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 internationalization 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 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 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 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 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 Operating 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.opengroup.org/unix/online.html .