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tty(1)								       tty(1)



NAME

  tty -	Returns	pathname of terminal device

SYNOPSIS

  tty [-s]

  The tty command writes the full pathname of your terminal device to stan-
  dard output.	The tty	command	may also be used to determine if standard
  input	is a terminal.

STANDARDS

  Interfaces documented	on this	reference page conform to industry standards
  as follows:

  tty:	XCU5.0

  Refer	to the standards(5) reference page for more information	about indus-
  try standards	and associated tags.

OPTIONS

  -s  Suppresses reporting the pathname.

  The XCU specification	states that -s option is obsolete and recommends the
  portable applications	use test -t 0 instead of tty -s.

OPERANDS

  None

DESCRIPTION

  The command tty -s evaluates as TRUE if standard input is a display and
  FALSE	if it is not.

  [Tru64 UNIX]	The file /dev/tty is a special file always refers to your
  controlling terminal,	although it also may have another name like
  /dev/console or /dev/tty2.  To avoid writing undesirable output to an	out-
  put file--for	example, to write a prompt in a	shell script to	the screen,
  while	writing	the response to	the prompt to an output	file--redirect stan-
  dard output to /dev/tty.

NOTES

  While	the -s option is useful	if only	the exit code is wanted, it does not
  rely on any ability to form a	valid pathname.	For a portable application
  you should use the command test -t 0.




EXIT STATUS

  The following	exit values are	returned:

  0   Successful completion.

  1   Standard input is	not a display.

  2   [Tru64 UNIX]  Invalid options specified.

  >>2  [Tru64 UNIX]  An error occurred.

DIAGNOSTICS

  Standard input is not	a tty
      [Tru64 UNIX]  Your standard input	is not a display and you did not
      specify the -s option.

EXAMPLES

   1.  To display full pathname	of your	terminal device, enter:
	    tty

   2.  To test whether or not the standard input is a terminal device, create
       a shell script containing the following:
	    if tty -s
	    then
		    echo 'Output is a display'
	    else
		    echo 'Output is not	a display'
	    fi

       If the standard input is	a terminal device, this	displays the Output
       is a display message. If	the standard input is not a terminal device,
       it displays the Output is not a display message.

ENVIRONMENT VARIABLES

  The following	environment variables affect the execution of tty:

  LANG
      Provides a default value for the internationalization variables that
      are unset	or null. If LANG is unset or null, the corresponding value
      from the default locale is used.	If any of the internationalization
      variables	contain	an invalid setting, the	utility	behaves	as if none of
      the variables had	been defined.

  LC_ALL
      If set to	a non-empty string value, overrides the	values of all the
      other internationalization variables.

  LC_CTYPE
      Determines 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
      Determines the locale for	the format and contents	of diagnostic mes-
      sages written to standard	error.

  NLSPATH
      Determines the location of message catalogues for	the processing of
      LC_MESSAGES.



FILES

  /dev/tty
      Pseudodevice representing	the user's controlling terminal.


SEE ALSO

  Commands:  stty(1), test(1)

  Routines:  ttyname(3)

  Files:  tty(7)

  Standards:  standards(5)