TTYNAME(3)                OpenBSD Programmer's Manual               TTYNAME(3)

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



SYNOPSIS
     #include <unistd.h>

     char *
     ttyname(int fd);

     int
     ttyname_r(int fd, char *name, size_t namesize);

     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 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() and ttyname_r() functions get the related device name of a
     file descriptor for which isatty() is true.  The ttyname_r() function
     stores the null-terminated pathname of the terminal associated with the
     file descriptor fd in the character array referenced by name. The array
     is namesize characters long and should have space for the name and the
     terminating NUL character. The maximum length of the terminal name is
     TTY_NAME_MAX.

     The ttyslot() function fetches the current process's control terminal
     number from the ttys(5) file entry.

RETURN VALUES
     The ttyname() and ttyname_r() functions return 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.

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.

     [ERANGE]      The value of namesize is smaller than the length of the
                   string to be returned including the terminating NUL charac-
                   ter.

FILES

     /dev/*
     /etc/ttys

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

HISTORY
     The isatty(), ttyname(), and ttyslot() functions appeared in Version 7
     AT&T UNIX.  The ttyname_r() function appeared in the POSIX Threads Exten-
     sion (1003.1c-1995).

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.

OpenBSD 2.6                      June 4, 1993                                2