Date: Sat, 21 Apr 2001 14:06:04 +0100 From: Brian Somers <brian@Awfulhak.org> To: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net> Cc: bsd@bsdhome.com (Brian Dean), schweikh@schweikhardt.net (Jens Schweikhardt), freebsd-current@FreeBSD.ORG, brian@Awfulhak.org Subject: Re: cp -d dir patch for review (or 'xargs'?) Message-ID: <200104211306.f3LD64543456@hak.lan.Awfulhak.org> In-Reply-To: Message from "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net> of "Fri, 20 Apr 2001 21:00:56 PDT." <200104210400.VAA69212@gndrsh.dnsmgr.net>
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> > On Fri, Apr 20, 2001 at 07:26:18PM -0700, Rodney W. Grimes wrote:
> >
> > > > (cat bigfilelist; echo destdir) | xargs cp
> > >
> > > I like this version of the patch!! It's much much cleaner than
> > > hacking up cp or xargs, it even follows the unix principle of
> > > using simple tools and glueing them togeather to do bigger
> > > jobs, is unix implementation independent, and is very clear
> > > in what it does.
> >
> > It's clean, simple, and unfortunately, totally bogus.
> >
> > Try:
> >
> > echo 1 2 3 4 5 6 7 8 9 | xargs -n 4 echo
> >
> > Now consider what would happen with the above suggested construct with
> > a very long file list.
>
> bleck... try this for your sample:
> $ (echo 1 2 3 4 5 6 7 8 9 | xargs -n 4) | while read x; do
> > echo -n $x; echo " dst"
> > done
> 1 2 3 4 dst
> 5 6 7 8 dst
> 9 dst
> $
>
> >
> > I don't see a problem with adding an option to cp to treat the first
> > argument as the target instead of the last argument. It's a simple
> > solution, the code change is simple, and it produces the exact desired
> > result. What's the problem?
>
> It's yet another non-portable option.
I hate to appear rude, but has anybody in this discussion actually used
xargs for what it's meant to be used ?
How do you do this in a script:
cd /topdir; find . -type f | xargs -i {} cp {} /otherdir/.
Before anyone starts writing scripts, consider that {} will be
replaced by xargs with (roughly) ARG_MAX - 10 characters worth of the
stuff coming off the pipe. If your combined arguments plus
environment exceeds ARG_MAX execve(2) will give you E2BIG.
> --
> Rod Grimes - KD7CAX @ CN85sl - (RWG25) rgrimes@gndrsh.dnsmgr.net
--
Brian <brian@Awfulhak.org> <brian@[uk.]FreeBSD.org>
<http://www.Awfulhak.org>; <brian@[uk.]OpenBSD.org>
Don't _EVER_ lose your sense of humour !
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