@node _chmod, file system
@subheading Syntax
 
@example
#include <io.h>
 
int _chmod(const char *filename, int func, mode_t mode);
@end example
 
@subheading Description
 
This is a direct connection to the MS-DOS chmod function call, int
0x21, %ax = 0x4300/0x4301.  If @var{func} is 0, then DOS is called with
AX = 0x4300, which returns an attribute byte of a file.  If @var{func}
is 1, then the attributes of a file are set as specified in @var{mode}.
Note that the directory and volume attribute bits must always be 0 when
@code{_chmod()} is called with @var{func = 1}, or else the call will fail.
The third argument is optional when getting attributes.
The attribute bits are defined as follows:
 
@example
  Bit       Meaning
76543210
.......1    Read-only
......1.    Hidden
.....1..    System
....1...    Volume Label
...1....    Directory
..1.....    Archive
xx......    Reserved (used by some network redirectors)
@end example

On platforms where the LFN API (@pxref{_use_lfn, LFN}) is available,
@code{_chmod} calls function 0x7143 of Interrupt 21h, to support long
file names.
 
@subheading Return Value
 
If the file exists, @code{_chmod()} returns its attribute byte in case
it succeded, or -1 in case of failure.


@subheading Portability

@portability !ansi, !posix