PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

       tcgetattr — get the parameters associated with the terminal

SYNOPSIS         top

       #include <termios.h>

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

DESCRIPTION         top

       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         top

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

ERRORS         top

       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         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       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         top

       None.

SEE ALSO         top

       tcsetattr(3p)

       The Base Definitions volume of POSIX.1‐2008, Chapter 11, General
       Terminal Interface, termios.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                       TCGETATTR(3P)