Merging upstream version 6.8.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1235 insertions, 0 deletions

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+'\" t
+.\" Copyright (c) 1993 Michael Haardt (michael@moria.de)
+.\" Fri Apr  2 11:32:09 MET DST 1993
+.\" Copyright (c) 2006-2015, Michael Kerrisk <mtk.manpages@gmail.com>
+.\"
+.\" SPDX-License-Identifier: GPL-2.0-or-later
+.\"
+.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
+.\" Modified 1995-02-25 by Jim Van Zandt <jrv@vanzandt.mv.com>
+.\" Modified 1995-09-02 by Jim Van Zandt <jrv@vanzandt.mv.com>
+.\" moved to man3, aeb, 950919
+.\" Modified 2001-09-22 by Michael Kerrisk <mtk.manpages@gmail.com>
+.\" Modified 2001-12-17, aeb
+.\" Modified 2004-10-31, aeb
+.\" 2006-12-28, mtk:
+.\"     Added .SS headers to give some structure to this page; and a
+.\"     small amount of reordering.
+.\"     Added a section on canonical and noncanonical mode.
+.\"     Enhanced the discussion of "raw" mode for cfmakeraw().
+.\"     Document CMSPAR.
+.\"
+.TH termios 3 2024-05-02 "Linux man-pages (unreleased)"
+.SH NAME
+termios, tcgetattr, tcsetattr, tcsendbreak, tcdrain, tcflush, tcflow,
+cfmakeraw, cfgetospeed, cfgetispeed, cfsetispeed, cfsetospeed, cfsetspeed \-
+get and set terminal attributes, line control, get and set baud rate
+.SH LIBRARY
+Standard C library
+.RI ( libc ", " \-lc )
+.SH SYNOPSIS
+.nf
+.B #include <termios.h>
+.B #include <unistd.h>
+.P
+.BI "int tcgetattr(int " fd ", struct termios *" termios_p );
+.BI "int tcsetattr(int " fd ", int " optional_actions ,
+.BI "              const struct termios *" termios_p );
+.P
+.BI "int tcsendbreak(int " fd ", int " duration );
+.BI "int tcdrain(int " fd );
+.BI "int tcflush(int " fd ", int " queue_selector );
+.BI "int tcflow(int " fd ", int " action );
+.P
+.BI "void cfmakeraw(struct termios *" termios_p );
+.P
+.BI "speed_t cfgetispeed(const struct termios *" termios_p );
+.BI "speed_t cfgetospeed(const struct termios *" termios_p );
+.P
+.BI "int cfsetispeed(struct termios *" termios_p ", speed_t " speed );
+.BI "int cfsetospeed(struct termios *" termios_p ", speed_t " speed );
+.BI "int cfsetspeed(struct termios *" termios_p ", speed_t " speed );
+.fi
+.P
+.RS -4
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.RE
+.P
+.BR cfsetspeed (),
+.BR cfmakeraw ():
+.nf
+    Since glibc 2.19:
+        _DEFAULT_SOURCE
+    glibc 2.19 and earlier:
+        _BSD_SOURCE
+.fi
+.SH DESCRIPTION
+The termios functions describe a general terminal interface that is
+provided to control asynchronous communications ports.
+.SS The termios structure
+Many of the functions described here have a \fItermios_p\fP argument
+that is a pointer to a \fItermios\fP structure.
+This structure contains at least the following members:
+.P
+.in +4n
+.EX
+tcflag_t c_iflag;      /* input modes */
+tcflag_t c_oflag;      /* output modes */
+tcflag_t c_cflag;      /* control modes */
+tcflag_t c_lflag;      /* local modes */
+cc_t     c_cc[NCCS];   /* special characters */
+.EE
+.in
+.P
+The values that may be assigned to these fields are described below.
+In the case of the first four bit-mask fields,
+the definitions of some of the associated flags that may be set are
+exposed only if a specific feature test macro (see
+.BR feature_test_macros (7))
+is defined, as noted in brackets ("[]").
+.P
+In the descriptions below, "not in POSIX" means that the
+value is not specified in POSIX.1-2001,
+and "XSI" means that the value is specified in POSIX.1-2001
+as part of the XSI extension.
+.P
+\fIc_iflag\fP flag constants:
+.TP
+.B IGNBRK
+Ignore BREAK condition on input.
+.TP
+.B BRKINT
+If \fBIGNBRK\fP is set, a BREAK is ignored.
+If it is not set
+but \fBBRKINT\fP is set, then a BREAK causes the input and output
+queues to be flushed, and if the terminal is the controlling
+terminal of a foreground process group, it will cause a
+\fBSIGINT\fP to be sent to this foreground process group.
