[Nix-dev] string vs path hell

[Kirill Elagin]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
let lib = (import <nixpkgs> {}).lib;
    exe = {
      foo = "/some/path/to/foo";
      bar = "/other/path/to/bar";
    };
in
{
  contents =
    map (v :
      let
        takeFileName = p :
          let fl = lib.splitString "/" p; in lib.last fl;
        fn = takeFileName "${v}";
        dummy = takeFileName "/a/string/encoded/path/dummy";
      in

        #builtins.trace fn
        #builtins.trace dummy

        {
          symlink = "/bin/${fn}";
          object = v;
        }) (lib.attrValues exe);
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~~~~~~
nix-repl> :l test.nix
Added 1 variables.

nix-repl> :p contents
[ { object = "/other/path/to/bar"; symlink = "/bin/bar"; } { object =
"/some/path/to/foo"; symlink = "/bin/foo"; } ]
~~~~~~~~~~~~~~~~~

Dunno, you should probably inspect your `exe` set closer in case
something's wrong with values there.


--
Кирилл Елагин


On Tue, Jun 10, 2014 at 10:41 AM, Sergey Mironov <grrwlf at gmail.com> wrote:

> OK, you are right. My code snippet really works fine. So I feel I must
> post a part of my real code which still doesn't work for me. It is a
> bit long, but maybe you will be able to help me find a mistake. Here
> it is (below). This expression takes a set of paths to the executables
> (exe // setuids) and builds the initrd image. Every attribute of (exe
> // setuids) is either a string like [adduser =
> "${busybox}/sbin/adduser";] or the result of mkDerivation producing
> the single binary in it's $out.
>
> Note the "dummy" expression. If I uncomment "builtins.trace dummy"
> line, it will show me the expected result (string "dummy" for every
> list item). But in the same time, "builtins.trace fn" shows that fn is
> evaluated incorrectly. Every time it contains full Nix path
> ("/nix/strote/...", see example at the end of the letter) instead of
> the filename part. It looks like 'splitString' doesn't recognize it's
> argument as a string.
>
> Please, comment!
> Sergey
>
>
> --
> the code
>
>       ...
>
>       img = makeInitrd {
>
>         compressor = "${gzip}/bin/gzip --fast";
>
>         contents = with all.ipkgs;
>           [{ symlink = "/init";
>             object = exe.init;
>           }
>           { symlink = "/bin/sh";
>             object = exe.shell;
>           }] ++
>           map (v :
>
>             let
>
>               takeFileName = p : let
>                   fl = lib.splitString "/" p;
>                 in lib.last fl;
>
>               fn = takeFileName "${v}";
>
>               dummy = takeFileName "/a/string/encoded/path/dummy";
>
>             in
>
>             # builtins.trace fn   # <---------------- see example output
> below
>             # builtins.trace dummy
>
>             {
>               symlink = "/bin/${fn}";
>               object = v;
>             }) (lib.attrValues (exe // setuids));
>       };
>
> --
> example output of "builtins.trace fn":
>
> trace:
> /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/sbin/addgroup
> trace:
> /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/sbin/adduser
> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/false
> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/true
> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/awk
> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/cat
> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/chmod
> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/chown
> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/cp
> trace: /nix/store/h8rs91fjivsh6wakmwmpkca31wfp38g0-msr-tools-1.3/bin/cpuid
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.science.uu.nl/pipermail/nix-dev/attachments/20140610/2e7a8988/attachment-0001.html