mirror of https://github.com/mkerrisk/man-pages
778 lines
16 KiB
Groff
778 lines
16 KiB
Groff
.\" Copyright 2002 Walter Harms <walter.harms@informatik.uni-oldenburg.de>
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.\" and Andries Brouwer <aeb@cwi.nl>.
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.\"
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.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
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.\" Distributed under GPL
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.\" %%%LICENSE_END
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.\"
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.TH IOCTL_TTY 2 2021-08-27 "Linux" "Linux Programmer's Manual"
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.SH NAME
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ioctl_tty \- ioctls for terminals and serial lines
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.SH SYNOPSIS
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.nf
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.B #include <sys/ioctl.h>
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.BR "#include <termios.h>" " /* Definition of " CLOCAL ", and"
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.BR " TC*" { FLUSH , ON , OFF "} constants */"
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.PP
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.BI "int ioctl(int " fd ", int " cmd ", ...);"
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.fi
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.SH DESCRIPTION
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The
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.BR ioctl (2)
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call for terminals and serial ports accepts many possible command arguments.
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Most require a third argument, of varying type, here called
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.I argp
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or
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.IR arg .
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.PP
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Use of
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.BR ioctl ()
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makes for nonportable programs.
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Use the POSIX interface described in
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.BR termios (3)
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whenever possible.
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.SS Get and set terminal attributes
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.TP
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.B TCGETS
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Argument:
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.BI "struct termios *" argp
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.IP
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Equivalent to
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.IR "tcgetattr(fd, argp)" .
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.IP
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Get the current serial port settings.
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.TP
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.B TCSETS
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Argument:
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.BI "const struct termios *" argp
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.IP
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Equivalent to
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.IR "tcsetattr(fd, TCSANOW, argp)" .
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.IP
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Set the current serial port settings.
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.TP
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.B TCSETSW
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Argument:
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.BI "const struct termios *" argp
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.IP
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Equivalent to
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.IR "tcsetattr(fd, TCSADRAIN, argp)" .
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.IP
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Allow the output buffer to drain, and
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set the current serial port settings.
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.TP
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.B TCSETSF
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Argument:
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.BI "const struct termios *" argp
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.IP
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Equivalent to
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.IR "tcsetattr(fd, TCSAFLUSH, argp)" .
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.IP
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Allow the output buffer to drain, discard pending input, and
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set the current serial port settings.
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.PP
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The following four ioctls, added in Linux 2.6.20,
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.\" commit 64bb6c5e1ddcd47c951740485026ef08975ee2e6
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.\" commit 592ee3a5e5e2a981ef2829a0380093006d045661
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are just like
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.BR TCGETS ,
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.BR TCSETS ,
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.BR TCSETSW ,
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.BR TCSETSF ,
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except that they take a
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.I "struct termios2\ *"
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instead of a
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.IR "struct termios\ *" .
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If the structure member
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.B c_cflag
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contains the flag
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.BR BOTHER ,
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then the baud rate is stored in the structure members
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.B c_ispeed
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and
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.B c_ospeed
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as integer values.
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These ioctls are not supported on all architectures.
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.RS
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.TS
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lb l.
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TCGETS2 \fBstruct termios2 *\fPargp
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TCSETS2 \fBconst struct termios2 *\fPargp
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TCSETSW2 \fBconst struct termios2 *\fPargp
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TCSETSF2 \fBconst struct termios2 *\fPargp
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.TE
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.RE
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.PP
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The following four ioctls are just like
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.BR TCGETS ,
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.BR TCSETS ,
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.BR TCSETSW ,
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.BR TCSETSF ,
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except that they take a
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.I "struct termio\ *"
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instead of a
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.IR "struct termios\ *" .
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.RS
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.TS
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lb l.
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TCGETA \fBstruct termio *\fPargp
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TCSETA \fBconst struct termio *\fPargp
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TCSETAW \fBconst struct termio *\fPargp
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TCSETAF \fBconst struct termio *\fPargp
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.TE
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.RE
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.SS Locking the termios structure
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The
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.I termios
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structure of a terminal can be locked.
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The lock is itself a
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.I termios
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structure, with nonzero bits or fields indicating a
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locked value.
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.TP
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.B TIOCGLCKTRMIOS
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Argument:
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.BI "struct termios *" argp
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.IP
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Gets the locking status of the
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.I termios
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structure of the terminal.
