termios(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | HISTORY | NOTES | BUGS | SEE ALSO

termios(3)              Library Functions Manual              termios(3)

NAME         top

       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

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <termios.h>
       #include <unistd.h>

       int tcgetattr(int fd, struct termios *termios_p);
       int tcsetattr(int fd, int optional_actions,
                     const struct termios *termios_p);

       int tcsendbreak(int fd, int duration);
       int tcdrain(int fd);
       int tcflush(int fd, int queue_selector);
       int tcflow(int fd, int action);

       void cfmakeraw(struct termios *termios_p);

       speed_t cfgetispeed(const struct termios *termios_p);
       speed_t cfgetospeed(const struct termios *termios_p);

       int cfsetispeed(struct termios *termios_p, speed_t speed);
       int cfsetospeed(struct termios *termios_p, speed_t speed);
       int cfsetspeed(struct termios *termios_p, speed_t speed);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       cfsetspeed(), cfmakeraw():
           Since glibc 2.19:
               _DEFAULT_SOURCE
           glibc 2.19 and earlier:
               _BSD_SOURCE

DESCRIPTION         top

       The termios functions describe a general terminal interface that
       is provided to control asynchronous communications ports.

   The termios structure
       Many of the functions described here have a termios_p argument
       that is a pointer to a termios structure.  This structure
       contains at least the following members:

           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 */

       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
       feature_test_macros(7)) is defined, as noted in brackets ("[]").

       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.

       c_iflag flag constants:

       IGNBRK Ignore BREAK condition on input.

       BRKINT If IGNBRK is set, a BREAK is ignored.  If it is not set
              but BRKINT 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 SIGINT to be sent to this foreground process
              group.  When neither IGNBRK nor BRKINT are set, a BREAK
              reads as a null byte ('\0'), except when PARMRK is set, in
              which case it reads as the sequence \377 \0 \0.

       IGNPAR Ignore framing errors and parity errors.

       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 INPCK is set and IGNPAR is not set.
              The way erroneous bytes are marked is with two preceding
              bytes, \377 and \0.  Thus, the program actually reads
              three bytes for one erroneous byte received from the
              terminal.  If a valid byte has the value \377, and ISTRIP
              (see below) is not set, the program might confuse it with
              the prefix that marks a parity error.  Therefore, a valid
              byte \377 is passed to the program as two bytes, \377
              \377, in this case.

              If neither IGNPAR nor PARMRK is set, read a character with
              a parity error or framing error as \0.

       INPCK  Enable input parity checking.

       ISTRIP Strip off eighth bit.

       INLCR  Translate NL to CR on input.

       IGNCR  Ignore carriage return on input.

       ICRNL  Translate carriage return to newline on input (unless
              IGNCR is set).

       IUCLC  (not in POSIX) Map uppercase characters to lowercase on
              input.

       IXON   Enable XON/XOFF flow control on output.

       IXANY  (XSI) Typing any character will restart stopped output.
              (The default is to allow just the START character to
              restart output.)

       IXOFF  Enable XON/XOFF flow control on input.

       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.

       IUTF8 (since Linux 2.6.4)
              (not in POSIX) Input is UTF8; this allows character-erase
              to be correctly performed in cooked mode.

       c_oflag flag constants:

       OPOST  Enable implementation-defined output processing.

       OLCUC  (not in POSIX) Map lowercase characters to uppercase on
              output.

       ONLCR  (XSI) Map NL to CR-NL on output.

       OCRNL  Map CR to NL on output.

       ONOCR  Don't output CR at column 0.

       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.

       OFILL  Send fill characters for a delay, rather than using a
              timed delay.

       OFDEL  Fill character is ASCII DEL (0177).  If unset, fill
              character is ASCII NUL ('\0').  (Not implemented on
              Linux.)

       NLDLY  Newline delay mask.  Values are NL0 and NL1.  [requires
              _BSD_SOURCE or _SVID_SOURCE or _XOPEN_SOURCE]

       CRDLY  Carriage return delay mask.  Values are CR0, CR1, CR2, or
              CR3.  [requires _BSD_SOURCE or _SVID_SOURCE or
              _XOPEN_SOURCE]

       TABDLY Horizontal tab delay mask.  Values are TAB0, TAB1, TAB2,
              TAB3 (or XTABS, but see the BUGS section).  A value of
              TAB3, that is, XTABS, expands tabs to spaces (with tab
              stops every eight columns).  [requires _BSD_SOURCE or
              _SVID_SOURCE or _XOPEN_SOURCE]

       BSDLY  Backspace delay mask.  Values are BS0 or BS1.  (Has never
              been implemented.)  [requires _BSD_SOURCE or _SVID_SOURCE
              or _XOPEN_SOURCE]

       VTDLY  Vertical tab delay mask.  Values are VT0 or VT1.

