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 differ (con-
       sult 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  Inter-
       faces 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 Guide-
       lines.

OPERANDS
       None.

STDIN
       While no input is read from standard input, standard input shall be examined to determine whether or not it is  a  termi-
       nal, 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 precedence  of  international-
              ization 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 example, 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 written to stan-
              dard 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, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                       TTY(1P)