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.TP
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.B TIOCSLCKTRMIOS
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Argument:
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.BI "const struct termios *" argp
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.IP
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Sets the locking status of the
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.I termios
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structure of the terminal.
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Only a process with the
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.BR CAP_SYS_ADMIN
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capability can do this.
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.SS Get and set window size
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Window sizes are kept in the kernel, but not used by the kernel
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(except in the case of virtual consoles, where the kernel will
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update the window size when the size of the virtual console changes,
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for example, by loading a new font).
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.TP
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.B TIOCGWINSZ
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Argument:
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.BI "struct winsize *" argp
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.IP
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Get window size.
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.TP
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.B TIOCSWINSZ
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Argument:
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.BI "const struct winsize *" argp
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.IP
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Set window size.
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.PP
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The struct used by these ioctls is defined as
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.PP
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.in +4n
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.EX
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struct winsize {
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unsigned short ws_row;
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unsigned short ws_col;
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unsigned short ws_xpixel; /* unused */
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unsigned short ws_ypixel; /* unused */
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};
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.EE
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.in
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.PP
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When the window size changes, a
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.B SIGWINCH
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signal is sent to the
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foreground process group.
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.SS Sending a break
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.TP
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.B TCSBRK
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Argument:
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.BI "int " arg
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.IP
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Equivalent to
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.IR "tcsendbreak(fd, arg)" .
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.IP
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If the terminal is using asynchronous serial data transmission, and
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.I arg
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is zero, then send a break (a stream of zero bits) for between
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0.25 and 0.5 seconds.
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If the terminal is not using asynchronous
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serial data transmission, then either a break is sent, or the function
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returns without doing anything.
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When
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.I arg
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is nonzero, nobody knows what will happen.
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.IP
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(SVr4, UnixWare, Solaris, and Linux treat
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.I "tcsendbreak(fd,arg)"
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with nonzero
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.I arg
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like
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.IR "tcdrain(fd)" .
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SunOS treats
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.I arg
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as a multiplier, and sends a stream of bits
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.I arg
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times as long as done for zero
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.IR arg .
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DG/UX and AIX treat
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.I arg
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(when nonzero) as a time interval measured in milliseconds.
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HP-UX ignores
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.IR arg .)
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.TP
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.B TCSBRKP
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Argument:
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.BI "int " arg
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.IP
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So-called "POSIX version" of
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.BR TCSBRK .
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It treats nonzero
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.I arg
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as a time interval measured in deciseconds, and does nothing
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when the driver does not support breaks.
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.TP
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.B TIOCSBRK
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Argument:
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.BI "void"
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.IP
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Turn break on, that is, start sending zero bits.
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.TP
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.B TIOCCBRK
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Argument:
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.BI "void"
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.IP
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Turn break off, that is, stop sending zero bits.
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.SS Software flow control
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.TP
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.B TCXONC
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Argument:
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.BI "int " arg
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.IP
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Equivalent to
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.IR "tcflow(fd, arg)" .
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.IP
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See
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.BR tcflow (3)
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for the argument values
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.BR TCOOFF ,
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.BR TCOON ,
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.BR TCIOFF ,
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.BR TCION .
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.SS Buffer count and flushing
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.TP
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.BI FIONREAD
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Argument:
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.BI "int *" argp
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.IP
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Get the number of bytes in the input buffer.
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.TP
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.B TIOCINQ
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Argument:
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.BI "int *" argp
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.IP
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Same as
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.BR FIONREAD .
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.TP
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.B TIOCOUTQ
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Argument:
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.BI "int *" argp
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.IP
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Get the number of bytes in the output buffer.
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.TP
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.B TCFLSH
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Argument:
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.BI "int " arg
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.IP
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Equivalent to
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.IR "tcflush(fd, arg)" .
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.IP
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See
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.BR tcflush (3)
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for the argument values
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.BR TCIFLUSH ,
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.BR TCOFLUSH ,
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.BR TCIOFLUSH .
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.SS Faking input
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.TP
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.B TIOCSTI
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Argument:
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.BI "const char *" argp
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.IP
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Insert the given byte in the input queue.
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.SS Redirecting console output
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.TP
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.B TIOCCONS
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Argument:
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.BI "void"
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.IP
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Redirect output that would have gone to
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.I /dev/console
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or
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.I /dev/tty0
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to the given terminal.
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If that was a pseudoterminal master, send it to the slave.
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In Linux before version 2.6.10,
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anybody can do this as long as the output was not redirected yet;
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since version 2.6.10, only a process with the
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.BR CAP_SYS_ADMIN
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capability may do this.