       FFDLY  Form feed delay mask.  Values are FF0 or FF1.  [requires
              _BSD_SOURCE or _SVID_SOURCE or _XOPEN_SOURCE]

       c_cflag flag constants:

       CBAUD  (not in POSIX) Baud speed mask (4+1 bits).  [requires
              _BSD_SOURCE or _SVID_SOURCE]

       CBAUDEX
              (not in POSIX) Extra baud speed mask (1 bit), included in
              CBAUD.  [requires _BSD_SOURCE or _SVID_SOURCE]

              (POSIX says that the baud speed is stored in the termios
              structure without specifying where precisely, and provides
              cfgetispeed() and cfsetispeed() for getting at it.  Some
              systems use bits selected by CBAUD in c_cflag, other
              systems use separate fields, for example, sg_ispeed and
              sg_ospeed.)

       CSIZE  Character size mask.  Values are CS5, CS6, CS7, or CS8.

       CSTOPB Set two stop bits, rather than one.

       CREAD  Enable receiver.

       PARENB Enable parity generation on output and parity checking for
              input.

       PARODD If set, then parity for input and output is odd; otherwise
              even parity is used.

       HUPCL  Lower modem control lines after last process closes the
              device (hang up).

       CLOCAL Ignore modem control lines.

       LOBLK  (not in POSIX) Block output from a noncurrent shell layer.
              For use by shl (shell layers).  (Not implemented on
              Linux.)

       CIBAUD (not in POSIX) Mask for input speeds.  The values for the
              CIBAUD bits are the same as the values for the CBAUD bits,
              shifted left IBSHIFT bits.  [requires _BSD_SOURCE or
              _SVID_SOURCE] (Not implemented in glibc, supported on
              Linux via TCGET* and TCSET* ioctls; see ioctl_tty(2))

       CMSPAR (not in POSIX) Use "stick" (mark/space) parity (supported
              on certain serial devices): if PARODD is set, the parity
              bit is always 1; if PARODD is not set, then the parity bit
              is always 0.  [requires _BSD_SOURCE or _SVID_SOURCE]

       CRTSCTS
              (not in POSIX) Enable RTS/CTS (hardware) flow control.
              [requires _BSD_SOURCE or _SVID_SOURCE]

       c_lflag flag constants:

       ISIG   When any of the characters INTR, QUIT, SUSP, or DSUSP are
              received, generate the corresponding signal.

       ICANON Enable canonical mode (described below).

       XCASE  (not in POSIX; not supported under Linux) If ICANON is
              also set, terminal is uppercase only.  Input is converted
              to lowercase, except for characters preceded by \.  On
              output, uppercase characters are preceded by \ and
              lowercase characters are converted to uppercase.
              [requires _BSD_SOURCE or _SVID_SOURCE or _XOPEN_SOURCE]

       ECHO   Echo input characters.

       ECHOE  If ICANON is also set, the ERASE character erases the
              preceding input character, and WERASE erases the preceding
              word.

       ECHOK  If ICANON is also set, the KILL character erases the
              current line.

       ECHONL If ICANON is also set, echo the NL character even if ECHO
              is not set.

       ECHOCTL
              (not in POSIX) If ECHO is also set, terminal special
              characters other than TAB, NL, START, and STOP are echoed
              as ^X, where X is the character with ASCII code 0x40
              greater than the special character.  For example,
              character 0x08 (BS) is echoed as ^H.  [requires
              _BSD_SOURCE or _SVID_SOURCE]

       ECHOPRT
              (not in POSIX) If ICANON and ECHO are also set, characters
              are printed as they are being erased.  [requires
              _BSD_SOURCE or _SVID_SOURCE]

       ECHOKE (not in POSIX) If ICANON is also set, KILL is echoed by
              erasing each character on the line, as specified by ECHOE
              and ECHOPRT.  [requires _BSD_SOURCE or _SVID_SOURCE]

       DEFECHO
              (not in POSIX) Echo only when a process is reading.  (Not
              implemented on Linux.)

       FLUSHO (not in POSIX; not supported under Linux) Output is being
              flushed.  This flag is toggled by typing the DISCARD
              character.  [requires _BSD_SOURCE or _SVID_SOURCE]

       NOFLSH Disable flushing the input and output queues when
              generating signals for the INT, QUIT, and SUSP characters.

