NAME

       tcgetattr - get the parameters associated with the terminal

SYNOPSIS

       #include <termios.h>

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

DESCRIPTION

       The  tcgetattr() function shall get the parameters associated with the terminal referred to by fildes and
       store them in the termios structure referenced by  termios_p.   The  fildes  argument  is  an  open  file
       descriptor associated with a terminal.

       The termios_p argument is a pointer to a termios structure.

       The tcgetattr() operation is allowed from any process.

       If  the  terminal  device  supports  different  input and output baud rates, the baud rates stored in the
       termios structure returned by tcgetattr() shall reflect the actual baud rates, even if they are equal. If
       differing baud rates are not supported, the rate returned as the output baud rate  shall  be  the  actual
       baud  rate.  If  the terminal device does not support split baud rates, the input baud rate stored in the
       termios structure shall be the output rate (as one of the symbolic values).

RETURN VALUE

       Upon successful completion, 0 shall be returned. Otherwise,  -1  shall  be  returned  and  errno  set  to
       indicate the error.

ERRORS

       The tcgetattr() function shall fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       ENOTTY The file associated with fildes is not a terminal.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       Care  must  be  taken when changing the terminal attributes. Applications should always do a tcgetattr(),
       save the termios structure values returned, and then  do  a  tcsetattr(),  changing  only  the  necessary
       fields.  The  application  should  use  the values saved from the tcgetattr() to reset the terminal state
       whenever it is done with the terminal. This  is  necessary  because  terminal  attributes  apply  to  the
       underlying  port  and  not  to  each  individual open instance; that is, all processes that have used the
       terminal see the latest attribute changes.

       A program that uses these functions should be written to catch all signals  and  take  other  appropriate
       actions  to  ensure that when the program terminates, whether planned or not, the terminal device's state
       is restored to its original state.

       Existing practice dealing with error returns when only part of a request can be honored is based on calls
       to the ioctl() function. In historical BSD  and  System  V  implementations,  the  corresponding  ioctl()
       returns  zero  if  the requested actions were semantically correct, even if some of the requested changes
       could not be made. Many existing applications assume this behavior and would no longer work correctly  if
       the return value were changed from zero to -1 in this case.

       Note that either specification has a problem. When zero is returned, it implies everything succeeded even
       if  some of the changes were not made. When -1 is returned, it implies everything failed even though some
       of the changes were made.

       Applications that need all of the requested changes made to work properly should follow tcsetattr()  with
       a call to tcgetattr() and compare the appropriate field values.

FUTURE DIRECTIONS

       None.

SEE ALSO

       tcsetattr()  ,  the  Base  Definitions  volume  of  IEEE Std 1003.1-2001,  Chapter  11,  General Terminal
       Interface, <termios.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc  and  The  Open Group. In the event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                                   2003                                          TCGETATTR(P)