Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!snorkelwacker!ai-lab!friedman@apple-gunkies.ai.mit.edu
From: friedman@apple-gunkies.ai.mit.edu (Noah Friedman)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Long command lines
Summary: There should be no command-line length limit at all
Message-ID: <10379@life.ai.mit.edu>
Date: 31 Aug 90 17:46:38 GMT
References: <2954@mindlink.UUCP> <2677@dataio.Data-IO.COM>
Sender: news@ai.mit.edu
Organization: The Free Software Foundation
Lines: 38

In article <2677@dataio.Data-IO.COM> bright@Data-IO.COM (Walter Bright) writes:
>In article <2954@mindlink.UUCP> a269@mindlink.UUCP (Mischa Sandberg) writes:
><4DOS does exactly that. 4DOS is a replacement for COMMAND.COM
><that seriously improves on MS's command shell. It can only put
><the firs 127 bytes into the PSP, but up to 256 bytes goes into
><the environment, coincidentally into a variable named "CMDLINE".
><Why they limit it to 256 bytes I haven't the foggiest.
>
>Limiting it to 256 bytes only defers the problem for a little while...
>A better limit would be 64k.

Among other problems, when the command string is stored in the PSP,
the first byte is used to store the length. I guess this value must be
treated as signed, because 8 bits allows for a maximum (unsigned)
value of 255.

I started to write an MS-DOS compatible system, but I found that there
were so many bugs and stupid designs that I couldn't in good
conscience reproduce them. I hope to design a filesystem that allows
filenames of arbitrary length and characters (except for '/' and ASCII
0) and command-line length of a similar nature. I think I can even
improve on DOS's process management. 

Of course, this doesn't help the average DOS user, since my os
wouldn't be able to run DOS programs. 

I don't know of any way to get a commercial program to read a command
line greater than 128 characters, because they get this list from the
PSP. In your own programs, you might try using the two FCB blocks in
the PSP if they aren't being used for some other purpose (I don't
think DOS uses them anymore) to store arguments and retrieve them. Of
course, this also involves writing your own command shell to PUT those
arguments there, since command.com won't.

---
Noah Friedman
friedman@ai.mit.edu
my new OS, I'm