       TOSTOP Send the SIGTTOU signal to the process group of a
              background process which tries to write to its controlling
              terminal.

       PENDIN (not in POSIX; not supported under Linux) All characters
              in the input queue are reprinted when the next character
              is read.  (bash(1) handles typeahead this way.)  [requires
              _BSD_SOURCE or _SVID_SOURCE]

       IEXTEN Enable implementation-defined input processing.  This
              flag, as well as ICANON must be enabled for the special
              characters EOL2, LNEXT, REPRINT, WERASE to be interpreted,
              and for the IUCLC flag to be effective.

       The c_cc array defines the terminal special characters.  The
       symbolic indices (initial values) and meaning are:

       VDISCARD
              (not in POSIX; not supported under Linux; 017, SI, Ctrl-O)
              Toggle: start/stop discarding pending output.  Recognized
              when IEXTEN is set, and then not passed as input.

       VDSUSP (not in POSIX; not supported under Linux; 031, EM, Ctrl-Y)
              Delayed suspend character (DSUSP): send SIGTSTP signal
              when the character is read by the user program.
              Recognized when IEXTEN and ISIG are set, and the system
              supports job control, and then not passed as input.

       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 read(2) in the user program returns 0, which signifies
              end-of-file.  Recognized when ICANON is set, and then not
              passed as input.

       VEOL   (0, NUL) Additional end-of-line character (EOL).
              Recognized when ICANON is set.

       VEOL2  (not in POSIX; 0, NUL) Yet another end-of-line character
              (EOL2).  Recognized when ICANON is set.

       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 ICANON is set, and
              then not passed as input.

       VINTR  (003, ETX, Ctrl-C, or also 0177, DEL, rubout) Interrupt
              character (INTR).  Send a SIGINT signal.  Recognized when
              ISIG is set, and then not passed as input.

       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 ICANON is set, and
              then not passed as input.

       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 IEXTEN is set,
              and then not passed as input.

       VMIN   Minimum number of characters for noncanonical read (MIN).

       VQUIT  (034, FS, Ctrl-\) Quit character (QUIT).  Send SIGQUIT
              signal.  Recognized when ISIG is set, and then not passed
              as input.

       VREPRINT
              (not in POSIX; 022, DC2, Ctrl-R) Reprint unread characters
              (REPRINT).  Recognized when ICANON and IEXTEN are set, and
              then not passed as input.

       VSTART (021, DC1, Ctrl-Q) Start character (START).  Restarts
              output stopped by the Stop character.  Recognized when
              IXON is set, and then not passed as input.

       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 SIGINFO signal (not supported on Linux) to
              the foreground process group.

       VSTOP  (023, DC3, Ctrl-S) Stop character (STOP).  Stop output
              until Start character typed.  Recognized when IXON is set,
              and then not passed as input.

       VSUSP  (032, SUB, Ctrl-Z) Suspend character (SUSP).  Send SIGTSTP
              signal.  Recognized when ISIG is set, and then not passed
              as input.

       VSWTCH (not in POSIX; not supported under Linux; 0, NUL) Switch
              character (SWTCH).  Used in System V to switch shells in
              shell layers, a predecessor to shell job control.

       VTIME  Timeout in deciseconds for noncanonical read (TIME).

       VWERASE
              (not in POSIX; 027, ETB, Ctrl-W) Word erase (WERASE).
              Recognized when ICANON and IEXTEN are set, and then not
              passed as input.

       An individual terminal special character can be disabled by
       setting the value of the corresponding c_cc element to
       _POSIX_VDISABLE.

       The above symbolic subscript values are all different, except
       that VTIME, VMIN may have the same value as VEOL, VEOF,
       respectively.  In noncanonical mode the special character meaning
       is replaced by the timeout meaning.  For an explanation of VMIN
       and VTIME, see the description of noncanonical mode below.

   Retrieving and changing terminal settings
       tcgetattr() gets the parameters associated with the object
       referred by fd and stores them in the termios structure
       referenced by termios_p.  This function may be invoked from a
       background process; however, the terminal attributes may be
       subsequently changed by a foreground process.

       tcsetattr() sets the parameters associated with the terminal
       (unless support is required from the underlying hardware that is
       not available) from the termios structure referred to by
       termios_p.  optional_actions specifies when the changes take
       effect:

       TCSANOW
              the change occurs immediately.

