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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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TCGETATTR(3P) POSIX Programmer's Manual TCGETATTR(3P)
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.
tcgetattr — get the parameters associated with the terminal
#include <termios.h>
int tcgetattr(int fildes, struct termios *termios_p);
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).
Upon successful completion, 0 shall be returned. Otherwise, -1
shall be returned and errno set to indicate the error.
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.
None.
None.
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.
None.
tcsetattr(3p)
The Base Definitions volume of POSIX.1‐2017, Chapter 11, General
Terminal Interface, termios.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
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 2017 TCGETATTR(3P)
Pages that refer to this page: termios.h(0p), cfgetispeed(3p), cfgetospeed(3p), tcsetattr(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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