1TTY(1P)                    POSIX Programmer's Manual                   TTY(1P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       tty — return user's terminal name
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SYNOPSIS

15       tty
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DESCRIPTION

18       The tty utility shall write to the standard output the name of the ter‐
19       minal  that  is  open as standard input. The name that is used shall be
20       equivalent to the string that would be returned by the ttyname()  func‐
21       tion defined in the System Interfaces volume of POSIX.1‐2017.
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OPTIONS

24       The  tty  utility  shall  conform  to  the  Base  Definitions volume of
25       POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
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OPERANDS

28       None.
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STDIN

31       While no input is read from standard input,  standard  input  shall  be
32       examined  to  determine whether or not it is a terminal, and, if so, to
33       determine the name of the terminal.
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INPUT FILES

36       None.
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ENVIRONMENT VARIABLES

39       The following environment variables shall affect the execution of tty:
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41       LANG      Provide a default value for  the  internationalization  vari‐
42                 ables  that are unset or null. (See the Base Definitions vol‐
43                 ume of POSIX.1‐2017, Section 8.2, Internationalization  Vari‐
44                 ables  for  the  precedence of internationalization variables
45                 used to determine the values of locale categories.)
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47       LC_ALL    If set to a non-empty string value, override  the  values  of
48                 all the other internationalization variables.
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50       LC_CTYPE  Determine  the  locale for the interpretation of sequences of
51                 bytes of text data as characters (for example, single-byte as
52                 opposed to multi-byte characters in arguments).
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54       LC_MESSAGES
55                 Determine the locale that should be used to affect the format
56                 and contents of diagnostic messages written to standard error
57                 and informative messages written to standard output.
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59       NLSPATH   Determine the location of message catalogs for the processing
60                 of LC_MESSAGES.
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ASYNCHRONOUS EVENTS

63       Default.
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STDOUT

66       If standard input is a terminal device, a pathname of the  terminal  as
67       specified  by  the  ttyname() function defined in the System Interfaces
68       volume of POSIX.1‐2017 shall be written in the following format:
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71           "%s\n", <terminal name>
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73       Otherwise, a message shall be written indicating that standard input is
74       not connected to a terminal. In the POSIX locale, the tty utility shall
75       use the format:
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78           "not a tty\n"
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STDERR

81       The standard error shall be used only for diagnostic messages.
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OUTPUT FILES

84       None.
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EXTENDED DESCRIPTION

87       None.
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EXIT STATUS

90       The following exit values shall be returned:
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92        0    Standard input is a terminal.
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94        1    Standard input is not a terminal.
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96       >1    An error occurred.
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CONSEQUENCES OF ERRORS

99       Default.
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101       The following sections are informative.
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APPLICATION USAGE

104       This utility checks the status of  the  file  open  as  standard  input
105       against  that of an implementation-defined set of files. It is possible
106       that no match can be found, or that the match found  need  not  be  the
107       same  file  as  that which was opened for standard input (although they
108       are the same device).
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EXAMPLES

111       None.
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RATIONALE

114       None.
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FUTURE DIRECTIONS

117       None.
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SEE ALSO

120       The Base Definitions volume of  POSIX.1‐2017,  Chapter  8,  Environment
121       Variables, Section 12.2, Utility Syntax Guidelines
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123       The System Interfaces volume of POSIX.1‐2017, isatty(), ttyname()
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126       Portions  of  this text are reprinted and reproduced in electronic form
127       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
128       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
129       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
130       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
131       event of any discrepancy between this version and the original IEEE and
132       The  Open Group Standard, the original IEEE and The Open Group Standard
133       is the referee document. The original Standard can be  obtained  online
134       at http://www.opengroup.org/unix/online.html .
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136       Any  typographical  or  formatting  errors that appear in this page are
137       most likely to have been introduced during the conversion of the source
138       files  to  man page format. To report such errors, see https://www.ker‐
139       nel.org/doc/man-pages/reporting_bugs.html .
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143IEEE/The Open Group                  2017                              TTY(1P)
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