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If output was redirected already, then
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.B EBUSY
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is returned,
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but redirection can be stopped by using this ioctl with
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.I fd
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pointing at
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.I /dev/console
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or
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.IR /dev/tty0 .
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.SS Controlling terminal
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.TP
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.B TIOCSCTTY
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Argument:
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.BI "int " arg
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.IP
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Make the given terminal the controlling terminal of the calling process.
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The calling process must be a session leader and not have a
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controlling terminal already.
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For this case,
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.I arg
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should be specified as zero.
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.IP
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If this terminal is already the controlling terminal
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of a different session group, then the ioctl fails with
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.BR EPERM ,
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unless the caller has the
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.BR CAP_SYS_ADMIN
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capability and
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.I arg
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equals 1, in which case the terminal is stolen, and all processes that had
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it as controlling terminal lose it.
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.TP
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.B TIOCNOTTY
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Argument:
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.BI "void"
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.IP
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If the given terminal was the controlling terminal of the calling process,
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give up this controlling terminal.
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If the process was session leader,
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then send
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.B SIGHUP
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and
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.B SIGCONT
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to the foreground process group
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and all processes in the current session lose their controlling terminal.
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.SS Process group and session ID
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.TP
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.B TIOCGPGRP
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Argument:
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.BI "pid_t *" argp
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.IP
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When successful, equivalent to
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.IR "*argp = tcgetpgrp(fd)" .
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.IP
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Get the process group ID of the foreground process group on this terminal.
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.TP
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.B TIOCSPGRP
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Argument:
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.BI "const pid_t *" argp
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.IP
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Equivalent to
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.IR "tcsetpgrp(fd, *argp)" .
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.IP
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Set the foreground process group ID of this terminal.
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.TP
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.B TIOCGSID
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Argument:
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.BI "pid_t *" argp
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.IP
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When successful, equivalent to
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.IR "*argp = tcgetsid(fd)" .
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.IP
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Get the session ID of the given terminal.
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This fails with the error
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.B ENOTTY
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if the terminal is not a master pseudoterminal
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and not our controlling terminal.
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Strange.
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.SS Exclusive mode
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.TP
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.B TIOCEXCL
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Argument:
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.BI "void"
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.IP
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Put the terminal into exclusive mode.
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No further
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.BR open (2)
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operations on the terminal are permitted.
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(They fail with
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.BR EBUSY ,
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except for a process with the
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.BR CAP_SYS_ADMIN
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capability.)
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.TP
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.B TIOCGEXCL
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Argument:
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.BI "int *" argp
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.IP
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(since Linux 3.8)
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If the terminal is currently in exclusive mode,
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place a nonzero value in the location pointed to by
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.IR argp ;
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otherwise, place zero in
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.IR *argp .
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.TP
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.B TIOCNXCL
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Argument:
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.BI "void"
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.IP
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Disable exclusive mode.
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.SS Line discipline
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.TP
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.B TIOCGETD
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Argument:
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.BI "int *" argp
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.IP
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Get the line discipline of the terminal.
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.TP
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.B TIOCSETD
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Argument:
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.BI "const int *" argp
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.IP
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Set the line discipline of the terminal.
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.SS Pseudoterminal ioctls
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.TP
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.B TIOCPKT
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Argument:
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.BI "const int *" argp
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.IP
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Enable (when
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.RI * argp
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is nonzero) or disable packet mode.
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Can be applied to the master side of a pseudoterminal only (and will return
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.B ENOTTY
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otherwise).
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In packet mode, each subsequent
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.BR read (2)
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will return a packet that either contains a single nonzero control byte,
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or has a single byte containing zero (\(aq\e0\(aq) followed by data
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written on the slave side of the pseudoterminal.
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If the first byte is not
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.B TIOCPKT_DATA
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(0), it is an OR of one
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or more of the following bits:
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.IP
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.ad l
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.TS
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lb l.
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TIOCPKT_FLUSHREAD T{
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The read queue for the terminal is flushed.
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T}
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TIOCPKT_FLUSHWRITE T{
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The write queue for the terminal is flushed.
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T}
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TIOCPKT_STOP T{
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Output to the terminal is stopped.
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T}
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TIOCPKT_START T{
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Output to the terminal is restarted.
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T}
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TIOCPKT_DOSTOP T{
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The start and stop characters are \fB\(haS\fP/\fB\(haQ\fP.
