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TCGETATTR(3P)              POSIX Programmer's Manual             TCGETATTR(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
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  descrip-
       tor 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 differ-
       ing 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 tcge-
       tattr() to reset the terminal state whenever it is done with the termi-
       nal.  This is necessary because terminal attributes apply to the under-
       lying port and not to each individual open instance; that is, all  pro-
       cesses that have used the terminal see the latest attribute changes.
       A program that uses these functions should be written to catch all sig-
       nals 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 prop-
       erly 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, Chap-
       ter 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(3P)