Date: Fri, 5 Mar 2021 18:33:14 -1000 From: "parv/freebsd" <parv.0zero9+freebsd@gmail.com> To: Gary Aitken <freebsd@dreamchaser.org> Cc: freebsd-questions@freebsd.org Subject: Re: sed -i empty argument compatibility issue Message-ID: <CABObuOrJ3QC==ioq=1Z7Sjh=f-VjwThhnNBYYUAJrwXOTEmMoQ@mail.gmail.com> In-Reply-To: <606b8bfa-4fe5-883a-d7ac-99f41655f728@dreamchaser.org> References: <9178f6c5-631a-c2c2-c6b1-8def94a3397b@dreamchaser.org> <20210305142352297368817@bob.proulx.com> <606b8bfa-4fe5-883a-d7ac-99f41655f728@dreamchaser.org>
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On Fri, Mar 5, 2021 at 5:56 PM Gary Aitken wrote:
> On 3/5/21 2:43 PM, Bob Proulx wrote:
> > Gary Aitken wrote:
> >> I'm trying to come up with a fix for a script in a port which
> >> invokes sed. The port comes from a linux environment, and the
> >> offending line looks like this:
...
> In order to port this then _something_ must be changed. As to what
> > must be changed that is up to you and judegement and the larger view
> > of everything in your environment. But off the top of my head these
> > different possibilities come to mind.
> >
> > 1. Edit the script and change this to that. This makes it run on
> > FreeBSD sed. Of course then this does not work the other direction.
> >
> > -COMMAND sed -i "/^# /d" "${outfile}" +COMMAND sed -i "" "/^# /d"
> > "${outfile}"
> >
> > 2. Use perl. Change that edit command to be this. This should work
> > the same everywhere that has perl. It does create a dependency upon
> > perl that might not have been present before.
> >
> > perl -i -lpe 'next if /^# /' "${outfile}"
>
I like it!
> > 3. Avoid -i and use a temporary file, just like in the old days.
> > However this introduces the need for temporary file handling. But
> > maybe that isn't important here.
> >
> > sed "/^# /d" "${outfile}" > "$tmpfile" && mv "$tmpfile" "${outfile}"
>
This won't do, when ...
> 4. Introduce a "sed" wrapper in PATH that intercepts the call to the
> > real sed, detects this problematic usage case, and then DTRT does
> > the right thing with it. This wrapper could have all of the correct
> > temporary file handling needed to make this work.
>
...
#!/bin/sh
# Set sed path & -i option based on "uname -a" output.
SED=
host_type=$( uname -a )
case "${host_type}" in
*Linux* )
SED="/usr/bin/sed -i''"
;;
*FreeBSD* )
SED="/usr/bin/sed -i ''"
;;
esac
# Set $@ to contain original arguments prefixed by sed with -i option.
set -- ${SED} $@
# Now run the sed with the arguments given.
$@
> 6. Compile GNU sed locally and install it in PATH earlier. This
> > would probably be a generally good option globally. However it's
> > possible you might run into portability problems in the reverse
> > case.
>
If GNU sed could be installed, this would be most agreeable.
I prefer to use the absolute path to remove ambiguity about the kind of
sed being used, especially in the above case.
- parv
Thanks for the list. That's two more than I came up with. I'm
> inclined to #2 (which I hadn't thought of) or #3.
>
--
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