       TCSADRAIN
              the change occurs after all output written to fd has been
              transmitted.  This option should be used when changing
              parameters that affect output.

       TCSAFLUSH
              the change occurs after all output written to the object
              referred by fd has been transmitted, and all input that
              has been received but not read will be discarded before
              the change is made.

   Canonical and noncanonical mode
       The setting of the ICANON canon flag in c_lflag determines
       whether the terminal is operating in canonical mode (ICANON set)
       or noncanonical mode (ICANON unset).  By default, ICANON is set.

       In canonical mode:

       •  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
          read(2).

       •  Line editing is enabled (ERASE, KILL; and if the IEXTEN flag
          is set: WERASE, REPRINT, LNEXT).  A read(2) returns at most
          one line of input; if the 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 read(2).

       •  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.,
          ISIG and 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.

       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 (c_cc[VMIN]) and TIME
       (c_cc[VTIME]) determine the circumstances in which a read(2)
       completes; there are four distinct cases:

       MIN == 0, TIME == 0 (polling read)
              If data is available, read(2) returns immediately, with
              the lesser of the number of bytes available, or the number
              of bytes requested.  If no data is available, read(2)
              returns 0.

       MIN > 0, TIME == 0 (blocking read)
              read(2) blocks until MIN bytes are available, and returns
              up to the number of bytes requested.

       MIN == 0, TIME > 0 (read with timeout)
              TIME specifies the limit for a timer in tenths of a
              second.  The timer is started when read(2) is called.
              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, read(2)
              returns 0.  If data is already available at the time of
              the call to read(2), the call behaves as though the data
              was received immediately after the call.

       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.  read(2) returns when any of the following
              conditions is met:

              •  MIN bytes have been received.

              •  The interbyte timer expires.

              •  The number of bytes requested by read(2) has been
                 received.  (POSIX does not specify this termination
                 condition, and on some other implementations read(2)
                 does not return in this case.)

              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
              read(2), the call behaves as though the data was received
              immediately after the call.

       POSIX does not specify whether the setting of the O_NONBLOCK file
       status flag takes precedence over the MIN and TIME settings.  If
       O_NONBLOCK is set, a 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 read(2) in
       noncanonical mode to return either 0, or -1 with errno set to
       EAGAIN.

   Raw mode
       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:

           termios_p->c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP
                           | INLCR | IGNCR | ICRNL | IXON);
           termios_p->c_oflag &= ~OPOST;
           termios_p->c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
           termios_p->c_cflag &= ~(CSIZE | PARENB);
           termios_p->c_cflag |= CS8;

   Line control
       tcsendbreak() transmits a continuous stream of zero-valued bits
       for a specific duration, if the terminal is using asynchronous
       serial data transmission.  If duration is zero, it transmits
       zero-valued bits for at least 0.25 seconds, and not more than 0.5
       seconds.  If duration is not zero, it sends zero-valued bits for
       some implementation-defined length of time.

       If the terminal is not using asynchronous serial data
       transmission, tcsendbreak() returns without taking any action.

       tcdrain() waits until all output written to the object referred
       to by fd has been transmitted.

       tcflush() discards data written to the object referred to by fd
       but not transmitted, or data received but not read, depending on
       the value of queue_selector:

       TCIFLUSH
              flushes data received but not read.

       TCOFLUSH
              flushes data written but not transmitted.

       TCIOFLUSH
              flushes both data received but not read, and data written
              but not transmitted.

       tcflow() suspends transmission or reception of data on the object
       referred to by fd, depending on the value of action:

       TCOOFF suspends output.

       TCOON  restarts suspended output.

       TCIOFF transmits a STOP character, which stops the terminal
              device from transmitting data to the system.

       TCION  transmits a START character, which starts the terminal
              device transmitting data to the system.

       The default on open of a terminal file is that neither its input
       nor its output is suspended.

   Line speed
       The baud rate functions are provided for getting and setting the
       values of the input and output baud rates in the termios
       structure.  The new values do not take effect until tcsetattr()
       is successfully called.

       Setting the speed to B0 instructs the modem to "hang up".  The
       actual bit rate corresponding to B38400 may be altered with
       setserial(8).