+When neither \fBIGNBRK\fP nor \fBBRKINT\fP are set, a BREAK
+reads as a null byte (\[aq]\e0\[aq]), except when \fBPARMRK\fP is set,
+in which case it reads as the sequence \e377 \e0 \e0.
+.TP
+.B IGNPAR
+Ignore framing errors and parity errors.
+.TP
+.B PARMRK
+If this bit is set, input bytes with parity or framing errors are
+marked when passed to the program.
+This bit is meaningful only when
+\fBINPCK\fP is set and \fBIGNPAR\fP is not set.
+The way erroneous bytes are marked is with two preceding bytes,
+\e377 and \e0.
+Thus, the program actually reads three bytes for one
+erroneous byte received from the terminal.
+If a valid byte has the value \e377,
+and \fBISTRIP\fP (see below) is not set,
+the program might confuse it with the prefix that marks a
+parity error.
+Therefore, a valid byte \e377 is passed to the program as two
+bytes, \e377 \e377, in this case.
+.IP
+If neither \fBIGNPAR\fP nor \fBPARMRK\fP
+is set, read a character with a parity error or framing error
+as \e0.
+.TP
+.B INPCK
+Enable input parity checking.
+.TP
+.B ISTRIP
+Strip off eighth bit.
+.TP
+.B INLCR
+Translate NL to CR on input.
+.TP
+.B IGNCR
+Ignore carriage return on input.
+.TP
+.B ICRNL
+Translate carriage return to newline on input (unless \fBIGNCR\fP is set).
+.TP
+.B IUCLC
+(not in POSIX) Map uppercase characters to lowercase on input.
+.TP
+.B IXON
+Enable XON/XOFF flow control on output.
+.TP
+.B IXANY
+(XSI) Typing any character will restart stopped output.
+(The default is to allow just the START character to restart output.)
+.TP
+.B IXOFF
+Enable XON/XOFF flow control on input.
+.TP
+.B IMAXBEL
+(not in POSIX) Ring bell when input queue is full.
+Linux does not implement this bit, and acts as if it is always set.
+.TP
+.BR IUTF8 " (since Linux 2.6.4)"
+(not in POSIX) Input is UTF8;
+this allows character-erase to be correctly performed in cooked mode.
+.P
+.I c_oflag
+flag constants:
+.TP
+.B OPOST
+Enable implementation-defined output processing.
+.TP
+.B OLCUC
+(not in POSIX) Map lowercase characters to uppercase on output.
+.TP
+.B ONLCR
+(XSI) Map NL to CR-NL on output.
+.TP
+.B OCRNL
+Map CR to NL on output.
+.TP
+.B ONOCR
+Don't output CR at column 0.
+.TP
+.B ONLRET
+The NL character is assumed to do the carriage-return function;
+the kernel's idea of the current column is set to 0
+after both NL and CR.
+.TP
+.B OFILL
+Send fill characters for a delay, rather than using a timed delay.
+.TP
+.B OFDEL
+Fill character is ASCII DEL (0177).
+If unset, fill character is ASCII NUL (\[aq]\e0\[aq]).
+(Not implemented on Linux.)
+.TP
+.B NLDLY
+Newline delay mask.
+Values are \fBNL0\fP and \fBNL1\fP.
+[requires
+.B _BSD_SOURCE
+or
+.B _SVID_SOURCE
+or
+.BR _XOPEN_SOURCE ]
+.TP
+.B CRDLY
+Carriage return delay mask.
+Values are \fBCR0\fP, \fBCR1\fP, \fBCR2\fP, or \fBCR3\fP.
+[requires
+.B _BSD_SOURCE
+or
+.B _SVID_SOURCE
+or
+.BR _XOPEN_SOURCE ]
+.TP
+.B TABDLY
+Horizontal tab delay mask.
+Values are \fBTAB0\fP, \fBTAB1\fP, \fBTAB2\fP, \fBTAB3\fP (or \fBXTABS\fP,
+but see the
+.B BUGS
+section).
+A value of TAB3, that is, XTABS, expands tabs to spaces
+(with tab stops every eight columns).
+[requires
+.B _BSD_SOURCE
+or
+.B _SVID_SOURCE
+or
+.BR _XOPEN_SOURCE ]
+.TP
+.B BSDLY
+Backspace delay mask.
+Values are \fBBS0\fP or \fBBS1\fP.
+(Has never been implemented.)
+[requires
+.B _BSD_SOURCE
+or
+.B _SVID_SOURCE
+or
+.BR _XOPEN_SOURCE ]
+.TP
+.B VTDLY
+Vertical tab delay mask.
