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man:tty_ioctl

IOCTL_TTY(2) Linux Programmer's Manual IOCTL_TTY(2)

NAME

     ioctl_tty - ioctls for terminals and serial lines

SYNOPSIS

     #include <termios.h>
     int ioctl(int fd, int cmd, ...);

DESCRIPTION

     The  ioctl(2) call for terminals and serial ports accepts many possible
     command arguments.  Most require a third  argument,  of  varying  type,
     here called argp or arg.
     Use  of  ioctl makes for nonportable programs.  Use the POSIX interface
     described in termios(3) whenever possible.
 Get and set terminal attributes
     TCGETS    struct termios *argp
            Equivalent to tcgetattr(fd, argp).
            Get the current serial port settings.
     TCSETS    const struct termios *argp
            Equivalent to tcsetattr(fd, TCSANOW, argp).
            Set the current serial port settings.
     TCSETSW   const struct termios *argp
            Equivalent to tcsetattr(fd, TCSADRAIN, argp).
            Allow the output buffer to drain, and  set  the  current  serial
            port settings.
     TCSETSF   const struct termios *argp
            Equivalent to tcsetattr(fd, TCSAFLUSH, argp).
            Allow the output buffer to drain, discard pending input, and set
            the current serial port settings.
     The following four  ioctls  are  just  like  TCGETS,  TCSETS,  TCSETSW,
     TCSETSF,  except  that  they take a struct termio * instead of a struct
     termios *.
            TCGETA    struct termio *argp
            TCSETA    const struct termio *argp
            TCSETAW   const struct termio *argp
            TCSETAF   const struct termio *argp
 Locking the termios structure
     The termios structure of a terminal can be locked.  The lock is  itself
     a  termios  structure,  with nonzero bits or fields indicating a locked
     value.
     TIOCGLCKTRMIOS struct termios *argp
            Gets the locking status of the termios structure of  the  termi-
            nal.
     TIOCSLCKTRMIOS const struct termios *argp
            Sets  the  locking status of the termios structure of the termi-
            nal.  Only a process with the CAP_SYS_ADMIN  capability  can  do
            this.
 Get and set window size
     Window sizes are kept in the kernel, but not used by the kernel (except
     in the case of virtual consoles, where the kernel will update the  win-
     dow  size when the size of the virtual console changes, for example, by
     loading a new font).
     The following constants and structure are defined in <sys/ioctl.h>.
     TIOCGWINSZ     struct winsize *argp
            Get window size.
     TIOCSWINSZ     const struct winsize *argp
            Set window size.
     The struct used by these ioctls is defined as
         struct winsize {
             unsigned short ws_row;
             unsigned short ws_col;
             unsigned short ws_xpixel;   /* unused */
             unsigned short ws_ypixel;   /* unused */ };
     When the window size changes, a SIGWINCH signal is sent  to  the  fore-
     ground process group.
 Sending a break
     TCSBRK    int arg
            Equivalent to tcsendbreak(fd, arg).
            If  the terminal is using asynchronous serial data transmission,
            and arg is zero, then send a break (a stream of zero  bits)  for
            between  0.25  and  0.5  seconds.   If the terminal is not using
            asynchronous serial data transmission, then either  a  break  is
            sent,  or the function returns without doing anything.  When arg
            is nonzero, nobody knows what will happen.
            (SVr4, UnixWare, Solaris, Linux treat  tcsendbreak(fd,arg)  with
            nonzero arg like tcdrain(fd).  SunOS treats arg as a multiplier,
            and sends a stream of bits arg times as long as  done  for  zero
            arg.   DG/UX and AIX treat arg (when nonzero) as a time interval
            measured in milliseconds.  HP-UX ignores arg.)
     TCSBRKP   int arg
            So-called "POSIX version" of TCSBRK.  It treats nonzero arg as a
            timeinterval  measured in deciseconds, and does nothing when the
            driver does not support breaks.
     TIOCSBRK  void
            Turn break on, that is, start sending zero bits.
     TIOCCBRK  void
            Turn break off, that is, stop sending zero bits.
 Software flow control
     TCXONC    int arg
            Equivalent to tcflow(fd, arg).
            See tcflow(3) for the argument  values  TCOOFF,  TCOON,  TCIOFF,
            TCION.
 Buffer count and flushing
     FIONREAD  int *argp
            Get the number of bytes in the input buffer.
     TIOCINQ   int *argp
            Same as FIONREAD.
     TIOCOUTQ  int *argp
            Get the number of bytes in the output buffer.
     TCFLSH    int arg
            Equivalent to tcflush(fd, arg).
            See  tcflush(3)  for  the  argument  values  TCIFLUSH, TCOFLUSH,
            TCIOFLUSH.
 Faking input
     TIOCSTI   const char *argp
            Insert the given byte in the input queue.
 Redirecting console output
     TIOCCONS  void
            Redirect  output  that  would  have  gone  to  /dev/console   or
            /dev/tty0  to  the given terminal.  If that was a pseudoterminal
            master, send it to the slave.  In Linux before  version  2.6.10,
            anybody  can  do  this  as long as the output was not redirected
            yet; since version 2.6.10, only a process with the CAP_SYS_ADMIN
            capability  may do this.  If output was redirected already EBUSY
            is returned, but redirection can be stopped by using this  ioctl
            with fd pointing at /dev/console or /dev/tty0.
 Controlling terminal
     TIOCSCTTY int arg
            Make  the given terminal the controlling terminal of the calling
            process.  The calling process must be a session leader  and  not
            have  a controlling terminal already.  For this case, arg should
            be specified as zero.
            If this terminal is already the controlling terminal of  a  dif-
            ferent  session  group,  then the ioctl fails with EPERM, unless
            the caller has the CAP_SYS_ADMIN capability and arg equals 1, in
            which case the terminal is stolen, and all processes that had it
            as controlling terminal lose it.
     TIOCNOTTY void
            If the given terminal was the controlling terminal of the  call-
            ing  process, give up this controlling terminal.  If the process
            was session leader, then send SIGHUP and SIGCONT  to  the  fore-
            ground  process  group  and all processes in the current session
            lose their controlling terminal.
 Process group and session ID
     TIOCGPGRP pid_t *argp
            When successful, equivalent to *argp = tcgetpgrp(fd).
