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 POSIX.1-2024.

OPTIONS

The tty utility shall conform to XBD 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 XBD 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

^[XSI] Determine the location of messages objects and message catalogs.

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 POSIX.1-2024 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, and the output specified in STDOUT was successfully written to standard output.

 1

Standard input is not a terminal, and the output specified in STDOUT was successfully written to standard output.

>1

An error occurred.

CONSEQUENCES OF ERRORS

Default.

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

XBD 8. Environment Variables , 12.2 Utility Syntax Guidelines

XSH isatty , ttyname

CHANGE HISTORY

First released in Issue 2.

Issue 5

The SYNOPSIS is changed to indicate two forms of the command, with the second form marked as obsolete. This is a clarification and does not change the functionality published in previous issues.

Issue 6

The obsolescent -s option is removed.

Issue 8

Austin Group Defect 1122 is applied, changing the description of NLSPATH .

Austin Group Defect 1509 is applied, changing the EXIT STATUS section.