+Values are \fBVT0\fP or \fBVT1\fP.
+.TP
+.B FFDLY
+Form feed delay mask.
+Values are \fBFF0\fP or \fBFF1\fP.
+[requires
+.B _BSD_SOURCE
+or
+.B _SVID_SOURCE
+or
+.BR _XOPEN_SOURCE ]
+.P
+\fIc_cflag\fP flag constants:
+.TP
+.B CBAUD
+(not in POSIX) Baud speed mask (4+1 bits).
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+.TP
+.B CBAUDEX
+(not in POSIX) Extra baud speed mask (1 bit), included in
+.BR CBAUD .
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+.IP
+(POSIX says that the baud speed is stored in the
+.I termios
+structure without specifying where precisely, and provides
+.BR cfgetispeed ()
+and
+.BR cfsetispeed ()
+for getting at it.
+Some systems use bits selected by
+.B CBAUD
+in
+.IR c_cflag ,
+other systems use separate fields, for example,
+.I sg_ispeed
+and
+.IR sg_ospeed .)
+.TP
+.B CSIZE
+Character size mask.
+Values are \fBCS5\fP, \fBCS6\fP, \fBCS7\fP, or \fBCS8\fP.
+.TP
+.B CSTOPB
+Set two stop bits, rather than one.
+.TP
+.B CREAD
+Enable receiver.
+.TP
+.B PARENB
+Enable parity generation on output and parity checking for input.
+.TP
+.B PARODD
+If set, then parity for input and output is odd;
+otherwise even parity is used.
+.TP
+.B HUPCL
+Lower modem control lines after last process closes the device (hang up).
+.TP
+.B CLOCAL
+Ignore modem control lines.
+.TP
+.B LOBLK
+(not in POSIX) Block output from a noncurrent shell layer.
+For use by \fBshl\fP (shell layers).
+(Not implemented on Linux.)
+.TP
+.B CIBAUD
+(not in POSIX) Mask for input speeds.
+The values for the
+.B CIBAUD
+bits are
+the same as the values for the
+.B CBAUD
+bits, shifted left
+.B IBSHIFT
+bits.
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+(Not implemented in glibc, supported on Linux via
+.BR TCGET *
+and
+.BR TCSET *
+ioctls; see
+.BR ioctl_tty (2))
+.TP
+.B CMSPAR
+(not in POSIX)
+Use "stick" (mark/space) parity (supported on certain serial
+devices): if
+.B PARODD
+is set, the parity bit is always 1; if
+.B PARODD
+is not set, then the parity bit is always 0.
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+.TP
+.B CRTSCTS
+(not in POSIX) Enable RTS/CTS (hardware) flow control.
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+.P
+\fIc_lflag\fP flag constants:
+.TP
+.B ISIG
+When any of the characters INTR, QUIT, SUSP, or DSUSP are received,
+generate the corresponding signal.
+.TP
+.B ICANON
+Enable canonical mode (described below).
+.TP
+.B XCASE
+(not in POSIX; not supported under Linux)
+If \fBICANON\fP is also set, terminal is uppercase only.
+Input is converted to lowercase, except for characters preceded by \e.
+On output, uppercase characters are preceded by \e and lowercase
+characters are converted to uppercase.
+[requires
+.B _BSD_SOURCE
+or
+.B _SVID_SOURCE
+or
+.BR _XOPEN_SOURCE ]
+.\" glibc is probably now wrong to allow
+.\" Define
+.\" .B _XOPEN_SOURCE
+.\" to expose
+.\" .BR XCASE .
+.TP
+.B ECHO
+Echo input characters.
+.TP
+.B ECHOE
+If \fBICANON\fP is also set, the ERASE character erases the preceding
+input character, and WERASE erases the preceding word.
+.TP
+.B ECHOK
+If \fBICANON\fP is also set, the KILL character erases the current line.
+.TP
+.B ECHONL
+If \fBICANON\fP is also set, echo the NL character even if ECHO is not set.
+.TP
+.B ECHOCTL
+(not in POSIX) If \fBECHO\fP is also set,
+terminal special characters other than
+TAB, NL, START, and STOP are echoed as \fB\[ha]X\fP,
+where X is the character with
+ASCII code 0x40 greater than the special character.
+For example, character
+0x08 (BS) is echoed as \fB\[ha]H\fP.
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+.TP
+.B ECHOPRT
+(not in POSIX) If \fBICANON\fP and \fBECHO\fP are also set, characters
+are printed as they are being erased.
