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    TERMIOS(2)          Linux Programmer's Manual          TERMIOS(2)

    NAME
           termios,   tcgetattr,   tcsetattr,  tcsendbreak,  tcdrain,
           tcflush, tcflow,  cfgetospeed,  cfgetispeed,  cfsetispeed,
           cfsetospeed,  tcgetpgrp,  tcsetpgrp - get and set terminal
           attributes, line control, get and set baud rate,  get  and
           set terminal foreground process group ID

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

           int tcgetattr ( int fd, struct termios *termios_p );

           int tcsetattr ( int fd, int optional_actions, 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 );

           speed_t cfgetospeed ( struct termios *termios_p );

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

           speed_t cfgetispeed ( struct termios *termios_p );

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

           pid_t tcgetpgrp ( int fd );

           int tcsetpgrp ( int fd, pid_t pgrpid );

    DESCRIPTION
           The termios functions describe a general  terminal  inter-
           face  that  is provided to control asynchronous communica-
           tions ports.

           Many of the functions  described  here  have  a  termios_p
           argument  that  is a pointer to a termios structure.  This
           structure contains 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];       /* control chars */

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    TERMIOS(2)          Linux Programmer's Manual          TERMIOS(2)

           c_iflag flag constants:

           IGNBRK ignore BREAK condition on input

           BRKINT If IGNBRK is not set, generate SIGINT on BREAK con-
                  dition, else read BREAK as character \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  map uppercase characters to lowercase on input

           IXON   enable XON/XOFF flow control on output

           IXANY  enable any character to restart output

           IXOFF  enable XON/XOFF flow control on input

           IMAXBEL
                  ring bell when input queue is full

           c_oflag flag constants:

           OPOST  enable implementation-defined output processing

           OLCUC  map lowercase characters to uppercase on output

           ONLCR  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  fill  character  is  ASCII  DEL.   If  unset,  fill

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    TERMIOS(2)          Linux Programmer's Manual          TERMIOS(2)

                  character is ASCII NUL

           NLDLY  newline delay mask.  Values are NL0 and NL1.

           CRDLY  carriage  return  delay mask.  Values are CR0, CR1,
                  CR2, or CR3.

           TABDLY horizontal tab delay mask.  Values are TAB0,  TAB1,
                  TAB2,  TAB3,  or  XTABS.   A value of XTABS expands
                  tabs  to  spaces  (with  tab  stops   every   eight
                  columns).

           BSDLY  backspace delay mask.  Values are BS0 or BS1.

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

           FFDLY  form feed delay mask.  Values are FF0 or FF1.

           c_cflag flag constants:

           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 parity for input and output is odd.

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

           CLOCAL ignore modem control lines

           CIBAUD mask for input speeds (not used).

           CRTSCTS
                  flow control.

           c_lflag flag constants:

           ISIG   when any of the characters  INTR,  QUIT,  SUSP,  or
                  DSUSP are received, generate the corresponding sig-
                  nal.

           ICANON enable canonical mode.  This  enables  the  special
                  characters  EOF,  EOL,  EOL2, ERASE, KILL, REPRINT,
                  STATUS, and WERASE, and buffers by lines.

           XCASE  if ICANON is also set, terminal is uppercase  only.
                  Input   is   converted  to  lowercase,  except  for

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    TERMIOS(2)          Linux Programmer's Manual          TERMIOS(2)

                  characters preceded by  \.   On  output,  uppercase
                  characters  are preceded by \ and lowercase charac-
                  ters are converted to uppercase.

           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
                  if ECHO is also set, ASCII  control  signals  other
                  than  TAB,  NL,  START,  and STOP are echoed as ^X,
                  where X is  the  character  with  ASCII  code  0x10
                  greater  than  the  control  signal.   For example,
                  character 0x28 (BS) is echoed as ^H.

           ECHOPRT
                  if ICANON and IECHO are also  set,  characters  are
                  printed as they are being erased.

           ECHOKE if  ICANON  is  also set, KILL is echoed by erasing
                  each character on the line, as specified  by  ECHOE
                  and ECHOPRT.

           FLUSHO output  is  being flushed.  This flag is toggled by
                  typing the DISCARD character.

           NOFLSH disable flushing the input and output  queues  when
                  generating  the  SIGINT  and  SIGQUIT  signals, and
                  flushing the input queue when generating  the  SIG-
                  SUSP signal.

           TOSTOP send  the  SIGTTOU signal to the process group of a
                  background process which tries to write to its con-
                  trolling terminal.

           PENDIN all  characters  in  the  input queue are reprinted
                  when the next character  is  read.   (bash  handles
                  typeahead this way.)

           IEXTEN enable implementation-defined input processing.

           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

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    TERMIOS(2)          Linux Programmer's Manual          TERMIOS(2)

           process.

           tcsetattr() sets the parameters associated with the termi-
           nal  (unless support is required from the underlying hard-
           ware 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.

           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 sec-
           onds,  and  not more that 0.5 seconds.  If duration is not
           zero, it sends zero-valued bits  for  duration*N  seconds,
           where N is at least 0.25, and not more than 0.5.

           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:

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    TERMIOS(2)          Linux Programmer's Manual          TERMIOS(2)

           TCOOFF suspends output.

           TCOON  restarts suspended output.

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

           TCION  transmits a START character, which starts the  ter-
                  minal device transmitting data to the system.

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

           The baud rate functions are provided for getting and  set-
           ting  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 connec-
           tion.  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

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    TERMIOS(2)          Linux Programmer's Manual          TERMIOS(2)

           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.  If the input baud rate is set
           to  zero,  the input baud rate will be equal to the output
           baud rate.

           tcgetpgrp() returns process group ID  of  foreground  pro-
           cessing group, or -1 on error.

           tcsetpgrp()  sets process group ID to pgrpid.  pgrpid must
           be the ID of a process group in the same session.

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

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

           tcgetpgrp() returns process group ID  of  foreground  pro-
           cessing group, or -1 on error.

           All other functions return:

           0      on success.

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

### SEE ALSO

###

    Linux                   February 25, 1995                       7

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