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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)
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