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    Command:

    tcgetattr

    
           speed - 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.
                  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.
    
           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 struc-
                  ture  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  sepa-
                  rate 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.
    
                  (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 char-
                  acters 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 imple-
                  mented 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]
    
                  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) Tog-
                  gle: start/stop discarding pending output.  Recognized when IEX-
                  TEN 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 charac-
                  ter (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 charac-
                  ter (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.
    
                  (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 sig-
                  nal.  Recognized when ISIG is set, and then not passed as input.
    
           VSWTCH (not in POSIX; not supported under Linux; 0, NUL) Switch charac-
                  ter (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).  Recog-
                  nized 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 pro-
           cess.
    
           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 trans-
                  mitted.  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
    
           * 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), no input processing is per-
           formed, 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  immedi-
             ately,  with the lesser of the number of bytes available, or the num-
             ber 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 interbyte timeout expires.  Because the
             timer is started only 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  charac-
           ter,  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
    
           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 struc-
           ture 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
    
           beyond those defined in POSIX.1 (57600  and  above).   Thus,  B57600  &
           CBAUDEX is nonzero.
    
           cfgetispeed()  returns the input baud rate stored in the termios struc-
           ture.
    
           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  struc-
           ture.
    
           cfgetospeed() returns the output baud rate stored in the termios struc-
           ture.
    
           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

       Multithreading (see pthreads(7))
           The  tcgetattr(),  tcsetattr(),  tcsendbreak(),  tcdrain(),  tcflush(),
           tcflow(),  cfmakeraw(),  cfgetispeed(),  cfgetospeed(),  cfsetispeed(),
           cfsetospeed(), and cfsetspeed() functions are thread-safe.
    
    
    

    CONFORMING TO

           tcgetattr(),   tcsetattr(),   tcsendbreak(),   tcdrain(),    tcflush(),
           tcflow(),   cfgetispeed(),   cfgetospeed(),  cfsetispeed(),  and  cfse-
           tospeed() 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.
    
    
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