`-u'. Instead of acquiring an exclusive lock on the profile for the
entire duration of the operation, we just perform the operation
optimistically (without an exclusive lock), and check at the end
whether the profile changed while we were busy (i.e., the symlink
target changed). If so, the operation is restarted. Restarting is
generally cheap, since the build results are still in the Nix store.
Most of the time, only the user environment has to be rebuilt.
again. (After the previous substituter mechanism refactoring I
didn't update the code that obtains the references of substitutable
paths.) This required some refactoring: the substituter programs
are now kept running and receive/respond to info requests via
stdin/stdout.
it only does something if $NIX_OTHER_STORES (not really a good
name...) is set.
* Do globbing on the elements of $NIX_OTHER_STORES. E.g. you could
set it to /mnts/*/nix or something.
* Install substituters in libexec/nix/substituters.
logic through the `parseDrvName' and `compareVersions' primops.
This will allow expressions to easily check whether some dependency
is a specific needed version or falls in some version range. See
tests/lang/eval-okay-versions.nix for examples.
bytes have been freed, `--max-links' to stop when the Nix store
directory has fewer than N hard links (the latter being important
for very large Nix stores on filesystems with a 32000 subdirectories
limit).
store under the reference relation, since that means that the
garbage collector will need a long time to start deleting paths.
Instead just delete the referrers of a path first.
This isn't usually a problem, except that it causes tests to fail
when performed in a directory with a very long path name. So chdir
to the socket directory and use a relative path name.
/tmp/nix-<pid>-<counter> for temporary build directories. This
increases purity a bit: many packages store the temporary build path
in their output, causing (generally unimportant) binary differences.
undefined variables by definition. This matters for the
implementation of "with", which does a call to checkVarDefs to see
if the body of the with has no undefined variables. (It can't be
checked at parse time because you don't know which variables are in
the "with" attribute set.) If we check closed terms, then we check
not just the with body but also the substituted terms, which are
typically very large. This is the cause of the poor nix-env
performance on Nixpkgs lately. It didn't happen earlier because
"with" wasn't used very often in the past.
This fix improves nix-env performance roughly 60x on current Nixpkgs.
nix-env -qa is down from 29.3s to 0.5s on my laptop, and nix-env -qa
--out-path is down from 229s to 3.39s. Not bad for a 1-line fix :-)
single quotes. Example (from NixOS):
job = ''
start on network-interfaces
start script
rm -f /var/run/opengl-driver
${if videoDriver == "nvidia"
then "ln -sf ${nvidiaDrivers} /var/run/opengl-driver"
else if cfg.driSupport
then "ln -sf ${mesa} /var/run/opengl-driver"
else ""
}
rm -f /var/log/slim.log
end script
'';
This style has two big advantages:
- \, ' and " aren't special, only '' and ${. So you get a lot less
escaping in shell scripts / configuration files in Nixpkgs/NixOS.
The delimiter '' is rare in scripts (and can usually be written as
""). ${ is also fairly rare.
Other delimiters such as <<...>>, {{...}} and <|...|> were also
considered but this one appears to have the fewest drawbacks
(thanks Martin).
- Indentation is intelligently stripped so that multi-line strings
can follow the nesting structure of the containing Nix
expression. E.g. in the example above 6 spaces are stripped from
the start of each line. This prevents unnecessary indentation in
generated files (which sometimes even breaks things).
See tests/lang/eval-okay-ind-string.nix for some examples.
$ nix-env -e $(which firefox)
or
$ nix-env -e /nix/store/nywzlygrkfcgz7dfmhm5xixlx1l0m60v-pan-0.132
* nix-env -i: if an argument contains a slash anywhere, treat it as a
path and follow it through symlinks into the Nix store. This allows
things like
$ nix-build -A firefox
$ nix-env -i ./result
* nix-env -q/-i/-e: don't complain when the `*' selector doesn't match
anything. In particular, `nix-env -q \*' doesn't fail anymore on an
empty profile.