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T}
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TIOCPKT_NOSTOP T{
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The start and stop characters are not \fB\(haS\fP/\fB\(haQ\fP.
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T}
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.TE
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.ad
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.IP
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While packet mode is in use, the presence
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of control status information to be read
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from the master side may be detected by a
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.BR select (2)
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for exceptional conditions or a
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.BR poll (2)
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for the
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.B POLLPRI
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event.
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.IP
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This mode is used by
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.BR rlogin (1)
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and
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.BR rlogind (8)
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to implement a remote-echoed,
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locally \fB\(haS\fP/\fB\(haQ\fP flow-controlled remote login.
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.TP
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.B TIOCGPKT
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Argument:
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.BI "const int *" argp
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.IP
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(since Linux 3.8)
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Return the current packet mode setting in the integer pointed to by
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.IR argp .
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.TP
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.B TIOCSPTLCK
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Argument:
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.BI "int *" argp
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.IP
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Set (if
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.IR *argp
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is nonzero) or remove (if
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.IR *argp
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is zero) the lock on the pseudoterminal slave device.
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(See also
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.BR unlockpt (3).)
|
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.TP
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.B TIOCGPTLCK
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Argument:
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.BI "int *" argp
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.IP
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(since Linux 3.8)
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Place the current lock state of the pseudoterminal slave device
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in the location pointed to by
|
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.IR argp .
|
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.TP
|
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.B TIOCGPTPEER
|
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Argument:
|
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.BI "int " flags
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.IP
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.\" commit 54ebbfb1603415d9953c150535850d30609ef077
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(since Linux 4.13)
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Given a file descriptor in
|
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.I fd
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that refers to a pseudoterminal master,
|
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open (with the given
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.BR open (2)-style
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.IR flags )
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and return a new file descriptor that refers to the peer
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pseudoterminal slave device.
|
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This operation can be performed
|
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regardless of whether the pathname of the slave device
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is accessible through the calling process's mount namespace.
|
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.IP
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Security-conscious programs interacting with namespaces may wish to use this
|
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operation rather than
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.BR open (2)
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with the pathname returned by
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.BR ptsname (3),
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and similar library functions that have insecure APIs.
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(For example, confusion can occur in some cases using
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.BR ptsname (3)
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with a pathname where a devpts filesystem
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has been mounted in a different mount namespace.)
|
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.PP
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The BSD ioctls
|
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.BR TIOCSTOP ,
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.BR TIOCSTART ,
|
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.BR TIOCUCNTL ,
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and
|
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.B TIOCREMOTE
|
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have not been implemented under Linux.
|
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.SS Modem control
|
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.TP
|
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.B TIOCMGET
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Argument:
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.BI "int *" argp
|
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.IP
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Get the status of modem bits.
|
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.TP
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.B TIOCMSET
|
|
Argument:
|
|
.BI "const int *" argp
|
|
.IP
|
|
Set the status of modem bits.
|
|
.TP
|
|
.B TIOCMBIC
|
|
Argument:
|
|
.BI "const int *" argp
|
|
.IP
|
|
Clear the indicated modem bits.
|
|
.TP
|
|
.B TIOCMBIS
|
|
Argument:
|
|
.BI "const int *" argp
|
|
.IP
|
|
Set the indicated modem bits.
|
|
.PP
|
|
The following bits are used by the above ioctls:
|
|
.PP
|
|
.TS
|
|
lb l.
|
|
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)
|
|
.TE
|
|
.TP
|
|
.B TIOCMIWAIT
|
|
Argument:
|
|
.BI "int " arg
|
|
.IP
|
|
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
|
|
.IR arg ,
|
|
by ORing together any of the bit values,
|
|
.BR TIOCM_RNG ,
|
|
.BR TIOCM_DSR ,
|
|
.BR TIOCM_CD ,
|
|
and
|
|
.BR TIOCM_CTS .
|
|
The caller should use
|
|
.B TIOCGICOUNT
|
|
to see which bit has changed.
|
|
.TP
|
|
.B TIOCGICOUNT
|
|
Argument:
|
|
.BI "struct serial_icounter_struct *" argp
|
|
.IP
|
|
Get counts of input serial line interrupts (DCD, RI, DSR, CTS).
|
|
The counts are written to the
|
|
.I serial_icounter_struct
|
|
structure pointed to by
|
|
.IR argp .
|
|
.IP
|
|
Note: both 1->0 and 0->1 transitions are counted, except for
|
|
RI, where only 0->1 transitions are counted.
