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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 POSIX.1-2008.
OPTIONS
       The  tty  utility  shall  conform  to  the  Base  Definitions volume of
       POSIX.1-2008, 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  vari-
                 ables  that are unset or null. (See the Base Definitions vol-
                 ume of POSIX.1-2008, 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 POSIX.1-2008 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 Base Definitions volume of  POSIX.1-2008,  Chapter  8,  Environment
       Variables, Section 12.2, Utility Syntax Guidelines
       The System Interfaces volume of POSIX.1-2008, isatty(), ttyname()
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/online.html .
       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,  see  https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                              TTY(1P)