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Re: <n> == <n->?
- X-seq: zsh-workers 10488
- From: Zefram <zefram@xxxxxxxx>
- To: "[Johan Sundstr_m]" <johsu650@xxxxxxxxxxxxxx>
- Subject: Re: <n> == <n->?
- Date: Tue, 4 Apr 2000 22:01:34 +0100 (BST)
- Cc: zsh-workers@xxxxxxxxxxxxxx
- In-reply-to: <Pine.GSO.4.02.10004041813220.28633-100000@xxxxxxxxxxxxxxxxxxx> from "[Johan Sundstr_m]" at "Apr 4, 2000 07:00:42 pm"
- Mailing-list: contact zsh-workers-help@xxxxxxxxxxxxxx; run by ezmlm
[Johan Sundstr_m] wrote:
>Sounds reasonable. After some digging through zshmisc(1), I'd guess the
>situation we're trying to protect from a possible ambiguity is "< word" --
>am I right?
> I may be at a loss here, but I don't quite see where the
>problem might arise. Could someone depict an example or two and how to
>trigger the problem?
zsh treats this as a command line with two words, one of which is a glob
pattern that will match "00234foo" and so on. Bourne shell syntax has
this meaning the same as the way both zsh and sh interpret
cat <123-456 >foo
which is a command line with one word and two redirections (input from
"123-456", output to "foo"). It's quite common to omit spaces before
and after redirection operators.
>I noticed them being different (which showed better using cat than echo),
>but I failed to understand how the first case tried to operate; to me, it
>seemed like a broken effort at <<- or <<<, but then I guess I just didn't
>understand what happened, so my guess isn't worth a lot. :-]
What actually happens if you type "echo a<1" (before my patch) is that
the lexer sees a word "echo", then sees another word that starts with
"a". After the "<", it looks for a ">" to finish that glob operator;
it gets a newline, which is treated as part of the word, then it asks
for more input, still reading that word. Try typing "x>y" as the second
input line to complete the word.
Completely broken behaviour, nothing to do with here documents.
>Either way, I'm not sure I see the impact of this on the case where the
>word continues with a > and possibly more pattern matching. After all,
>when I want redirection, I don't try my luck at inserting a < or > in
>the middle of the current word I'm typing,
Quite. The practical rarity of the syntax clash is the only reason that
we can get away with that as a glob syntax. The reason for requiring the
"-" is to make the clash as small and as simply bounded as possible.
> and I haven't found anything in
>the man pages supporting that behaviour either.
It's not clear on where whitespace is permitted. Whitespace is allowed
but not required before and after redirection operators.
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