|
|
.SS Marking a line as local
|
|
.TP
|
|
.B TIOCGSOFTCAR
|
|
Argument:
|
|
.BI "int *" argp
|
|
.IP
|
|
("Get software carrier flag")
|
|
Get the status of the CLOCAL flag in the c_cflag field of the
|
|
.I termios
|
|
structure.
|
|
.TP
|
|
.B TIOCSSOFTCAR
|
|
Argument:
|
|
.BI "const int *" argp
|
|
.IP
|
|
("Set software carrier flag")
|
|
Set the CLOCAL flag in the
|
|
.I termios
|
|
structure when
|
|
.RI * argp
|
|
is nonzero, and clear it otherwise.
|
|
.PP
|
|
If the
|
|
.B CLOCAL
|
|
flag for a line is off, the hardware carrier detect (DCD)
|
|
signal is significant, and an
|
|
.BR open (2)
|
|
of the corresponding terminal will block until DCD is asserted,
|
|
unless the
|
|
.B O_NONBLOCK
|
|
flag is given.
|
|
If
|
|
.B 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.
|
|
.SS Linux-specific
|
|
For the
|
|
.B TIOCLINUX
|
|
ioctl, see
|
|
.BR ioctl_console (2).
|
|
.SS Kernel debugging
|
|
.B "#include <linux/tty.h>"
|
|
.TP
|
|
.B TIOCTTYGSTRUCT
|
|
Argument:
|
|
.BI "struct tty_struct *" argp
|
|
.IP
|
|
Get the
|
|
.I tty_struct
|
|
corresponding to
|
|
.IR fd .
|
|
This command was removed in Linux 2.5.67.
|
|
.\" commit b3506a09d15dc5aee6d4bb88d759b157016e1864
|
|
.\" Author: Andries E. Brouwer <andries.brouwer@cwi.nl>
|
|
.\" Date: Tue Apr 1 04:42:46 2003 -0800
|
|
.\"
|
|
.\" [PATCH] kill TIOCTTYGSTRUCT
|
|
.\"
|
|
.\" Only used for (dubious) debugging purposes, and exposes
|
|
.\" internal kernel state.
|
|
.\"
|
|
.\" .SS Serial info
|
|
.\" .BR "#include <linux/serial.h>"
|
|
.\" .PP
|
|
.\" .TP
|
|
.\" .BI "TIOCGSERIAL struct serial_struct *" argp
|
|
.\" Get serial info.
|
|
.\" .TP
|
|
.\" .BI "TIOCSSERIAL const struct serial_struct *" argp
|
|
.\" Set serial info.
|
|
.SH RETURN VALUE
|
|
The
|
|
.BR ioctl (2)
|
|
system call returns 0 on success.
|
|
On error, it returns \-1 and sets
|
|
.I errno
|
|
to indicate the error.
|
|
.SH ERRORS
|
|
.TP
|
|
.B EINVAL
|
|
Invalid command parameter.
|
|
.TP
|
|
.B ENOIOCTLCMD
|
|
Unknown command.
|
|
.TP
|
|
.B ENOTTY
|
|
Inappropriate
|
|
.IR fd .
|
|
.TP
|
|
.B EPERM
|
|
Insufficient permission.
|
|
.SH EXAMPLES
|
|
Check the condition of DTR on the serial port.
|
|
.PP
|
|
.EX
|
|
#include <stdio.h>
|
|
#include <unistd.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);
|
|
}
|
|
.EE
|
|
.SH SEE ALSO
|
|
.BR ldattach (1),
|
|
.BR ioctl (2),
|
|
.BR ioctl_console (2),
|
|
.BR termios (3),
|
|
.BR pty (7)
|
|
.\"
|
|
.\" FIONBIO const int *
|
|
.\" FIONCLEX void
|
|
.\" FIOCLEX void
|
|
.\" FIOASYNC const int *
|
|
.\" from serial.c:
|
|
.\" TIOCSERCONFIG void
|
|
.\" TIOCSERGWILD int *
|
|
.\" TIOCSERSWILD const int *
|
|
.\" TIOCSERGSTRUCT struct async_struct *
|
|
.\" TIOCSERGETLSR int *
|
|
.\" TIOCSERGETMULTI struct serial_multiport_struct *
|
|
.\" TIOCSERSETMULTI const struct serial_multiport_struct *
|
|
.\" TIOCGSERIAL, TIOCSSERIAL (see above)
|