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+.TP
+.B ECHOKE
+(not in POSIX) If \fBICANON\fP is also set, KILL is echoed by erasing
+each character on the line, as specified by \fBECHOE\fP and \fBECHOPRT\fP.
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+.TP
+.B DEFECHO
+(not in POSIX) Echo only when a process is reading.
+(Not implemented on Linux.)
+.TP
+.B FLUSHO
+(not in POSIX; not supported under Linux)
+Output is being flushed.
+This flag is toggled by typing
+the DISCARD character.
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+.TP
+.B NOFLSH
+Disable flushing the input and output queues when generating signals for the
+INT, QUIT, and SUSP characters.
+.\" Stevens lets SUSP only flush the input queue
+.TP
+.B TOSTOP
+Send the
+.B SIGTTOU
+signal to the process group of a background process
+which tries to write to its controlling terminal.
+.TP
+.B PENDIN
+(not in POSIX; not supported under Linux)
+All characters in the input queue are reprinted when
+the next character is read.
+.RB ( bash (1)
+handles typeahead this way.)
+[requires
+.B _BSD_SOURCE
+or
+.BR _SVID_SOURCE ]
+.TP
+.B IEXTEN
+Enable implementation-defined input processing.
+This flag, as well as \fBICANON\fP must be enabled for the
+special characters EOL2, LNEXT, REPRINT, WERASE to be interpreted,
+and for the \fBIUCLC\fP flag to be effective.
+.P
+The \fIc_cc\fP array defines the terminal special characters.
+The symbolic indices (initial values) and meaning are:
+.TP
+.B VDISCARD
+(not in POSIX; not supported under Linux; 017, SI, Ctrl-O)
+Toggle: start/stop discarding pending output.
+Recognized when
+.B IEXTEN
+is set, and then not passed as input.
+.TP
+.B VDSUSP
+(not in POSIX; not supported under Linux; 031, EM, Ctrl-Y)
+Delayed suspend character (DSUSP):
+send
+.B SIGTSTP
+signal when the character is read by the user program.
+Recognized when
+.B IEXTEN
+and
+.B ISIG
+are set, and the system supports
+job control, and then not passed as input.
+.TP
+.B VEOF
+(004, EOT, Ctrl-D)
+End-of-file character (EOF).
+More precisely: this character causes the pending tty buffer to be sent
+to the waiting user program without waiting for end-of-line.
+If it is the first character of the line, the
+.BR read (2)
+in the user program returns 0, which signifies end-of-file.
+Recognized when
+.B ICANON
+is set, and then not passed as input.
+.TP
+.B VEOL
+(0, NUL)
+Additional end-of-line character (EOL).
+Recognized when
+.B ICANON
+is set.
+.TP
+.B VEOL2
+(not in POSIX; 0, NUL)
+Yet another end-of-line character (EOL2).
+Recognized when
+.B ICANON
+is set.
+.TP
+.B VERASE
+(0177, DEL, rubout, or 010, BS, Ctrl-H, or also #)
+Erase character (ERASE).
+This erases the previous not-yet-erased character,
+but does not erase past EOF or beginning-of-line.
+Recognized when
+.B ICANON
+is set, and then not passed as input.
+.TP
+.B VINTR
+(003, ETX, Ctrl-C, or also 0177, DEL, rubout)
+Interrupt character (INTR).
+Send a
+.B SIGINT
+signal.
+Recognized when
+.B ISIG
+is set, and then not passed as input.
+.TP
+.B VKILL
+(025, NAK, Ctrl-U, or Ctrl-X, or also @)
+Kill character (KILL).
+This erases the input since the last EOF or beginning-of-line.
+Recognized when
+.B ICANON
+is set, and then not passed as input.
+.TP
+.B VLNEXT
+(not in POSIX; 026, SYN, Ctrl-V)
+Literal next (LNEXT).
+Quotes the next input character, depriving it of
+a possible special meaning.
+Recognized when
+.B IEXTEN
+is set, and then not passed as input.
+.TP
+.B VMIN
+Minimum number of characters for noncanonical read (MIN).
+.TP
+.B VQUIT
+(034, FS, Ctrl-\e)
+Quit character (QUIT).
+Send
+.B SIGQUIT
+signal.
+Recognized when
+.B ISIG
+is set, and then not passed as input.
+.TP
+.B VREPRINT
+(not in POSIX; 022, DC2, Ctrl-R)
+Reprint unread characters (REPRINT).
+Recognized when
+.B ICANON
+and
+.B IEXTEN
+are set, and then not passed as input.
+.TP
+.B VSTART
+(021, DC1, Ctrl-Q)
+Start character (START).
