Release 1.7 (2014-04-11)
In addition to the usual bug fixes, this release has the following new features:
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Antiquotation is now allowed inside of quoted attribute names (e.g. set."${foo}"). In the case where the attribute name is just a single antiquotation, the quotes can be dropped (e.g. the above example can be writtenset.${foo}). If an attribute name inside of a set declaration evaluates tonull(e.g.{ ${null} = false; }), then that attribute is not added to the set.
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Experimental support for cryptographically signed binary caches. See the commit for details. 
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An experimental new substituter, download-via-ssh, that fetches binaries from remote machines via SSH. Specifying the flags--option use-ssh-substituter true --option ssh-substituter-hosts user@hostnamewill cause Nix to download binaries from the specified machine, if it has them.
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nix-store -randnix-buildhave a new flag,--check, that builds a previously built derivation again, and prints an error message if the output is not exactly the same. This helps to verify whether a derivation is truly deterministic. For example:$ nix-build '<nixpkgs>' -A patchelf … $ nix-build '<nixpkgs>' -A patchelf --check … error: derivation `/nix/store/1ipvxs…-patchelf-0.6' may not be deterministic: hash mismatch in output `/nix/store/4pc1dm…-patchelf-0.6.drv'
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The nix-instantiateflags--eval-onlyand--parse-onlyhave been renamed to--evaland--parse, respectively.
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nix-instantiate,nix-buildandnix-shellnow have a flag--expr(or-E) that allows you to specify the expression to be evaluated as a command line argument. For instance,nix-instantiate --eval -E '1 + 2'will print3.
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nix-shellimprovements:- 
It has a new flag, --packages(or-p), that sets up a build environment containing the specified packages from Nixpkgs. For example, the command$ nix-shell -p sqlite xorg.libX11 hellowill start a shell in which the given packages are present. 
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It now uses shell.nixas the default expression, falling back todefault.nixif the former doesn’t exist. This makes it convenient to have ashell.nixin your project to set up a nice development environment.
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It evaluates the derivation attribute shellHook, if set. Sincestdenvdoes not normally execute this hook, it allows you to donix-shell-specific setup.
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It preserves the user’s timezone setting. 
 
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In chroots, Nix now sets up a /devcontaining only a minimal set of devices (such as/dev/null). Note that it only does this if you don’t have/devlisted in yourbuild-chroot-dirssetting; otherwise, it will bind-mount the/devfrom outside the chroot.Similarly, if you don’t have /dev/ptslisted inbuild-chroot-dirs, Nix will mount a privatedevptsfilesystem on the chroot’s/dev/pts.
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New built-in function: builtins.toJSON, which returns a JSON representation of a value.
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nix-env -qhas a new flag--jsonto print a JSON representation of the installed or available packages.
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nix-envnow supports meta attributes with more complex values, such as attribute sets.
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The -Aflag now allows attribute names with dots in them, e.g.$ nix-instantiate --eval '<nixos>' -A 'config.systemd.units."nscd.service".text'
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The --max-freedoption tonix-store --gcnow accepts a unit specifier. For example,nix-store --gc --max-freed 1Gwill free up to 1 gigabyte of disk space.
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nix-collect-garbagehas a new flag--delete-older-thanNd, which deletes all user environment generations older than N days. Likewise,nix-env --delete-generationsaccepts a Ndage limit.
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Nix now heuristically detects whether a build failure was due to a disk-full condition. In that case, the build is not flagged as “permanently failed”. This is mostly useful for Hydra, which needs to distinguish between permanent and transient build failures. 
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There is a new symbol __curPosthat expands to an attribute set containing its file name and line and column numbers, e.g.{ file = "foo.nix"; line = 10; column = 5; }. There also is a new builtin function,unsafeGetAttrPos, that returns the position of an attribute. This is used by Nixpkgs to provide location information in error messages, e.g.$ nix-build '<nixpkgs>' -A libreoffice --argstr system x86_64-darwin error: the package ‘libreoffice-4.0.5.2’ in ‘.../applications/office/libreoffice/default.nix:263’ is not supported on ‘x86_64-darwin’
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The garbage collector is now more concurrent with other Nix processes because it releases certain locks earlier. 
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The binary tarball installer has been improved. You can now install Nix by running: $ bash <(curl -L https://nixos.org/nix/install)
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More evaluation errors include position information. For instance, selecting a missing attribute will print something like error: attribute `nixUnstabl' missing, at /etc/nixos/configurations/misc/eelco/mandark.nix:216:15
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The command nix-setuid-helperis gone.
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Nix no longer uses Automake, but instead has a non-recursive, GNU Make-based build system. 
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All installed libraries now have the prefix libnix. In particular, this gets rid oflibutil, which could clash with libraries with the same name from other packages.
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Nix now requires a compiler that supports C++11. 
This release has contributions from Danny Wilson, Domen Kožar, Eelco Dolstra, Ian-Woo Kim, Ludovic Courtès, Maxim Ivanov, Petr Rockai, Ricardo M. Correia and Shea Levy.