Provided by: manpages-dev_3.35-0.1ubuntu1_all bug

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

SYNOPSIS

       #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(): _BSD_SOURCE

DESCRIPTION

       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  only  exposed  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  IGNPAR is not set, prefix a character with a parity error or framing error with
              \377 \0.  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 defined in POSIX.1:

       OPOST  Enable implementation-defined output processing.

       The remaining c_oflag flag constants are defined in POSIX.1-2001, unless marked otherwise.

       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 Don't output CR.

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

       OFDEL  (not in POSIX) 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).  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 on Linux.)

       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 IECHO 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
              function 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 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).

       In noncanonical mode input is available immediately (without the user  having  to  type  a
       line-delimiter character), and line editing is disabled.  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: 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: read(2) blocks until the lesser of MIN bytes or the number of bytes
         requested are available, and returns the lesser of these two values.

       * MIN == 0; TIME > 0: 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.

       * MIN  > 0; TIME > 0: 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 either when the lesser of the number of bytes requested or
         MIN byte have been read, or when the inter-byte timeout expires.  Because the  timer  is
         only started after the initial byte becomes available, at least one byte will be read.

   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 that 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

       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.

       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 zero, 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

       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.

CONFORMING TO

       tcgetattr(),  tcsetattr(),  tcsendbreak(),  tcdrain(), tcflush(), tcflow(), cfgetispeed(),
       cfgetospeed(), cfsetispeed(), and cfsetospeed() are specified in POSIX.1-2001.

       cfmakeraw() and cfsetspeed() are nonstandard, but available on the BSDs.

NOTES

       UNIX V7 and several later systems have a list of  baud  rates  where  after  the  fourteen
       values  B0,  ..., 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().

SEE ALSO

       stty(1), console_ioctl(4), tty_ioctl(4), setserial(8)

COLOPHON

       This page is part of release 3.35 of the Linux man-pages project.  A  description  of  the
       project,  and information about reporting bugs, can be found at http://man7.org/linux/man-
       pages/.