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From: Mikael Magnusson <mikachu@gmail.com>
To: zsh-users@zsh.org
Subject: Re: Append newline to many files
Date: Mon, 26 Sep 2022 21:39:31 +0200	[thread overview]
Message-ID: <CAHYJk3QafKYkn5zEjANHE6DUHBLBaz-i_rz-mwUWdUgh3Fz_Lg@mail.gmail.com> (raw)
In-Reply-To: <YzFoAzgt7bPAXCQ1@gmx.de>

On 9/26/22, Dominik Vogt <dominik.vogt@gmx.de> wrote:
> On Mon, Sep 26, 2022 at 09:11:04AM +0100, zzapper wrote:
>>
>> On 25/09/2022 14:30, Roman Perepelitsa wrote:
>> > On Sun, Sep 25, 2022 at 3:21 PM Dominik Vogt <dominik.vogt@gmx.de>
>> > wrote:
>> > > Assume there are thousands of text files that are not terminated
>> > > with a newline.  I want to concatenate them all, but add the
>> > > missing newline between files.
>> > >
>> > > This works but takes ten times as much time as "cat foo.*".
>> > >
>> > >    for i in foo.*; do cat "$i"; echo; done > out
>> > >
>> > > I can't really think of a fast yet simple solution.
>> > This should work:
>> >
>> >      print >lf
>> >      files=(foo.*)
>> >      lf=(lf)
>> >      cat -- ${files:^^lf}
>> >      rm lf
>> >
>> This looks interesting but any chance of an explanation of how it works
>> for
>> us lesser mortals please?
>
> It first generates a file "lf" that contains only a newline and
> stores the filename in an array "lf", and the names of the files
> in question in an array "files".
>
> "${files:^^lf}" merges the two arrays in an interleaving fashion.
> The result is file.1 lf file.2 lf file.3 lf ... (The shorter array
> is repeated up to the other one's length).
>
> Quite clever solution, but a bit complicated.

And here's a oneliner version,
() { cat -- ${@[2,-1]:^^1} } =(echo) foo.*

-- 
Mikael Magnusson


      reply	other threads:[~2022-09-26 19:40 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-25 13:19 Dominik Vogt
2022-09-25 13:30 ` Roman Perepelitsa
2022-09-26  8:11   ` zzapper
2022-09-26  8:51     ` Dominik Vogt
2022-09-26 19:39       ` Mikael Magnusson [this message]

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