isatty(3) - NetBSD Manual Pages

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TTYNAME(3)              NetBSD Library Functions Manual             TTYNAME(3)


NAME

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


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <unistd.h>

     char *
     ttyname(int fd);

     int
     isatty(int fd);

     #include <stdlib.h>

     int
     ttyslot();


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)), 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 ttyslot() function fetches the current process' control terminal num-
     ber 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 con-
     sistent and unique number for each pseudo-terminal device without requir-
     ing one to enumerate all of them in ttys(5).


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 and
     errno is set to indicate the error.

     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.


FILES

     /dev/*
     /etc/ttys


ERRORS

     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 device.


SEE ALSO

     ioctl(2), ttys(5)


STANDARDS

     The ttyname() and isatty() functions conform to ISO/IEC 9945-1:1990
     (``POSIX.1'').


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.

NetBSD 3.0.1                   November 11, 2004                  NetBSD 3.0.1