@node _get_dev_info, io
@subheading Syntax

@example
#include <io.h>

short _get_dev_info(int handle);
@end example

@subheading Description

Given a file handle in @var{handle}, this function returns the info word
from DOS IOCTL function 0 (Int 21h/AX=4400h).  @var{handle} must refer
to an open file or device, otherwise the call will fail (and set
@var{errno} to @code{EBADF}).

In case of success, the returned value is the coded information from the
system about the character device or the file which is referenced by the
file handle @var{handle}.  The following table shows the meaning of the
individual bits in the return value:

For a character device:

@multitable {Bit(s)} {Device can process IOCTL functions 02h and 03h}
@item Bit(s) @tab Description
@item 14 @tab Device can process IOCTL functions 02h and 03h
@item 13 @tab Device supports output-until-busy
@item 11 @tab Device supports OPEN/CLOSE calls
@item 8  @tab Unknown; set by MS-DOS 6.2x @file{KEYB@var{xx}.COM}
@item 7  @tab Always set for character devices
@item 6  @tab End of file on input
@item 5  @tab Device is in @strong{raw} (binary) mode
@item 4  @tab Device uses Int 29h
@item 3  @tab Clock device
@item 2  @tab NUL device
@item 1  @tab Standard output device
@item 0  @tab Standard input device
@end multitable

For a block device (a disk file):

@multitable {Bit(s)} {Generate Int 24h if full disk or read past EOF}
@item Bit(s) @tab Description
@item 15 @tab Device is remote (networked drive)
@item 14 @tab Don't set file time stamp on close
@item 11 @tab If set, non-removable media
@item 11 @tab If clear, media is removable (e.g. floppy disk)
@item 8  @tab Generate Int 24h if full disk or read past EOF
@item 7  @tab Always clear for disk files
@item 6  @tab File has not been written to
@item 5-0 @tab Drive number (0 = A:)
@end multitable

Note that the functionality indicated by bit 8 for the block devices is
only supported by DOS version 4.

@dfn{Cooked} mode means that on input @kbd{C-@key{C}}, @kbd{C-@key{P}},
@kbd{C-@key{S}} and @kbd{C-@key{Z}} are processed, on output @samp{TAB}s
are expanded into spaces and @samp{CR} character is added before each
@samp{LF}, and input is terminated when the @key{RET} key is pressed.
In contrast, in @dfn{raw} mode, all the special characters are passed
verbatim, and the read operation waits until the specified number of
characters has been read.

@subheading Return Value

The device information word described above.  In case of error, -1 is
returned and @var{errno} is set to @code{EBADF}.

@subheading Portability

@portability !ansi, !posix

@subheading Example

@example
 int fd = open ("CLOCK$", O_RDONLY | O_BINARY);
 int clock_info = _get_dev_info (fd);
@end example