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TTYNAME(3)                 Library Functions Manual                 TTYNAME(3)

     ttyname, ttyname_r, isatty, ttyslot - get name of associated terminal
     (tty) from file descriptor

     Standard C Library (libc, -lc)

     #include <unistd.h>

     char *
     ttyname(int fd);

     ttyname_r(int fd, char *buf, size_t len);

     isatty(int fd);

     #include <stdlib.h>


     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)), or for pseudo-terminal devices created in ptyfs
     and named /dev/pts/n.

     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 ttyname_r() is the reentrant version of
     the above, and it places the results in buf.  If there is not enough
     space to place the results (indicated by len), then it returns an error.

     The ttyslot() function fetches the current process' control terminal
     number from the ttys(5) file entry.  If the terminal is a pseudo-
     terminal, and there is no special entry in the ttys(5) file for it, the
     slot number returned is 1 + (last slot number) + minor(tty).  This will
     return a consistent and unique number for each pseudo-terminal device
     without requiring one to enumerate all of them in ttys(5).

     As an optimisation, these functions attempt to obtain information about
     all devices from the /var/run/dev.cdb database, if it exists.  If the
     database exists but is out of date, then these functions may produce
     incorrect results.  The database should be updated using the dev_mkdb(8)

     The ttyname() function returns the NUL-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 ttyname_r() functions returns 0 on success and an error code on

     The isatty() function returns 1 if fd is associated with a terminal
     device; otherwise it returns 0 and errno is set to indicate the error.

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


     The ttyname(), ttyname_r(), 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 device.

     The ttyname_r() function will also fail if:

     [ENOENT]           The terminal device is not found.  This can happen if
                        the device node has been removed after it was opened.

     [ERANGE]           The buffer provided is not large enough to fit the

     ioctl(2), ttys(5), dev_mkdb(8)

     The ttyname() and isatty() functions conform to IEEE Std 1003.1-1990

     isatty(), ttyname(), and ttyslot() functions appeared in Version 7 AT&T

     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.

NetBSD 10.99                     June 1, 2012                     NetBSD 10.99