Re: Using :g to filter lines through an external command

On Sun, 12 Jul 2020 at 19:12, Tim Chase <vim@tim.thechases.com> wrote:
>
> On 2020-07-12 09:59, A. Wik wrote:
> > Hi all,
> >
> > Assume I have a file (or just a buffer) with the contents:
> > echo Hello from /bin/sh
> > test1
> > test2
> > test3
> > ---end-file---
>
> Well, for this particular buffer, you're processing the whole file so
> you could just use
>
> :%!nl
>
> which will do what you want.

2,$!nl actually -- there's an "echo" line first.

> you might do something like
>
> :g/^test/.,/^\(test\)\@!/-!nl
>
> which looks for lines starting with "test" then, starting a range
> there ('.') through (',') the line before ('-') the next line that
> doesn't start with "test" ("/^\(test\)\@!/"), runs each of those
> ranges through nl(1)

That is an improvement.

> If you want nl(1) to jump gaps across disjoint ranges, you'll have to
> change strategy. I'd use vim's in-built expression-evaluation:
>
> :let i=0 | g/^test/let i+=1 | s/^/\=i.' '

Good.

You can use an external program to do the work; eg:
:%!awk 'BEGIN { i=1 } /^test/ { printf "\%d \%s\n", i++, $0; next; }
{ print $0 }'

What is the best way for collecting the output of :g? This works:
:g/^test/.w! >> test.tmp
But it does require a temporary file. Why is the dot required?
Leaving it out produces a test.tmp containing several repetitions of
the whole source file.

:let @a = "" | g/^test/y A
also works, but it puts an empty line first and last in the A
register; of course, deleting them is easy enough.

:v/^test/d
works too; you can use undo to get the other lines back.

:let @a="" | redir @A | g/^test/
:redir END
produces an A register like the "y A" above, with a blank line at the
start and end.

-aw

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