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

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---
>
> :1!sh does what I would expect: it passes "echo Hello from /bin/sh"
> as input to the shell, which executes the line as a command, and
> the line is replaced with "echo"'s output "Hello from /bin/sh".
>
> :g/test/!nl does not do what I expected (and wanted). Instead of
> piping the matched lines through the "nl" command, it appears to
> start an interactive shell.

That is nl(1) waiting for input. Sending an EOF (control+D) will
terminate it (note that because it gets invoked 3 times, one for each
line, you'll need to ^D 3x as well).

> :g/test/.!nl works better, but executes "nl" once for *each* of the
> matched lines, which are replaced with the following:
> 1 test1
> 1 test2
> 1 test3
> ---end-quote---
>
> Is there a solution to this?

Well, for this particular buffer, you're processing the whole file so
you could just use

:%!nl

which will do what you want.

However if you have disjoint ranges, you'll need to go a bit further.
If you want contiguous ranges like

test1
test2
not this one
test3
test4
not this one either

to be numbered

1 test1
2 test2
not this one
1 test3
2 test4
not this one either

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)

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.' '

(adjust formatting to taste).

-tim



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