+Restarts output stopped by the Stop character.
+Recognized when
+.B IXON
+is set, and then not passed as input.
+.TP
+.B VSTATUS
+(not in POSIX; not supported under Linux;
+status request: 024, DC4, Ctrl-T).
+Status character (STATUS).
+Display status information at terminal,
+including state of foreground process and amount of CPU time it has consumed.
+Also sends a
+.B SIGINFO
+signal (not supported on Linux) to the foreground process group.
+.TP
+.B VSTOP
+(023, DC3, Ctrl-S)
+Stop character (STOP).
+Stop output until Start character typed.
+Recognized when
+.B IXON
+is set, and then not passed as input.
+.TP
+.B VSUSP
+(032, SUB, Ctrl-Z)
+Suspend character (SUSP).
+Send
+.B SIGTSTP
+signal.
+Recognized when
+.B ISIG
+is set, and then not passed as input.
+.TP
+.B VSWTCH
+(not in POSIX; not supported under Linux; 0, NUL)
+Switch character (SWTCH).
+Used in System V to switch shells in
+.IR "shell layers" ,
+a predecessor to shell job control.
+.TP
+.B VTIME
+Timeout in deciseconds for noncanonical read (TIME).
+.TP
+.B VWERASE
+(not in POSIX; 027, ETB, Ctrl-W)
+Word erase (WERASE).
+Recognized when
+.B ICANON
+and
+.B IEXTEN
+are set, and then not passed as input.
+.P
+An individual terminal special character can be disabled by setting
+the value of the corresponding
+.I c_cc
+element to
+.BR _POSIX_VDISABLE .
+.P
+The above symbolic subscript values are all different, except that
+.BR VTIME ,
+.B VMIN
+may have the same value as
+.BR VEOL ,
+.BR VEOF ,
+respectively.
+In noncanonical mode the special character meaning is replaced
+by the timeout meaning.
+For an explanation of
+.B VMIN
+and
+.BR VTIME ,
+see the description of
+noncanonical mode below.
+.SS Retrieving and changing terminal settings
+.BR tcgetattr ()
+gets the parameters associated with the object referred by \fIfd\fP and
+stores them in the \fItermios\fP structure referenced by
+\fItermios_p\fP.
+This function may be invoked from a background process;
+however, the terminal attributes may be subsequently changed by a
+foreground process.
+.P
+.BR tcsetattr ()
+sets the parameters associated with the terminal (unless support is
+required from the underlying hardware that is not available) from the
+\fItermios\fP structure referred to by \fItermios_p\fP.
+\fIoptional_actions\fP specifies when the changes take effect:
+.TP
+.B TCSANOW
+the change occurs immediately.
+.TP
+.B TCSADRAIN
+the change occurs after all output written to
+.I fd
+has been transmitted.
+This option should be used when changing
+parameters that affect output.
+.TP
+.B TCSAFLUSH
+the change occurs after all output written to the object referred by
+.I fd
+has been transmitted, and all input that has been received but not read
+will be discarded before the change is made.
+.SS Canonical and noncanonical mode
+The setting of the
+.B ICANON
+canon flag in
+.I c_lflag
+determines whether the terminal is operating in canonical mode
+.RB ( ICANON
+set) or
+noncanonical mode
+.RB ( ICANON
+unset).
+By default,
+.B ICANON
+is set.
+.P
+In canonical mode:
+.IP \[bu] 3
+Input is made available line by line.
+An input line is available when one of the line delimiters
+is typed (NL, EOL, EOL2; or EOF at the start of line).
+Except in the case of EOF, the line delimiter is included
+in the buffer returned by
+.BR read (2).
+.IP \[bu]
+Line editing is enabled (ERASE, KILL;
+and if the
+.B IEXTEN
+flag is set: WERASE, REPRINT, LNEXT).
+A
+.BR read (2)
+returns at most one line of input; if the
+.BR read (2)
+requested fewer bytes than are available in the current line of input,
+then only as many bytes as requested are read,
+and the remaining characters will be available for a future
+.BR read (2).
+.IP \[bu]
+The maximum line length is 4096 chars
+(including the terminating newline character);
+lines longer than 4096 chars are truncated.
+After 4095 characters, input processing (e.g.,
+.B ISIG
+and
+.B ECHO*
+processing) continues, but any input data after 4095 characters up to
+(but not including) any terminating newline is discarded.
+This ensures that the terminal can always receive
+more input until at least one line can be read.
+.P
+In noncanonical mode input is available immediately (without
+the user having to type a line-delimiter character),
+no input processing is performed,
+and line editing is disabled.
