Path: utzoo!attcan!uunet!lll-winken!ncis.llnl.gov!helios.ee.lbl.gov!nosc!ucsd!rutgers!gatech!cwjcc!hal!ncoast!allbery
From: allbery@ncoast.UUCP (Brandon S. Allbery)
Newsgroups: comp.sys.ibm.pc
Subject: Re: ...INT 21 ...
Message-ID: <13355@ncoast.UUCP>
Date: 21 Jan 89 19:46:07 GMT
References: <6798@killer.DALLAS.TX.US>
Reply-To: allbery@ncoast.UUCP (Brandon S. Allbery)
Followup-To: comp.sys.ibm.pc
Organization: Cleveland Public Access UN*X, Cleveland, Oh
Lines: 63

As quoted from <6798@killer.DALLAS.TX.US> by dono@killer.DALLAS.TX.US (Don OConnell):
+---------------
| >From allbery@ncoast.UUCP Sat Jan 14 23:28:32 1989
| >invoking it on the pathname \DEV\CON -- and, to my surprise, it returned
| >with an attribute byte of 40H!  In playing with it, I discovered that
| >\DEV\CON was the *only* device that produced this behavior; other devices,
| >and \DEV\*.*, returned AX=3 (path not found).
|                SHOULD BE 2-^
+---------------

(1) The actual return was AX=3.  Use of actual nonexistent paths returned
    AX=2, as expected.  And my DOS manual seemed to be saying that AX=3 means
    the same thing as AX=2.  Anyone know what it was *really* trying to tell
    me?

+---------------
| >Anyone know if I hit a fluke or if this actually happens?  Does it have to
| >do with the device being open by the program (i.e. \DEV\CON is
| >stdin/stdout/stderr -- but then, \DEV\CON1 should be open as stdaux and
| >\DEV\LPT1 as stdprn)?
| 
| Yes DOS does have some /dev files, though they are not the standard UNIX 
| names, ie.:
+---------------

I obviously should have been more clear; although the fact that I explicitly
mentioned some of the other pathnames *should* have given people a clue.
THIS WAS NOT THE QUESTION -- I'm quite aware of the "virtual" \DEV\*
pathnames.  My question was:  why does "find first" on \DEV\CON work, but
"find first" of \DEV\NUL, etc. fail?  After all, DOS recognizes them in e.g.
"open".  (Oh, \DEV\CON1 was a typo, I meant \DEV\COM1.)  [Sorry for the
tone, I seem to be getting lots of responses of this type.]

The surprise came from the fact that I thought "open" did something special
with \DEV\*, and that other DOS calls didn't recognize it; after all, my HD
doesn't *have* a \DEV directory.  And yet at least one device path was
recognized by "find first".  I would have expected either all of them or
none of them -- *not* just \DEV\CON and nothing else.

+---------------
| >From allbery@ncoast.UUCP Sat Jan 14 23:34:04 1989
| >The only copy of the Interrupt List I can find on ncoast and my almost
| >useless DOS manual agree that the structure set by INT 21, AH=4EH/4FH
| >contains one 16-bit entity each for file date and time.  Question:  does
| >anyone know the format of these numbers?
| 
| INT 21 - DOS 2+ - FIND FIRST ASCIZ (FIND FIRST)
> ...
|               bytes 18h-19h: file date
|               bytes 1Ah-1Dh: file size
+---------------

Please note I said "numbers", *not* "structures".  I was after the format of
the date and time, not of the "find first/next" buffer which I already have.
I've already received this information from others; thanks to all who
responded.

++Brandon
-- 
Brandon S. Allbery, moderator of comp.sources.misc    allbery@ncoast.org (soon)
uunet!hal.cwru.edu!ncoast!allbery		    ncoast!allbery@hal.cwru.edu
      Send comp.sources.misc submissions to comp-sources-misc@<backbone>
NCoast Public Access UN*X - (216) 781-6201, 300/1200/2400 baud, login: makeuser