isatty(3) - NetBSD Manual Pages

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TTYNAME(3)                NetBSD Programmer's 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 type-
     def, 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 and
     errno is set to indicate the error.

     The isatty() function returns 1 if fd is associated with a terminal de-
     vice; 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 IEEE Std 1003.1-1990
     (``POSIX'').


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 mod-
     ify the same object.

NetBSD 1.6.2                     June 4, 1993                                2