[Coco] Megaread problems

[Bill Pierce]

Dave, Tim, Robert etc, You can't "megaread" "/dd". As Dave stated it's a directory and not a file, so error 214 was correct.
The help message is not "wrong", just incomplete. The "@" is a standard in OS9 directive for opening and reading the "raw" device (it's in the manual) and anyone having read the manual, should know this :-P.
Many programs can use "@" as a directive and very few of those state so in their helpfiles.
In that respect, "Copy" would not work as copy assumes a definate file size (obtained from the file descriptor) and "@" has no file size, therefore would run forever (bad error trapping?) or error out. For copy to work with "@" it would have to read LSN0 to get the drive size (not part of the copy code).
 Megaread on the otherhand, works with "@" because you state a file size (or default size) and it will come to a stop at the said file size.

 

 


Bill Pierce
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-----Original Message-----
From: Dave Philipsen <dave at davebiz.com>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Mon, Mar 27, 2017 2:25 pm
Subject: Re: [Coco] Megaread problems

So, I *think* that the real problem is that /dd is a directory.  And in order to read a directory it has to be opened in a different way than a regular file. I haven't written any file manipulation code for OS9 in years so I'd have to look this up in the tech manual but I'm guessing that when you open a file for reading you may have to specify that it's a directory if it actually is one.  As an example, the disk editor 'ded' will correctly open a root directory and read it in (ded /dd).  Additionally, megaread will correctly read from a regular file but if the regular file is shorter than what megaread wants to read then it will just finish early without errors.  So 'megaread /dd/bigfile' works but only provides useful information if 'bigfile' is at least one megabyte in size.DaveOn 3/27/2017 1:02 PM, Robert Gault wrote:> Tim Fadden wrote:>> <snip>>> So it is something system wide?  and not megaread itself?>>>>>> Any how just wanted to let you know your not loosing it. :-)>>>> In a way :). The help message is incorrect for this utility and should > indicate that a raw read is necessary, ex. megaread </DD@>> Robert>>-- Coco mailing listCoco at maltedmedia.comhttps://pairlist5.pair.net/mailman/listinfo/coco