       The input and output baud rates are stored in the termios
       structure.

       cfgetospeed() returns the output baud rate stored in the termios
       structure pointed to by termios_p.

       cfsetospeed() sets the output baud rate stored in the termios
       structure pointed to by termios_p to speed, which must be one of
       these constants:

              B0
              B50
              B75
              B110
              B134
              B150
              B200
              B300
              B600
              B1200
              B1800
              B2400
              B4800
              B9600
              B19200
              B38400
              B57600
              B115200
              B230400
              B460800
              B500000
              B576000
              B921600
              B1000000
              B1152000
              B1500000
              B2000000

       These constants are additionally supported on the SPARC
       architecture:

              B76800
              B153600
              B307200
              B614400

       These constants are additionally supported on non-SPARC
       architectures:

              B2500000
              B3000000
              B3500000
              B4000000

       Due to differences between architectures, portable applications
       should check if a particular Bnnn constant is defined prior to
       using it.

       The zero baud rate, B0, is used to terminate the connection.  If
       B0 is specified, the modem control lines shall no longer be
       asserted.  Normally, this will disconnect the line.  CBAUDEX is a
       mask for the speeds beyond those defined in POSIX.1 (57600 and
       above).  Thus, B57600 & CBAUDEX is nonzero.

       Setting the baud rate to a value other than those defined by Bnnn
       constants is possible via the TCSETS2 ioctl; see ioctl_tty(2).

       cfgetispeed() returns the input baud rate stored in the termios
       structure.

       cfsetispeed() sets the input baud rate stored in the termios
       structure to speed, which must be specified as one of the Bnnn
       constants listed above for cfsetospeed().  If the input baud rate
       is set to the literal constant 0 (not the symbolic constant B0),
       the input baud rate will be equal to the output baud rate.

       cfsetspeed() is a 4.4BSD extension.  It takes the same arguments
       as cfsetispeed(), and sets both input and output speed.

RETURN VALUE         top

       cfgetispeed() returns the input baud rate stored in the termios
       structure.

       cfgetospeed() returns the output baud rate stored in the termios
       structure.

       All other functions return:

       0      on success.

       -1     on failure and set errno to indicate the error.

       Note that tcsetattr() returns success if any 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 tcgetattr() to check that all changes have
       been performed successfully.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌─────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                           Attribute     Value   │
       ├─────────────────────────────────────┼───────────────┼─────────┤
       │ tcgetattr(), tcsetattr(),           │ Thread safety │ MT-Safe │
       │ tcdrain(), tcflush(), tcflow(),     │               │         │
       │ tcsendbreak(), cfmakeraw(),         │               │         │
       │ cfgetispeed(), cfgetospeed(),       │               │         │
       │ cfsetispeed(), cfsetospeed(),       │               │         │
       │ cfsetspeed()                        │               │         │
       └─────────────────────────────────────┴───────────────┴─────────┘

STANDARDS         top

       tcgetattr()
       tcsetattr()
       tcsendbreak()
       tcdrain()
       tcflush()
       tcflow()
       cfgetispeed()
       cfgetospeed()
       cfsetispeed()
       cfsetospeed()
              POSIX.1-2008.

       cfmakeraw()
       cfsetspeed()
              BSD.

HISTORY         top

       tcgetattr()
       tcsetattr()
       tcsendbreak()
       tcdrain()
       tcflush()
       tcflow()
       cfgetispeed()
       cfgetospeed()
       cfsetispeed()
       cfsetospeed()
              POSIX.1-2001.

       cfmakeraw()
       cfsetspeed()
              BSD.

NOTES         top

       UNIX V7 and several later systems have a list of baud rates where
       after the values B0 through B9600 one finds the two constants
       EXTA, EXTB ("External A" and "External B").  Many systems extend
       the list with much higher baud rates.

       The effect of a nonzero duration with tcsendbreak() varies.
       SunOS specifies a break of duration * N seconds, where N is at
       least 0.25, and not more than 0.5.  Linux, AIX, DU, Tru64 send a
       break of duration milliseconds.  FreeBSD and NetBSD and HP-UX and
       MacOS ignore the value of duration.  Under Solaris and UnixWare,
       tcsendbreak() with nonzero duration behaves like tcdrain().

BUGS         top

       On the Alpha architecture before Linux 4.16 (and glibc before
       glibc 2.28), the XTABS value was different from TAB3 and it was
       ignored by the N_TTY line discipline code of the terminal driver
       as a result (because as it wasn't part of the TABDLY mask).

SEE ALSO         top

       reset(1), setterm(1), stty(1), tput(1), tset(1), tty(1),
       ioctl_console(2), ioctl_tty(2), cc_t(3type), speed_t(3type),
       tcflag_t(3type), setserial(8)

Linux man-pages (unreleased)     (date)                       termios(3)

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