read queue of the module is flushed of all its data messages and all data in the record being accumulated are also flushed. The message is passed upstream.
M_IOCACK: The data contained within the message, which is to be returned to the process, are augmented if necessary, and the message is passed upstream.

All other messages are passed upstream unchanged.

Write-side Behavior

Various types of STREAMS messages are processed as follows:

M_FLUSH: The write queue of the module is flushed of all its data messages and the message is passed downstream.
M_IOCTL: The function of this ioctl is performed and the message is passed downstream in most cases. The TCFLSH and TCXONC ioctls can be performed entirely in the ldterm module, so the reply is sent upstream and the message is not passed downstream.
M_DATA: If the OPOST flag is set, or both the XCASE and ICANON flags are set, output processing is performed and the processed message is passed downstream along with any M_DELAY messages generated. Otherwise, the message is passed downstream without change.

All other messages are passed downstream unchanged.

IOCTLS

ldterm processes the following TRANSPARENT ioctls. All others are passed downstream.