Re: Memory-efficient way of opening large files in Emacs read-only

[Marcin Borkowski <mbork@mbork.pl>]

On 2022-12-08, at 03:49, Mikhail Pomaznoy <mikpom@mikpom.ru> wrote:

> Greetings!
>
> In my daily workflows I commonly stumble upon a task of peeking into
> a header of a large (sometimes compressed) file. Those files can
> commonly be gigabytes in compressed form so can't fit into
> memory. I was wondering how can this be done in Emacs to leverage its
> search and navigate capabilities?
>
> In a terminal this task is nicely accomplished with `less`, which
> loads file on demand while you scroll (memory-efficiently) and
> automatically detects at least gzip compression. However I am
> struggling to do something similar in Emacs for quite a long time.
> I tried VLF (requires manually switching chunks loaded, encountered
> problems with compression), view-file (loads everything in memory),
> running less in Emacs terminals (I prefer outside-Emacs terminals) but
> for various reasons all this solutions are suboptimal and I usually
> end up with using `less`.
>
> Is there something in Emacs I am missing? Is something like this makes
> sense to develop (I consider to write something for Emacs) ? I am
> using Emacs 28 and maybe in Emacs 29 there are novelties related to
> this issue?

I have no idea if Emacs has anything like this (I doubt), but the way
I'd go about it would be to either leverage `less' inside one of the
Emacs terminals or write some Elisp, colling to things like `gunzip' and
`head' and then putting the result into some buffer.  (I think you could
even make it so that scrolling down would load the next portion in the
background, à la modern Web.  While I /hate/ this behavior of websites,
here it could actually make sense.)

Best,

-- 
Marcin Borkowski
http://mbork.pl