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tcgetattr(3p) — Linux manual page

TCGETATTR(3P)           POSIX Programmer's ManualTCGETATTR(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(intfildes, struct termios *termios_p);

DESCRIPTION        top

       Thetcgetattr() function shall get the parameters associated with       the terminal referred to byfildes and store them in thetermios       structure referenced bytermios_p.  Thefildes argument is an open       file descriptor associated with a terminal.       Thetermios_p argument is a pointer to atermiosstructure.       Thetcgetattr() operation is allowed from any process.       If the terminal device supports different input and output baud       rates, the baud rates stored in thetermiosstructure returned bytcgetattr() 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 thetermiosstructure 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 anderrno set to indicate the error.

ERRORS        top

       Thetcgetattr() function shall fail if:EBADFThefildes argument is not a valid file descriptor.ENOTTYThe file associated withfildes 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 atcgetattr(), save thetermios       structure values returned, and then do atcsetattr(), changing       only the necessary fields. The application should use the values       saved from thetcgetattr() 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 theioctl() function.       In historical BSD and System V implementations, the correspondingioctl() 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 followtcsetattr() with a call totcgetattr() and       compare the appropriate field values.

FUTURE DIRECTIONS        top

       None.

SEE ALSO        top

tcsetattr(3p)       The Base Definitions volume of POSIX.1‐2017,Chapter 11,GeneralTerminal Interface,termios.h(0p)

COPYRIGHT        top

       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 athttp://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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group                2017TCGETATTR(3P)

Pages that refer to this page:termios.h(0p), cfgetispeed(3p), cfgetospeed(3p), tcsetattr(3p)

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