+The read buffer will only accept 4095 chars; this provides the
+necessary space for a newline char if the input mode is switched
+to canonical.
+The settings of MIN
+.RI ( c_cc[VMIN] )
+and TIME
+.RI ( c_cc[VTIME] )
+determine the circumstances in which a
+.BR read (2)
+completes; there are four distinct cases:
+.TP
+MIN == 0, TIME == 0 (polling read)
+If data is available,
+.BR read (2)
+returns immediately, with the lesser of the number of bytes
+available, or the number of bytes requested.
+If no data is available,
+.BR read (2)
+returns 0.
+.TP
+MIN > 0, TIME == 0 (blocking read)
+.BR read (2)
+blocks until MIN bytes are available,
+and returns up to the number of bytes requested.
+.TP
+MIN == 0, TIME > 0 (read with timeout)
+TIME specifies the limit for a timer in tenths of a second.
+The timer is started when
+.BR read (2)
+is called.
+.BR read (2)
+returns either when at least one byte of data is available,
+or when the timer expires.
+If the timer expires without any input becoming available,
+.BR read (2)
+returns 0.
+If data is already available at the time of the call to
+.BR read (2),
+the call behaves as though the data was received immediately after the call.
+.TP
+MIN > 0, TIME > 0 (read with interbyte timeout)
+TIME specifies the limit for a timer in tenths of a second.
+Once an initial byte of input becomes available,
+the timer is restarted after each further byte is received.
+.BR read (2)
+returns when any of the following conditions is met:
+.RS
+.IP \[bu] 3
+MIN bytes have been received.
+.IP \[bu]
+The interbyte timer expires.
+.IP \[bu]
+The number of bytes requested by
+.BR read (2)
+has been received.
+(POSIX does not specify this termination condition,
+and on some other implementations
+.\" e.g., Solaris
+.BR read (2)
+does not return in this case.)
+.RE
+.IP
+Because the timer is started only after the initial byte
+becomes available, at least one byte will be read.
+If data is already available at the time of the call to
+.BR read (2),
+the call behaves as though the data was received immediately after the call.
+.P
+POSIX
+.\" POSIX.1-2008 XBD 11.1.7
+does not specify whether the setting of the
+.B O_NONBLOCK
+file status flag takes precedence over the MIN and TIME settings.
+If
+.B O_NONBLOCK
+is set, a
+.BR read (2)
+in noncanonical mode may return immediately,
+regardless of the setting of MIN or TIME.
+Furthermore, if no data is available,
+POSIX permits a
+.BR read (2)
+in noncanonical mode to return either 0, or \-1 with
+.I errno
+set to
+.BR EAGAIN .
+.SS Raw mode
+.BR cfmakeraw ()
+sets the terminal to something like the
+"raw" mode of the old Version 7 terminal driver:
+input is available character by character,
+echoing is disabled, and all special processing of
+terminal input and output characters is disabled.
+The terminal attributes are set as follows:
+.P
+.in +4n
+.EX
+termios_p\->c_iflag &= \[ti](IGNBRK | BRKINT | PARMRK | ISTRIP
+                | INLCR | IGNCR | ICRNL | IXON);
+termios_p\->c_oflag &= \[ti]OPOST;
+termios_p\->c_lflag &= \[ti](ECHO | ECHONL | ICANON | ISIG | IEXTEN);
+termios_p\->c_cflag &= \[ti](CSIZE | PARENB);
+termios_p\->c_cflag |= CS8;
+.EE
+.in
+.\"
+.SS Line control
+.BR tcsendbreak ()
+transmits a continuous stream of zero-valued bits for a specific
+duration, if the terminal is using asynchronous serial data
+transmission.
+If \fIduration\fP is zero, it transmits zero-valued bits
+for at least 0.25 seconds, and not more than 0.5 seconds.
+If \fIduration\fP is not zero, it sends zero-valued bits for some
+implementation-defined length of time.
+.P
+If the terminal is not using asynchronous serial data transmission,
+.BR tcsendbreak ()
+returns without taking any action.
+.P
+.BR tcdrain ()
+waits until all output written to the object referred to by
+.I fd
+has been transmitted.
+.P
+.BR tcflush ()
+discards data written to the object referred to by
+.I fd
+but not transmitted, or data received but not read, depending on the
+value of
+.IR queue_selector :
+.TP
+.B TCIFLUSH
+flushes data received but not read.
+.TP
+.B TCOFLUSH
+flushes data written but not transmitted.
+.TP
+.B TCIOFLUSH
+flushes both data received but not read, and data written but not
+transmitted.
