NAME
	  ttyname, ttyname_r, isatty - Gets the	name of	a terminal

     LIBRARY
	  Standard C Library (libc.a)

     SYNOPSIS
	  #include <unistd.h>
	  char *ttyname(
	       int file_descriptor );
	  int isatty(
	       int file_descriptor );
	  int ttyname_r(
	       int file_descriptor,
	       char *buffer,
	       int len );


     PARAMETERS
	  file_descriptor
		    Specifies an open file descriptor.

	  buffer    Points to a	buffer in which	the terminal name is
		    stored.

	  len	    Specifies the length of the	buffer pointed to by
		    the	buffer parameter.


     DESCRIPTION
	  The ttyname()	function gets the name of a terminal.  It
	  returns a pointer to a string	containing the null-terminated
	  pathname of the terminal device associated with the
	  file_descriptor parameter.

	  The isatty() function	determines if the device associated
	  with the file_descriptor parameter is	a terminal.  If	so,
	  the isatty() function	returns	a value	of 1.  If the file
	  descriptor is	not associated with a terminal,	a value	of 0
	  (zero) is returned.

	  The ttyname_r() function is the reentrant version of the
	  ttyname() function.  Upon successful completion, the termi-
	  nal name is stored as	a null-terminated string in the	buffer
	  pointed to by	the buffer parameter.

     NOTES
	  AES Support Level:
			 Full use


     RETURN VALUES

	  The ttyname()	function returns a pointer to a	string which
	  is static data that is overwritten by	each call.  A null
	  pointer is returned if the file_descriptor parameter does
	  not describe a terminal device in the	directory /dev.

	  The isatty() function	returns	a value	of 1 if	the specified
	  file descriptor is associated	with a terminal, and 0 (zero)
	  otherwise.

	  The ttyname_r() function returns 0 (zero) if successful.
	  Otherwise, -1	is returned.

     ERRORS
	  If the ttyname_r() function fails, errno may be set to the
	  following value:


	  [EINVAL]  The	buffer parameter is a null pointer or the len
		    parameter was too short to store the string.

	  [ENOENT]  The	file_descriptior could not be found.


	  If the isatty() function fails, errno	may be set to the fol-
	  lowing value:


	  [ENOTTY]  The	file associated	with filedes is	not a termi-
		    nal.


     RELATED INFORMATION
	  Functions: ttyslot(3)