Section: POSIX Programmer's Manual (1P)
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.
--- return user's terminal name
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
function defined in the System Interfaces volume of POSIX.1-2017.
utility shall conform to the Base Definitions volume of POSIX.1-2017,
, Utility Syntax Guidelines.
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.
The following environment variables shall affect the execution of
Provide a default value for the internationalization variables that are
unset or null. (See the Base Definitions volume of POSIX.1-2017,
Section 8.2, Internationalization Variables
for the precedence of internationalization variables used to determine
the values of locale categories.)
If set to a non-empty string value, override the values of all the
other internationalization variables.
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).
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.
Determine the location of message catalogs for the processing of
If standard input is a terminal device, a pathname of the terminal as
specified by the
function defined in the System Interfaces volume of POSIX.1-2017 shall be written in the following
"%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
utility shall use the format:
"not a tty\n"
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
Standard input is a terminal.
Standard input is not a terminal.
An error occurred.
CONSEQUENCES OF ERRORS
The following sections are informative.
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).
The Base Definitions volume of POSIX.1-2017,
, Environment Variables,
, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1-2017,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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
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