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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 differ (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 ter-
       minal  that  is  open as standard input. The name that is used shall be
       equivalent to the string that would be returned by the ttyname()  func-
       tion 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  Vari-
              ables  for the precedence 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  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  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  for-
       mat:

              "%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(), tty-
       name()
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,  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 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 .

IEEE/The Open Group                  2003                              TTY(1P)