            Get the process group ID of the foreground process group on this
            terminal.
     TIOCSPGRP const pid_t *argp
            Equivalent to tcsetpgrp(fd, *argp).
            Set the foreground process group ID of this terminal.
     TIOCGSID  pid_t *argp
            Get  the  session ID of the given terminal.  This fails with the
            error ENOTTY if the terminal is not a master pseudoterminal  and
            not our controlling terminal.  Strange.
 Exclusive mode
     TIOCEXCL  void
            Put the terminal into exclusive mode.  No further open(2) opera-
            tions on the terminal are permitted.   (They  fail  with  EBUSY,
            except for a process with the CAP_SYS_ADMIN capability.)
     TIOCGEXCL int *argp
            (since  Linux  3.8)  If  the  terminal is currently in exclusive
            mode, place a nonzero value in the location pointed to by  argp;
            otherwise, place zero in *argp.
     TIOCNXCL  void
            Disable exclusive mode.
 Line discipline
     TIOCGETD  int *argp
            Get the line discipline of the terminal.
     TIOCSETD  const int *argp
            Set the line discipline of the terminal.
 Pseudoterminal ioctls
     TIOCPKT   const int *argp
            Enable  (when  *argp is nonzero) or disable packet mode.  Can be
            applied to the master side of a pseudoterminal  only  (and  will
            return  ENOTTY  otherwise).   In  packet  mode,  each subsequent
            read(2) will return a  packet  that  either  contains  a  single
            nonzero control byte, or has a single byte containing zero (' ')
            followed by data written on the slave side of  the  pseudotermi-
            nal.   If the first byte is not TIOCPKT_DATA (0), it is an OR of
            one or more of the following bits:
            TIOCPKT_FLUSHREAD   The read queue for the terminal is flushed.
            TIOCPKT_FLUSHWRITE  The write queue for the terminal is flushed.
            TIOCPKT_STOP        Output to the terminal is stopped.
            TIOCPKT_START       Output to the terminal is restarted.
            TIOCPKT_DOSTOP      The start and stop characters are ^S/^Q.
            TIOCPKT_NOSTOP      The start and stop characters are not ^S/^Q.
            While this mode is in use, the presence of control status infor-
            mation  to  be  read  from  the master side may be detected by a
            select(2) for exceptional conditions or a poll(2) for the  POLL-
            PRI event.
            This  mode  is  used  by rlogin(1) and rlogind(8) to implement a
            remote-echoed, locally ^S/^Q flow-controlled remote login.
     TIOCGPKT  const int *argp
            (since Linux 3.8) Return the current packet mode setting in  the
            integer pointed to by argp.
     TIOCSPTLCK     int *argp
            Set (if *argp is nonzero) or remove (if *argp is zero) the pseu-
            doterminal slave device.  (See also unlockpt(3).)
     TIOCGPTLCK     int *argp
            (since Linux 3.8) Place the current lock state of the pseudoter-
            minal slave device in the location pointed to by argp.
     TIOCGPTPEER    int flags
            (since  Linux 4.13) Given a file descriptor in fd that refers to
            a pseudoterminal master,  open  (with  the  given  open(2)-style
            flags)  and return a new file descriptor that refers to the peer
            pseudoterminal slave device.  This operation  can  be  performed
            regardless of whether the pathname of the slave device is acces-
            sible through the calling process's mount namespace.
            Security-conscious programs interacting with namespaces may wish
            to  use  this  operation  rather  than open(2) with the pathname
            returned by ptsname(3), and similar library functions that  have
            insecure  APIs.  (For example, confusion can occur in some cases
            using ptsname(3) with a pathname where a devpts  filesystem  has
            been mounted in a different mount namespace.)
     The BSD ioctls TIOCSTOP, TIOCSTART, TIOCUCNTL, TIOCREMOTE have not been
     implemented under Linux.
 Modem control
     TIOCMGET  int *argp
            Get the status of modem bits.
     TIOCMSET  const int *argp
            Set the status of modem bits.
     TIOCMBIC  const int *argp
            Clear the indicated modem bits.
     TIOCMBIS  const int *argp
            Set the indicated modem bits.
     The following bits are used by the above ioctls:
     TIOCM_LE        DSR (data set ready/line enable)
     TIOCM_DTR       DTR (data terminal ready)
     TIOCM_RTS       RTS (request to send)
     TIOCM_ST        Secondary TXD (transmit)
     TIOCM_SR        Secondary RXD (receive)
     TIOCM_CTS       CTS (clear to send)
     TIOCM_CAR       DCD (data carrier detect)
     TIOCM_CD         see TIOCM_CAR
     TIOCM_RNG       RNG (ring)
     TIOCM_RI         see TIOCM_RNG
     TIOCM_DSR       DSR (data set ready)
     TIOCMIWAIT     int arg
            Wait for any of the 4 modem bits (DCD, RI, DSR, CTS) to  change.
            The  bits  of  interest  are  specified as a bit mask in arg, by
            ORing together any of  the  bit  values,  TIOCM_RNG,  TIOCM_DSR,
            TIOCM_CD,  and  TIOCM_CTS.  The caller should use TIOCGICOUNT to
            see which bit has changed.
     TIOCGICOUNT    struct serial_icounter_struct *argp
            Get counts of input serial line interrupts (DCD, RI, DSR,  CTS).
            The  counts  are written to the serial_icounter_struct structure
            pointed to by argp.
            Note: both 1->0 and 0->1 transitions are counted, except for RI,
            where only 0->1 transitions are counted.
 Marking a line as local
     TIOCGSOFTCAR   int *argp
            ("Get  software carrier flag") Get the status of the CLOCAL flag
            in the c_cflag field of the termios structure.
     TIOCSSOFTCAR   const int *argp
            ("Set software carrier flag") Set the CLOCAL flag in the termios
            structure when *argp is nonzero, and clear it otherwise.
     If the CLOCAL flag for a line is off, the hardware carrier detect (DCD)
     signal is significant, and an open(2)  of  the  corresponding  terminal
     will  block until DCD is asserted, unless the O_NONBLOCK flag is given.
     If CLOCAL is set, the line behaves as if DCD is always  asserted.   The
     software  carrier  flag  is usually turned on for local devices, and is
     off for lines with modems.
 Linux-specific
     For the TIOCLINUX ioctl, see ioctl_console(2).
 Kernel debugging
     #include <linux/tty.h>
     TIOCTTYGSTRUCT struct tty_struct *argp
            Get the  tty_struct  corresponding  to  fd.   This  command  was
            removed in Linux 2.5.67.

