tty(P)                                                   tty(P)





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 internationaliza-
              tion 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  cate-
              gories.)

       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 mes-
              sages 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 stan-
       dard 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 Operat-
       ing  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.open-
       group.org/unix/online.html .



POSIX                         2003                       tty(P)