+.P
+.BR tcflow ()
+suspends transmission or reception of data on the object referred to by
+.IR fd ,
+depending on the value of
+.IR action :
+.TP
+.B TCOOFF
+suspends output.
+.TP
+.B TCOON
+restarts suspended output.
+.TP
+.B TCIOFF
+transmits a STOP character, which stops the terminal device from
+transmitting data to the system.
+.TP
+.B TCION
+transmits a START character, which starts the terminal device
+transmitting data to the system.
+.P
+The default on open of a terminal file is that neither its input nor its
+output is suspended.
+.SS Line speed
+The baud rate functions are provided for getting and setting the values
+of the input and output baud rates in the \fItermios\fP structure.
+The new values do not take effect
+until
+.BR tcsetattr ()
+is successfully called.
+.P
+Setting the speed to \fBB0\fP instructs the modem to "hang up".
+The actual bit rate corresponding to \fBB38400\fP may be altered with
+.BR setserial (8).
+.P
+The input and output baud rates are stored in the \fItermios\fP
+structure.
+.P
+.BR cfgetospeed ()
+returns the output baud rate stored in the \fItermios\fP structure
+pointed to by
+.IR termios_p .
+.P
+.BR cfsetospeed ()
+sets the output baud rate stored in the \fItermios\fP structure pointed
+to by \fItermios_p\fP to \fIspeed\fP, which must be one of these constants:
+.RS
+.TP
+.B B0
+.TQ
+.B B50
+.TQ
+.B B75
+.TQ
+.B B110
+.TQ
+.B B134
+.TQ
+.B B150
+.TQ
+.B B200
+.TQ
+.B B300
+.TQ
+.B B600
+.TQ
+.B B1200
+.TQ
+.B B1800
+.TQ
+.B B2400
+.TQ
+.B B4800
+.TQ
+.B B9600
+.TQ
+.B B19200
+.TQ
+.B B38400
+.TQ
+.B B57600
+.TQ
+.B B115200
+.TQ
+.B B230400
+.TQ
+.B B460800
+.TQ
+.B B500000
+.TQ
+.B B576000
+.TQ
+.B B921600
+.TQ
+.B B1000000
+.TQ
+.B B1152000
+.TQ
+.B B1500000
+.TQ
+.B B2000000
+.RE
+.P
+These constants are additionally supported on the SPARC architecture:
+.RS
+.TP
+.B B76800
+.TQ
+.B B153600
+.TQ
+.B B307200
+.TQ
+.B B614400
+.RE
+.P
+These constants are additionally supported on non-SPARC architectures:
+.RS
+.TP
+.B B2500000
+.TQ
+.B B3000000
+.TQ
+.B B3500000
+.TQ
+.B B4000000
+.RE
+.P
+Due to differences between architectures, portable applications should check
+if a particular
+.BI B nnn
+constant is defined prior to using it.
+.P
+The zero baud rate,
+.BR B0 ,
+is used to terminate the connection.
+If
+.B B0
+is specified, the modem control lines shall no longer be asserted.
+Normally, this will disconnect the line.
+.B CBAUDEX
+is a mask
+for the speeds beyond those defined in POSIX.1 (57600 and above).
+Thus,
+.BR B57600 " & " CBAUDEX
+is nonzero.
+.P
+Setting the baud rate to a value other than those defined by
+.BI B nnn
+constants is possible via the
+.B TCSETS2
+ioctl; see
+.BR ioctl_tty (2).
+.P
+.BR cfgetispeed ()
+returns the input baud rate stored in the
+.I termios
+structure.
+.P
+.BR cfsetispeed ()
+sets the input baud rate stored in the
+.I termios
+structure to
+.IR speed ,
+which must be specified as one of the
+.BI B nnn
+constants listed above for
+.BR cfsetospeed ().
+If the input baud rate is set to the literal constant
+.B 0
+(not the symbolic constant
+.BR B0 ),
+the input baud rate will be
+equal to the output baud rate.
+.P
+.BR cfsetspeed ()
+is a 4.4BSD extension.
+It takes the same arguments as
+.BR cfsetispeed (),
+and sets both input and output speed.
+.SH RETURN VALUE
+.BR cfgetispeed ()
+returns the input baud rate stored in the
+\fItermios\fP
+structure.
+.P
+.BR cfgetospeed ()
+returns the output baud rate stored in the \fItermios\fP structure.
+.P
+All other functions return:
+.TP
+.B 0
+on success.
+.TP
+.B \-1
+on failure and set
+.I errno
+to indicate the error.
