[Coco] Megaread problems

[Dave Philipsen]

That's good to know.  With that in mind I suppose one could even modify 
megaread to automatically include the '@' if it found that the path 
provided in the command line pointed to a device.

On 3/27/2017 2:49 PM, Bill Pierce via Coco wrote:
> 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.

Of course a directory is a file.  Just a special kind of file...:-)

> 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).

It would probably be handy for 'copy' to be able to do that.  Since 
'ded' correctly computes the size of the device, we know it can be 
done.  That way you could use the 'copy' command to backup an entire 
device if you wanted.

>   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.
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> 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
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