RETURN VALUE

     The ioctl(2) system call returns 0 on success.  On error, it returns -1
     and sets errno appropriately.

ERRORS

     EINVAL Invalid command parameter.
     ENOIOCTLCMD
            Unknown command.
     ENOTTY Inappropriate fd.
     EPERM  Insufficient permission.

EXAMPLE

     Check the condition of DTR on the serial port.
     #include <termios.h> #include <fcntl.h> #include <sys/ioctl.h>
     int main(void) {
         int fd, serial;
         fd = open("/dev/ttyS0", O_RDONLY);
         ioctl(fd, TIOCMGET, &serial);
         if (serial & TIOCM_DTR)
             puts("TIOCM_DTR is set");
         else
             puts("TIOCM_DTR is not set");
         close(fd); }

SEE ALSO

     ldattach(1), ioctl(2), ioctl_console(2), termios(3), pty(7)

COLOPHON

     This page is part of release 4.16 of the Linux  man-pages  project.   A
     description  of  the project, information about reporting bugs, and the
     latest    version    of    this    page,    can     be     found     at
     https://www.kernel.org/doc/man-pages/.

Linux 2017-09-15 IOCTL_TTY(2)

/data/webs/external/dokuwiki/data/pages/man/tty_ioctl.txt · Last modified: 2019/05/17 09:32 by 127.0.0.1

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