[Nix-dev] weird garbage output inside nix-shell

[Roni Choudhury]

On Sun, Jun 11, 2017 at 5:45 AM Sergiu Ivanov sivanov at colimite.fr
<http://mailto:sivanov@colimite.fr> wrote:

Thus quoth  Roni Choudhury  at 17:38 on Sat, Jun 10 2017:
> >
> > Linus, Sam, and Sergiu - thank you for the suggestions. I did poke
> > around in the output from `env` and discovered IN_NIX_SHELL, and
> > arranged my .zshrc to show `${name}` when `$IN_NIX_SHELL` is
> > true. Fantastic!
>
> Great job!  I didn't know about that environment variable.
>
I think it should be called NIX_IN_SHELL but IN_NIX_SHELL is good too :).

> I'm not sure the other problem has to do with character encodings
> > (though I don't know too much about how that works).
>
> Ooh, sorry, I messed up in my previous E-mail by saying "ASCII terminal
> codes" :-( What I really meant was this:
>
>   https://en.wikipedia.org/wiki/ANSI_escape_code

Ah ok. Well, I use terminal colors in my zsh setup so I can’t imagine it’s
a misinterpreted escape code…

> I did notice that `ldd $(which vim)` shows me different results when I
> > am inside my nix-shell vs. when I'm not.
>
> This is weird.  I get exactly the same results (modulo the differences
> in the memory map addresses listed in parentheses at the end of each
> line).  (I don't have vim mentioned in this particular shell.nix.)
>
Definitely weird then - is there some way to probe exactly what packages
are in my nix-shell environment? Do I do that just by following symlinks
eventually into the store?

> I kind of thought I shouldn't even be able to launch vim from inside
> > my shell if it's not listed as a buildDep.
>
> It looks to me that nix-shell _extends_ the environment it is run in.
> So, if you run nix-shell in an environment which contains vim, you have
> vim inside nix-shell.
>
Right, my mistake. Then I’m starting to think it’s that weird shifting of
dynamic libraries that’s causing my shell trouble. In fact, see below…

> If I send my shell.nix, would someone else mind trying to use it to see if
> > you can reproduce my strange results?
>
> Go ahead.  (Remember to scrub all sensitive information.)
>
Thank you. I’ve attached my shell.nix file to this message.

I did discover that I can “fix” my shell problems by omitting this line
from shell.nix:

LD_LIBRARY_PATH = stdenv.lib.makeLibraryPath libs;

Without that line, my LD_LIBRARY_PATH env var just has
/run/opengl-driver/lib in it, and vim works as expected. I’m not sure why I
did this, because my build seems to work without it. This may explain why
my ldd output differs inside and outside my nix-shell environment.

So I guess my next question is: if I did want to put those packages’
libraries into my library loader path, how am I supposed to do it? I tried
this:

LD_LIBRARY_PATH = "$LD_LIBRARY_PATH:${stdenv.lib.makeLibraryPath libs}";

but that doesn’t work for, perhaps, obvious reasons.

Thanks for the help on this!!

roni
​
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