by priority and version install. That is, if there are multiple
packages with the same name, then pick the package with the highest
priority, and only use the version if there are multiple packages
with the same priority.
This makes it possible to mark specific versions/variant in Nixpkgs
more or less desirable than others. A typical example would be a
beta version of some package (e.g., "gcc-4.2.0rc1") which should not
be installed even though it is the highest version, except when it
is explicitly selected (e.g., "nix-env -i gcc-4.2.0rc1").
* Idem for nix-env -u, only the semantics are a bit trickier since we
also need to take into account the priority of the currently
installed package (we never upgrade to a lower priority, unless
--always is given).
a user environment by an install or upgrade action. This is
particularly useful if you have a version installed that you don't
want to upgrade (e.g., because the newer versions are broken).
Example:
$ nix-env -u zapping --dry-run
(dry run; not doing anything)
upgrading `zapping-0.9.6' to `zapping-0.10cvs6'
$ nix-env --set-flag keep true zapping
$ nix-env -u zapping --dry-run
(dry run; not doing anything)
However, "-e" will still uninstall the package. (Maybe we should
require the keep flag to be explicitly set to false before it can be
uninstalled.)
to show only those derivations whose output is already in the Nix
store or that can be substituted (i.e., downloaded from somewhere).
In other words, it shows the packages that can be installed “quickly”,
i.e., don’t need to be built from source.
evaluator. This was important because the NixOS expressions started
to hit 2 MB default stack size on Linux.
GCC is really dumb about stack space: it just adds up all the local
variables and temporaries of every scope into one huge stack frame.
This is really bad for deeply recursive functions. For instance,
every `throw Error(format("error message"))' causes a format object
of a few hundred bytes to be allocated on the stack. As a result,
every recursive call to evalExpr2() consumed 4680 bytes. By
splitting evalExpr2() and by moving the exception-throwing code out
of the main functions, evalExpr2() now only consumes 40 bytes.
Similar for evalExpr().
which paths specified on the command line are invalid (i.e., don't
barf when encountering an invalid path, just print it). This is
useful for build-remote.pl to figure out which paths need to be
copied to a remote machine. (Currently we use rsync, but that's
rather inefficient.)
--export' into the Nix store, and optionally check the cryptographic
signatures against /nix/etc/nix/signing-key.pub. (TODO: verify
against a set of public keys.)
path. This is like `nix-store --dump', only it also dumps the
meta-information of the store path (references, deriver). Will add
a `--sign' flag later to add a cryptographic signature, which we
will use for exchanging store paths between build farm machines in a
secure manner.
attribute) about installed packages in user environments. Thus, an
operation like `nix-env -q --description' shows useful information
not only on available packages but also on installed packages.
* nix-env now passes the entire manifest as an argument to the Nix
expression of the user environment builder (not just a list of
paths), so that in particular the user environment builder has
access to the meta attributes.
* New operation `--set-flag' in nix-env to change meta info of
installed packages. This will be useful to pass per-package
policies to the user environment builder (e.g., how to resolve
collision or whether to disable a package (NIX-80)) or upgrade
policies in nix-env (e.g., that a package should be "masked", that
is, left untouched by upgrade actions). Example:
$ nix-env --set-flag enabled false ghc-6.4
computing the store path (NIX-77). This is an important security
property in multi-user Nix stores.
Note that this changes the store paths of derivations (since the
derivation aterms are added using addTextToStore), but not most
outputs (unless they use builtins.toFile).
* `sub' to subtract two numbers.
* `stringLength' to get the length of a string.
* `substring' to get a substring of a string. These should be enough
to allow most string operations to be expressed.
programs, so if a builder uses TMPDIR, then it will fail when
executed through nix-setuid-helper. In fact Glibc clears a whole
bunch of variables (see sysdeps/generic/unsecvars.h in the Glibc
sources), but only TMPDIR should matter in practice. As a
workaround, we reinitialise TMPDIR from NIX_BUILD_TOP.
important to get garbage collection to work if there is any
inconsistency in the database (because the referrer table is used to
determine whether it is safe to delete a path).
* `nix-store --verify': show some progress.
* nix-unpack-closure: extract the top-level paths from the closure and
print them on stdout. This allows them to be installed, e.g.,
"nix-env -i $(nix-unpack-closure)". (NIX-64)
