ron@celerity.UUCP (Ron McDaniels) (05/15/84)
<>
Here's one that will test your wizard status. Take a look at inode.h in BSD 4.2,
in particular the lines following the comment, "/* modes */". Note that the mask
for the file-type field is 4 bits wide. Now look at the following lines which
#define the valid bit combinations for file-type. As you can see, there seems
to be a deliberate attempt not to use the least significant bit position in the
field. I have perused the source for "ls.c" in an attempt to find an not-so-
obvious use for this bit, alas, to no avail.
By way of explanation, three possible scenarios occur to me.
1. There is a hidden use for the bit (if not hidden, will you give me "not
obvious"?).
2. There used to be a use for the bit or there is currently a use for the bit
in Ma Bell's version of unix, and the bit is left unused in 4.2 to maintain
compatibility.
3. The primal inode definition defined the first few fields as even and all the
subsequent additions were made even for the same reason that I am asking the
question, ignorance and inadequate documentation.
Whatever the reason, I'd like to know what's going on. Opinions will be
appreciated. . . but not nearly as much as facts.
R. L. McDaniels
CELERITY COMPUTING
9692 Via Excelencia
San Diego, California 92126
(619) 566-0416
{decvax!ucbvax || ihnp4 || philabs}!sdcsvax!celerity!rongwyn@brl-vgr.UUCP (05/15/84)
Mode 010000 on AT&T UNIX is a FIFO special file (named pipe). It is nice that Berkeley avoided assigning this to something else since this improves compatibility between the two flavors of UNIX.