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  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 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, 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(P)