The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> ttyname, ttyname_r - find the pathname of a terminal

#### SYNOPSIS

> ``#include <unistd.h>
> char *ttyname(int` fildes`);
> int ttyname_r(int` fildes`, char *`name`, size_t` namesize`);
> ``

#### DESCRIPTION

> The ttyname() function shall return a pointer to a string containing a null-terminated pathname of the terminal associated with file descriptor fildes. The application shall not modify the string returned. The returned pointer might be invalidated or the string content might be overwritten by a subsequent call to ttyname(). The returned pointer and the string content might also be invalidated if the calling thread is terminated.

> The ttyname() function need not be thread-safe.

> The ttyname_r() function shall store the null-terminated pathname of the terminal associated with the file descriptor fildes in the character array referenced by name. The array is namesize characters long and should have space for the name and the terminating null character. The maximum length of the terminal name shall be {TTY_NAME_MAX}.

#### RETURN VALUE

> Upon successful completion, ttyname() shall return a pointer to a string. Otherwise, a null pointer shall be returned and errno set to indicate the error.

> If successful, the ttyname_r() function shall return zero. Otherwise, an error number shall be returned to indicate the error.

#### ERRORS

> The ttyname() function may fail if:

> [EBADF]
>   The fildes argument is not a valid file descriptor.
> [ENOTTY]
>   The file associated with the fildes argument is not a terminal.

> The ttyname_r() function may fail if:

> [EBADF]
>   The fildes argument is not a valid file descriptor.
> [ENOTTY]
>   The file associated with the fildes argument is not a terminal.
> [ERANGE]
>   The value of namesize is smaller than the length of the string to be returned including the terminating null character.

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> None.

#### RATIONALE

> The term ``terminal'' is used instead of the historical term ``terminal device'' in order to avoid a reference to an undefined term.

> The thread-safe version places the terminal name in a user-supplied buffer and returns a non-zero value if it fails. The non-thread-safe version may return the name in a static data area that may be overwritten by each call.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> XBD <unistd.h>

#### CHANGE HISTORY

> First released in Issue 1. Derived from Issue 1 of the SVID.

#### Issue 5

> The ttyname_r() function is included for alignment with the POSIX Threads Extension.

> A note indicating that the ttyname() function need not be reentrant is added to the DESCRIPTION.

#### Issue 6

> The ttyname_r() function is marked as part of the Thread-Safe Functions option.

> The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

> - The statement that errno is set on error is added.

> - The [EBADF] and [ENOTTY] optional error conditions are added.

#### Issue 7

> Austin Group Interpretation 1003.1-2001 #156 is applied.

> SD5-XSH-ERN-100 is applied, correcting the definition of the [ENOTTY] error condition.

> The ttyname_r() function is moved from the Thread-Safe Functions option to the Base.

> POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0686 [75] is applied.

> POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0376 [656] is applied.

End of informative text.

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