+.P
+Note that
+.BR tcsetattr ()
+returns success if \fIany\fP of the requested changes could be
+successfully carried out.
+Therefore, when making multiple changes
+it may be necessary to follow this call with a further call to
+.BR tcgetattr ()
+to check that all changes have been performed successfully.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbx lb lb
+l l l.
+Interface	Attribute	Value
+T{
+.na
+.nh
+.BR tcgetattr (),
+.BR tcsetattr (),
+.BR tcdrain (),
+.BR tcflush (),
+.BR tcflow (),
+.BR tcsendbreak (),
+.BR cfmakeraw (),
+.BR cfgetispeed (),
+.BR cfgetospeed (),
+.BR cfsetispeed (),
+.BR cfsetospeed (),
+.BR cfsetspeed ()
+T}	Thread safety	MT-Safe
+.TE
+.\" FIXME: The markings are different from that in the glibc manual.
+.\" markings in glibc manual are more detailed:
+.\"
+.\"     tcsendbreak: MT-Unsafe race:tcattr(filedes)/bsd
+.\"     tcflow: MT-Unsafe race:tcattr(filedes)/bsd
+.\"
+.\" glibc manual says /bsd indicate the preceding marker only applies
+.\" when the underlying kernel is a BSD kernel.
+.\" So, it is safety in Linux kernel.
+.SH STANDARDS
+.TP
+.BR tcgetattr ()
+.TQ
+.BR tcsetattr ()
+.TQ
+.BR tcsendbreak ()
+.TQ
+.BR tcdrain ()
+.TQ
+.BR tcflush ()
+.TQ
+.BR tcflow ()
+.TQ
+.BR cfgetispeed ()
+.TQ
+.BR cfgetospeed ()
+.TQ
+.BR cfsetispeed ()
+.TQ
+.BR cfsetospeed ()
+POSIX.1-2008.
+.TP
+.BR cfmakeraw ()
+.TQ
+.BR cfsetspeed ()
+BSD.
+.SH HISTORY
+.TP
+.BR tcgetattr ()
+.TQ
+.BR tcsetattr ()
+.TQ
+.BR tcsendbreak ()
+.TQ
+.BR tcdrain ()
+.TQ
+.BR tcflush ()
+.TQ
+.BR tcflow ()
+.TQ
+.BR cfgetispeed ()
+.TQ
+.BR cfgetospeed ()
+.TQ
+.BR cfsetispeed ()
+.TQ
+.BR cfsetospeed ()
+POSIX.1-2001.
+.TP
+.BR cfmakeraw ()
+.TQ
+.BR cfsetspeed ()
+BSD.
+.SH NOTES
+UNIX\ V7 and several later systems have a list of baud rates
+where after the values
+.B B0
+through
+.B B9600
+one finds the two constants
+.BR EXTA ,
+.B EXTB
+("External A" and "External B").
+Many systems extend the list with much higher baud rates.
+.P
+The effect of a nonzero \fIduration\fP with
+.BR tcsendbreak ()
+varies.
+SunOS specifies a break of
+.I "duration\ *\ N"
+seconds, where \fIN\fP is at least 0.25, and not more than 0.5.
+Linux, AIX, DU, Tru64 send a break of
+.I duration
+milliseconds.
+FreeBSD and NetBSD and HP-UX and MacOS ignore the value of
+.IR duration .
+Under Solaris and UnixWare,
+.BR tcsendbreak ()
+with nonzero
+.I duration
+behaves like
+.BR tcdrain ().
+.\" libc4 until 4.7.5, glibc for sysv: EINVAL for duration > 0.
+.\" libc4.7.6, libc5, glibc for unix: duration in ms.
+.\" glibc for bsd: duration in us
+.\" glibc for sunos4: ignore duration
+.SH BUGS
+.\" kernel 77e5bff1640432f28794a00800955e646dcd7455
+.\" glibc 573963e32ffac46d9891970ddebde2ac3212c5c0
+On the Alpha architecture before Linux 4.16 (and glibc before glibc 2.28), the
+.B XTABS
+value was different from
+.B TAB3
+and it was ignored by the
+.B N_TTY
+line discipline code of the terminal driver as a result
+(because as it wasn't part of the
+.B TABDLY
+mask).
+.SH SEE ALSO
+.BR reset (1),
+.BR setterm (1),
+.BR stty (1),
+.BR tput (1),
+.BR tset (1),
+.BR tty (1),
+.BR ioctl_console (2),
+.BR ioctl_tty (2),
+.BR cc_t (3type),
+.BR speed_t (3type),
+.BR tcflag_t (3type),
+.BR setserial (8)