From: Peter Stephenson <p.w.stephenson@ntlworld.com>
To: zsh-users@zsh.org
Subject: Re: {fd}< and compound commands
Date: Wed, 14 Sep 2011 20:06:01 +0100 [thread overview]
Message-ID: <20110914200601.72c91f87@pws-pc.ntlworld.com> (raw)
In-Reply-To: <20110914172148.GA7325@yahoo.fr>
On Wed, 14 Sep 2011 18:21:48 +0100
Stephane Chazelas <stephane_chazelas@yahoo.fr> wrote:
> $ zsh -c '{echo foo >&$fd;} {fd}> a'
> zsh:1: parse error near `{'
> (same for while/do/done constructs at least)
>
> Is that the expected behavior? I can't see it being documented.
It is documented now. This is all complicated stuff with wide
implications for the parser; there's is no chance I will have to time to
change it myself.
> That would be useful in
>
> while read <&$fd var; do
> ...
> done {fd}< file
>
> to avoid having to worry about overriding fds 3-9.
There's no code automatically to close file descriptors anyway.
Generally, that syntax isn't doing quite what the use of redirection
syntax would suggest; it's permanently opening a file descriptor, not
performing a possibly temporary redirection. You need to do:
local fd
{
exec {fd}<file
while read; do
...
done <&$fd
} always {
exec {fd}<&-
}
(although in this particular case there's nothing to stop you doing
while read var; do
...
done <file
but I presume you have something more complicated in mind.)
--
Peter Stephenson <p.w.stephenson@ntlworld.com>
Web page now at http://homepage.ntlworld.com/p.w.stephenson/
next prev parent reply other threads:[~2011-09-14 19:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-14 17:21 Stephane Chazelas
2011-09-14 17:36 ` Mikael Magnusson
2011-09-14 19:06 ` Peter Stephenson [this message]
2011-09-14 19:31 ` Stephane Chazelas
2011-09-14 21:05 ` Peter Stephenson
2011-09-15 12:58 ` Stephane Chazelas
2011-09-15 13:09 ` Peter Stephenson
2011-09-15 13:22 ` Chet Ramey
2011-09-15 14:21 ` Stephane Chazelas
2011-09-17 12:21 ` Stephane Chazelas
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