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 .