Re: Append newline to many files

[Mikael Magnusson <mikachu@xxxxxxxxx>]

On 9/26/22, Dominik Vogt <dominik.vogt@xxxxxx> 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@xxxxxx>
>> > 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