Mail Archives: djgpp/2002/12/13/16:06:30
> From: "Arthur J. O'Dwyer" <ajo AT andrew DOT cmu DOT edu>
> Newsgroups: comp.os.msdos.djgpp
> Date: Fri, 13 Dec 2002 12:26:14 -0500 (EST)
>
> So when I use quotes, I am usually in my mental "Unix mode", and I
> expect the quotes to behave as closely to Unix as possible.
They do behave close to Unix, but not as close as you expected. I
explained the reasons for the differences: they are required to let
DOS/Windows users be comfortable with the command-line handling and in
particular with native DOSish file names. What you suggest--making \
escape any character including itself--would require doubling every
backslash in a file name, which is IMHO a ridiculous requirement for
DOS/Windows users.
> Wht do you mean, "Some cases of mismatched quotes are actually the
> shell's fault"? How much globbing (by which I mean generic "argument
> parsing") is done by the shell (by which I mean COMMAND.COM)? My
> experience from assembler programming is that COMMAND.COM doesn't
> do any parsing of arguments at all; it's entirely up to the client.
Please look in versions of COMMAND.COM from latest Windows releases,
and you will see that they do know about quotes (they need that for
file names with embedded whitespace and other special characters). On
some Windows 9X systems, long command lines with unmatched quotes can
actually crash the DOS box (due to a bug in COMMAND.COM)--a clear sign
that the shell does process the quotes.
> A. Sinan Unur points out that
>
> % test.exe "*"\ hello
>
> works
Yes, this is the recommended solution to such situations.
> but it looks like an incredibly flimsy hack to me
I fail to see why is this a ``flimsy hack''. The same will work on
Unix, for example.
> and I wouldn't be surprised if it stopped working in future versions
> of DJGPP
I would be surprised if this will ever change. There's too much
working code and scripts out there that depend on this.
>(because the next guy who looks at the globbing code might not
> know this hack is out there).
Please look in the library sources and point out where do you see the
terrible hack which someone would like to take out. I think you will
find that there's no such hack, i.e. there's no special code that
allows "*"\ and its ilk to do what you want. Rather, it's a simple
consequence of the design, namely, that a backslash escapes only the
quotes and nothing else, and is not stripped away unless the following
character is not a quote.
In other words, if some J. Random Hacker would like in the future to
remove this ``hack'', he or she will have to redesign the whole thing
and then rewrite it from scratch.
> In bash or ksh (as the nice folks in comp.unix.misc have informed
> me), the following command line does what I want:
>
> tr -d '.?\\' *.txt
>
> With DJGPP in MS-DOS, the best I can do is
>
> tr -d ".?"\ *.txt
>
> and I've already explained that this just looks bad.
You have chosen a design of a program based on Unixy shell behavior.
That's why it works on Unix, but only half-works in DJGPP. Should
you, e.g., choose " as your escape character, you'd have problems on
Unix as well.
So I dare to claim that you dislike the DJGPP behavior because you've
chosen an unportable design that won't work with any globbing but the
strictly Posix one.
Personally, I don't see why ".?"\ ``looks bad'', but if you don't like
it, the best solution for your problem is to write your own globbing
function. The rest of this thread has enough pointers to
documentation to let you do that.
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