ttyname(3) Linux Man Page - System Grab Bag

Name

ttyname, ttyname_r - return name of a terminal

Library

Standard C library ( libc ", " -lc )

Synopsis

#include <unistd.h> 
char *ttyname(int  fd );
int ttyname_r(int " fd ", char " buf [. buflen "], size_t  buflen );

Description

The function ttyname() returns a pointer to the null-terminated pathname of the terminal device that is open on the file descriptor fd, or NULL on error (for example, if fd is not connected to a terminal). The return value may point to static data, possibly overwritten by the next call. The function ttyname_r() stores this pathname in the buffer buf of length buflen.

Return Value

The function ttyname() returns a pointer to a pathname on success. On error, NULL is returned, and errno is set to indicate the error. The function ttyname_r() returns 0 on success, and an error number upon error.

Errors

EBADF Bad file descriptor.

ENODEV fd refers to a slave pseudoterminal device but the corresponding pathname could not be found (see NOTES).

ENOTTY fd does not refer to a terminal device.

ERANGE ( ttyname_r ()) buflen was too small to allow storing the pathname.

Attributes

For an explanation of the terms used in this section, see attributes(7). allbox; lbx lb lb T{ ttyname()T{ ttyname_r()

Interface	Attribute	Value
T}	Thread safety	MT-Unsafe race:ttyname
T}	Thread safety	MT-Safe

Standards

POSIX.1-2008.

History

POSIX.1-2001, 4.2BSD.

Notes

A process that keeps a file descriptor that refers to a pts(4) device open when switching to another mount namespace that uses a different /dev/ptmx instance may still accidentally find that a device path of the same name for that file descriptor exists. However, this device path refers to a different device and thus can't be used to access the device that the file descriptor refers to. Calling ttyname() or ttyname_r() on the file descriptor in the new mount namespace will cause these functions to return NULL and set errno to ENODEV .