Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     char *
     ttyname(int fd);

     int
     isatty(int fd);

     int
     ttyslot(void);

DESCRIPTION

     These functions operate on the system file descriptors for terminal type
     devices.  These descriptors are not related to the standard I/O FILE
     typedef, but refer to the special device files found in /dev and named
     /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() function gets the related device name of a file descriptor
     for which isatty() is true

     The ttyslot() function fetches the current process' control terminal num-
     ber from the ttys(5) file entry.

RETURN VALUES

     The ttyname() function returns the null terminated name if the device is
     found and isatty() is true; otherwise a NULL pointer is returned.

     The ttyslot() function returns the unit number of the device file if
     found; otherwise the value zero is returned.

FILES

     /dev/*
     /etc/ttys

SEE ALSO

     ioctl(2), ttys(5)

HISTORY

     A isatty(), ttyname(), and ttyslot() function appeared in Version 7 AT&T
     UNIX.

BUGS

     The ttyname() function leaves its result in an internal static object and
     returns a pointer to that object.  Subsequent calls to ttyname() will
     modify the same object.