Date: Thu, 28 Oct 2010 08:11:48 -0700 From: Chip Camden <sterling@camdensoftware.com> To: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: [OT] writing filters in sh Message-ID: <20101028151148.GB73337@libertas.local.camdensoftware.com> In-Reply-To: <20101027212841.GA67716@guilt.hydra> References: <20101027212841.GA67716@guilt.hydra>
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Quoth Chad Perrin on Wednesday, 27 October 2010:
> I know that in sh you can get the contents out of files specified as
> command line arguments:
>=20
> while read data; do
> echo $data
> done <$@
>=20
> I know you can also get the contents of files from pipes and redirects:
>=20
> while read data; do
> echo $data
> done
>=20
> In Perl, you can use a single construct to do both and, unlike the first
> sh example, it can also take multiple filenames as arguments and
> effectively concatenate their contents:
>=20
> while (<>) {
> print $_;
> }
>=20
> I'm not exactly an *expert* in sh, in part because when things start
> getting "interesting" while I'm writing shell scripts I tend to just use
> a more robust language like Perl. Please let me know if there's some way
> to use a simple idiom like the Perl example to get the same results in
> sh.
>=20
> --=20
> Chad Perrin [ original content licensed OWL: http://owl.apotheon.org ]
Here's a way to do what you're wanting to do. Unfortunately, it isn't a
generalized, single construct:
#!/bin/sh
if [ $# -ge 1 ];then
exec cat $@ | $0
exit
fi
while read data; do
echo $data
done
My lame attempts to generalize the first paragraph into an alias,
function, or shell script have met with disappointment.
--=20
Sterling (Chip) Camden | sterling@camdensoftware.com | 2048D/3A978E4F
http://camdensoftware.com | http://chipstips.com | http://chipsquips=
.com
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