'\" et

.TH TTY "1P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH 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.

.SH NAME

tty

\(em return user's terminal name

.SH SYNOPSIS

.LP

.nf

tty

.fi

.SH DESCRIPTION

The

.IR 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

\fIttyname\fR()

function defined in the System Interfaces volume of POSIX.1\(hy2008.

.SH OPTIONS

The

.IR tty

utility shall conform to the Base Definitions volume of POSIX.1\(hy2008,

.IR "Section 12.2" ", " "Utility Syntax Guidelines".

.SH OPERANDS

None.

.SH 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.

.SH "INPUT FILES"

None.

.SH "ENVIRONMENT VARIABLES"

The following environment variables shall affect the execution of

.IR tty :

.IP "\fILANG\fP" 10

Provide a default value for the internationalization variables that are

unset or null. (See the Base Definitions volume of POSIX.1\(hy2008,

.IR "Section 8.2" ", " "Internationalization Variables"

for the precedence of internationalization variables used to determine

the values of locale categories.)

.IP "\fILC_ALL\fP" 10

If set to a non-empty string value, override the values of all the

other internationalization variables.

.IP "\fILC_CTYPE\fP" 10

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).

.IP "\fILC_MESSAGES\fP" 10

.br

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.

.IP "\fINLSPATH\fP" 10

Determine the location of message catalogs for the processing of

.IR LC_MESSAGES .

.SH "ASYNCHRONOUS EVENTS"

Default.

.SH STDOUT

If standard input is a terminal device, a pathname of the terminal as

specified by the

\fIttyname\fR()

function defined in the System Interfaces volume of POSIX.1\(hy2008 shall be written in the following

format:

.sp

.RS 4

.nf

\fB

"%s\en", <\fIterminal name\fR>

.fi \fR

.P

.RE

.P

Otherwise, a message shall be written indicating that standard input is

not connected to a terminal. In the POSIX locale, the

.IR tty

utility shall use the format:

.sp

.RS 4

.nf

\fB

"not a tty\en"

.fi \fR

.P

.RE

.SH STDERR

The standard error shall be used only for diagnostic messages.

.SH "OUTPUT FILES"

None.

.SH "EXTENDED DESCRIPTION"

None.

.SH "EXIT STATUS"

The following exit values shall be returned:

.IP "\00" 6

Standard input is a terminal.

.IP "\01" 6

Standard input is not a terminal.

.IP >1 6

An error occurred.

.SH "CONSEQUENCES OF ERRORS"

Default.

.LP

.IR "The following sections are informative."

.SH "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).

.SH EXAMPLES

None.

.SH RATIONALE

None.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

The Base Definitions volume of POSIX.1\(hy2008,

.IR "Chapter 8" ", " "Environment Variables",

.IR "Section 12.2" ", " "Utility Syntax Guidelines"

.P

The System Interfaces volume of POSIX.1\(hy2008,

.IR "\fIisatty\fR\^(\|)",

.IR "\fIttyname\fR\^(\|)"

.SH 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

Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .