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TTY(1P)                    POSIX Programmer's Manual                   TTY(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

NAME
       tty - return user's terminal name

SYNOPSIS
       tty

DESCRIPTION
       The tty utility shall write to the standard output the name of the terminal that is open as standard input. The
       name that is used shall be equivalent to the string that would be returned by the ttyname() function defined in
       the System Interfaces volume of IEEE Std 1003.1-2001.

OPTIONS
       The  tty  utility  shall  conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility
       Syntax Guidelines.

OPERANDS
       None.

STDIN
       While no input is read from standard input, standard input shall be examined to determine whether or not it  is
       a terminal, and, if so, to determine the name of the terminal.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of tty:

       LANG   Provide  a  default  value  for the internationalization variables that are unset or null. (See the Base
              Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for  the  prece-
              dence of internationalization variables used to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.

       LC_CTYPE
              Determine the locale for the interpretation of sequences of bytes of text data as characters (for  exam-
              ple, single-byte as opposed to multi-byte characters in arguments).

       LC_MESSAGES
              Determine  the locale that should be used to affect the format and contents of diagnostic messages writ-
              ten to standard error and informative messages written to standard output.

       NLSPATH
              Determine the location of message catalogs for the processing of LC_MESSAGES .


ASYNCHRONOUS EVENTS
       Default.

STDOUT
       If standard input is a terminal device, a pathname of the terminal  as  specified  by  the  ttyname()  function
       defined in the System Interfaces volume of IEEE Std 1003.1-2001 shall be written in the following format:


              "%s\n", <terminal name>

       Otherwise,  a  message  shall  be written indicating that standard input is not connected to a terminal. In the
       POSIX locale, the tty utility shall use the format:


              "not a tty\n"

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0     Standard input is a terminal.

        1     Standard input is not a terminal.

       >1     An error occurred.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       This utility checks the status of the file open as standard input against that of an implementation-defined set
       of  files. It is possible that no match can be found, or that the match found need not be the same file as that
       which was opened for standard input (although they are the same device).

EXAMPLES
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       The System Interfaces volume of IEEE Std 1003.1-2001, isatty(), ttyname()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, 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                              TTY(1P)