Date: Sat, 21 Apr 2001 16:51:24 +0200 (CEST) From: Oliver Fromme <olli@secnetix.de> To: freebsd-current@FreeBSD.ORG Subject: Re: cp -d dir patch for review (or 'xargs'?) Message-ID: <200104211451.QAA04891@lurza.secnetix.de> In-Reply-To: <93802.987862964@axl.fw.uunet.co.za>
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Sheldon Hearn <sheldonh@uunet.co.za> wrote:
> On Sat, 21 Apr 2001 14:06:04 +0100, Brian Somers wrote:
> > How do you do this in a script:
> >
> > cd /topdir; find . -type f | xargs -i {} cp {} /otherdir/.
>
> for i in `find /path/to/source -type f`; do
> cp $i /path/to/dest/
> done
That can overflow your shell's command line limit (at the
"for" command). True, our /bin/sh doesn't has such a
limit, AFAIK, but there _are_ shells that do). Apart from
that it is extremely inefficient, because it runs a "cp"
for every single file. These are exactly the problems that
xargs is supposed to solve.
Actually I don't see any problem with Brian's approach
(provided that the -i option exists, of course).
xargs _does_ take the size of the environment into account,
as well as the size of all arguments, and it still leaves
much room (it only uses up to ARG_MAX - 2048 by default).
Oh by the way, in this particular example it is probably a
good idea to use cpio. This will even work with our xargs
(which doesn't support -i yet):
cd /topdir; find . -type f | cpio -dup /otherdir
should do exactly that job.
Regards
Oliver
--
Oliver Fromme, secnetix GmbH & Co KG, Oettingenstr. 2, 80538 München
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