TERMIOS(3)          Linux Programmer's Manual          TERMIOS(3)

NAME
       termios,   tcgetattr,   tcsetattr,  tcsendbreak,  tcdrain,
       tcflush,  tcflow,  cfmakeraw,  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 );

       int cfmakeraw ( struct termios *termios_p );

       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 */

       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  char-
              acter 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 charac-
              ters preceded by \.  On output,  uppercase  charac-
              ters are preceded by \ and lowercase characters 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  0x40
              greater  than  the  control  signal.   For example,
              character 0x08 (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
       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:

       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.

       cfmakeraw sets the terminal attributes 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;

       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
       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
       setserial(8)

Linux                   September 2, 1995                       1