tty man page


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.

tty — return user's terminal name


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.1‐2008.


The tty utility shall conform to the Base Definitions volume of POSIX.1‐2008, Section 12.2, 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.

Environment Variables

The following environment variables shall affect the execution of tty:

Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.1‐2008, 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 LC_MESSAGES.

Asynchronous Events



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.1‐2008 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"


The standard error shall be used only for diagnostic messages.

Exit Status

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.

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).

See Also

The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines

The System Interfaces volume of POSIX.1‐2008, isatty(), ttyname()