ttyname, ttyname_r, isatty, ttyslot - get name of associated
(tty) from file descriptor
ttyname_r(int fd, char *name, size_t namesize);
These functions operate on the system file descriptors for
devices. These descriptors are not related to the standard
typedef, but refer to the special device files found in /dev
/dev/ttyXX and for which an entry exists in the initialization file
/etc/ttys (see ttys(5)).
The isatty() function determines if the file descriptor fd
refers to a
valid terminal type device.
The ttyname() and ttyname_r() functions get the related device name of a
file descriptor for which isatty() is true. The ttyname_r()
stores the null-terminated pathname of the terminal associated with the
file descriptor fd in the character array referenced by
name. The array
is namesize characters long and should have space for the
name and the
terminating NUL character. The maximum length of the terminal name is
The ttyslot() function fetches the current process's control
number from the ttys(5) file entry.
The ttyname() and ttyname_r() functions return the null-terminated name
if the device is found and isatty() is true; otherwise a
null pointer is
returned and errno is set to indicate the error.
The isatty() function returns 1 if fd is associated with a
otherwise it returns 0 and errno is set to indicate
The ttyslot() function returns the unit number of the device
found; otherwise the value zero is returned.
The ttyname() and isatty() functions will fail if:
[EBADF] The fd argument is not a valid file descriptor.
[ENOTTY] The fd argument does not refer to a terminal
[ERANGE] The value of namesize is smaller than the
length of the
string to be returned including the terminating NUL character.
ioctl(2), ttys(5), dev_mkdb(8)
The isatty(), ttyname(), and ttyslot() functions appeared in
AT&T UNIX. The ttyname_r() function appeared in the POSIX
The ttyname() function leaves its result in an internal
static object and
returns a pointer to that object. Subsequent calls to
modify the same object.
OpenBSD 3.6 June 4, 1993
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