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ptem(7)

HP-UX 11i Version 3: February 2007
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NAME

ptem — STREAMS pty (pesudo-terminal) Emulation module

SYNOPSIS

#include <sys/stropts.h>

int ioctl(fd_slave, I_PUSH, "ptem");

DESCRIPTION

ptem is a STREAMS module that emulates a terminal when used in conjunction with ldterm (STREAMS line discipline) and pts (STREAMS slave pty driver). The ptem module normally sits above pts and below ldterm. The user process must push the ptem module onto the slave side of the pty with a call to the STREAMS I_PUSH ioctl(2) system call before ldterm is pushed. ptem is responsible for processing all of the terminal ioctl commands that are passed downstream from ldterm or from ptm (STREAMS pty master driver).

ldterm and ptem together provide a real terminal behavior for the STREAMS pty slave. However, some of the terminal ioctl commands are ignored and cause only an acknowledgement of the command since there is no real terminal or modem in the pty subsystem. In fact, none of the flags in the c_clfag field of the termio or termios structures, (which is used by the TCSETA or TCSETS ioctls, respectively), have any effect on the pty except if the baud rate is set to zero. Setting the baud rate to zero will have the effect of hanging up the pty connection. Similarly, the parity or delay flags in the c_iflag field will not have any effect at all on the pty.

As a summary, the ptem module performs the following tasks:

  • The following ioctls are processed, if appropriate, and acknowledged by sending an M_IOCACK message upstream when they are received on ptem's write queue:

    TCSETA, TCSETAW, TCSETAF, TCSETS, TCSETSW, TCSETSF, TCGETA, TCGETS, and TCSBRK.

  • Keeps track of the window size needed for the TIOCSWINSZ, TIOCGWINSZ, and JWINSIZE ioctls.

  • Upon receiving any other ioctl on its write queue, ptem acknowledges them negatively by sending an M_IOCNAK message upstream.

  • The following ioctls are passed downstream by ptem after they have been processed:

    TCSETA, TCSETAW, TCSETAF, TCSETS, TCSETSW, TCSETSF, TCSBRK, and TIOCSWINSZ.

  • Any M_IOCNAK message that is received on ptem's read queue will be freed in case the pckt module is not pushed on the ptm and the above ioctls get to the pty master STREAMS head, which would then send an M_IOCNAK message downstream.

  • When ptem is opened and all conditions for setting up a controlling terminal are met, it sends an M_SETOPTS message (with the SO_ISATTY flag set) upstream to the STREAMS head to allocate a controlling terminal.

  • Upon receiving an M_IOCTL message of type TCSBRK on its read queue, ptem sends an M_IOCACK message downstream and an M_BREAK message upstream.

  • When an ioctl message is received on its write queue to set the baud rate to zero (e.g. TCSETA with CBAUD set to B0), ptem sends an M_IOCACK message upstream and a zero-length message downstream to be read by the pty master process.

  • When an M_IOCTL message of type TIOCSIGNAL is received on its read queue, ptem sends an M_IOCACK message downstream and an M_PCSIG message upstream with the signal number set to the same value used in the M_IOCTL message.

  • When an M_IOCTL message of type TIOCREMOTE is received on its read queue, ptem sends an M_IOCACK message downstream and an M_CTL message (with ioc_cmd set to MC_DO_CANON or MC_NO_CANON) upstream to enable or disable the input processing on ldterm.

  • When an M_DELAY message is received on its read or write queue, ptem simply discards the message without any action.

  • When an M_IOCTL message of type JWINSIZE is received on its write queue and if the values in the jwinsize structure in ptem are not zero, ptem sends an M_IOCACK message upstream with the jwinsize structure. If the values are zero, ptem sends an M_IOCNAK message upstream.

  • When an M_IOCTL message of type TIOCGWINSZ is received on its write queue and if the values in the winsize structure in ptem are not zero, ptem sends an M_IOCACK message upstream with the winsize structure. If the values are zero, ptem sends an M_IOCNAK message upstream.

  • When an M_IOCTL message of type TIOCSWINSZ is received in its write queue, ptem saves the information passed to it in the winsize structure and sends an M_PCSIG (with the signal number set to SIGWINCH) upstream to the pty slave process if the window size is changed.

  • When an M_IOCTL message of type TIOCGWINSZ is received on its read queue and if the values in the winsize structure in ptem are not zero, ptem sends an M_IOCACK message downstream with the winsize structure. If the values are zero, ptem sends an M_IOCNAK message downstream.

  • When an M_IOCTL message of type TIOCSWINSZ is received in its read queue, ptem saves the information passed to it in the winsize structure and sends an M_PCSIG (with the signal number is set to SIGWINCH) upstream to the pty slave process if the window size is changed.

  • All other messages not mentioned above are passed to the next module or driver.

AUTHOR

ptem was developed by HP.

SEE ALSO

ioctl(2), streamio(7), ptm(7), pts(7), ldterm(7).



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