* Documented indented string literals.
* Release notes.
This commit is contained in:
Eelco Dolstra
parent
de012e76e2
commit
59707975a3
3 changed files with 193 additions and 43 deletions
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@ -486,7 +486,7 @@ removeAttrs { x = 1; y = 2; z = 3; } ["a" "x" "z"]</screen>
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</varlistentry>
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<varlistentry><term><function>builtins.substr</function>
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<varlistentry><term><function>builtins.substring</function>
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<replaceable>start</replaceable> <replaceable>len</replaceable>
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<replaceable>s</replaceable></term>
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@ -8,20 +8,31 @@
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<!--==================================================================-->
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<section xml:id="ssec-relnotes-0.11"><title>Release 0.11 (TBA)</title>
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<section xml:id="ssec-relnotes-0.11"><title>Release 0.11 (December 31,
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2007)</title>
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<para>The most important improvement in Nix 0.11 is secure multi-user
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support. It also features many usability improvements and language
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extensions, many of them to support NixOS. Here is an (incomplete)
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list:</para>
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<itemizedlist>
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<listitem><para>TODO: multi-user support. The old setuid method for
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sharing a store between multiple users has been
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removed.</para></listitem>
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<listitem><para>Secure multi-user support. A single Nix store can
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now be shared between multiple (possible untrusted) users. This is
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an important feature for NixOS, where it allows non-root users to
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install software. The old setuid method for sharing a store between
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multiple users has been removed. Details for setting up a
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multi-user store can be found in the manual.</para></listitem>
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<listitem><para>The new command <command>nix-copy-closure</command>
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gives you an easy and efficient way to exchange software between
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machines. It copies the missing parts of the closure of a set of
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store path to or from a remote machine.</para></listitem>
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store path to or from a remote machine via
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<command>ssh</command>.</para></listitem>
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<listitem><para><command>nix-prefetch-url</command> now by default
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@ -47,15 +58,21 @@
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for booting Linux don’t have any dependencies.</para></listitem>
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<!--
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<listitem><para>TODO: semantic cleanups of string concatenation
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etc. (mostly in r6740).</para></listitem>
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-->
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<listitem><para>TODO: now using Berkeley DB 4.5.</para></listitem>
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<listitem><para>Nix now uses Berkeley DB 4.5. The database is
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upgraded automatically, but you should be careful not to use old
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versions of Nix that still use Berkeley DB 4.4.</para></listitem>
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<!-- foo
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<listitem><para>TODO: option <option>- -reregister</option> in
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<command>nix-store - -register-validity</command>.</para></listitem>
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-->
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<listitem><para>The new attribute
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@ -65,32 +82,80 @@
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populated with the closure of certain paths.</para></listitem>
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<listitem><para>TODO: option <option>--max-silent-time</option>,
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configuration setting
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<literal>build-max-silent-time</literal>.</para></listitem>
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<listitem><para>The option <option>--max-silent-time</option>
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(corresponding to the configuration setting
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<literal>build-max-silent-time</literal>) allows you to set a
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timeout on builds — if a build produces no output on
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<literal>stdout</literal> or <literal>stderr</literal> for the given
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number of seconds, it is terminated. This is useful for recovering
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automatically from builds that are stuck in an infinite
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loop.</para></listitem>
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<listitem><para>TODO: <command>nix-env</command>
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<option>--set</option>.</para></listitem>
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<listitem><para><command>nix-env</command> <option>--set</option>
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modifies the current generation of a profile so that it contains
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exactly the specified derivation, and nothing else. For example,
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<literal>nix-env -p /nix/var/nix/profiles/browser --set
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firefox</literal> lets the profile named
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<filename>browser</filename> contain just Firefox.</para></listitem>
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<listitem><para>TODO: <option>--argstr</option>.</para></listitem>
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<listitem><para>The new <option>--argstr</option> (in
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<command>nix-env</command>, <command>nix-instantiate</command> and
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<command>nix-build</command>) is like <option>--arg</option>, except
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that the value is a string. For example, <literal>--argstr system
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i686-linux</literal> is equivalent to <literal>--arg system
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\"i686-linux\"'</literal> (note that <option>--argstr</option>
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prevents annoying quoting around shell arguments).</para></listitem>
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<listitem><para>TODO: <command>nix-env</command> now maintains meta
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info about installed packages in user environments. <option>-q
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--xml --meta</option> to show all meta info.</para></listitem>
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<listitem><para><command>nix-env</command> now maintains
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meta-information about installed packages in profiles. The
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meta-information is the contents of the <varname>meta</varname>
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attribute of derivations, such as <varname>description</varname> or
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<varname>homepage</varname>. The command <literal>nix-env -q --xml
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--meta</literal> shows all meta-information.</para></listitem>
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<listitem><para>TODO: <command>nix-env</command>
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<option>--set-flag</option>. Specific flags:
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<literal>active</literal>, <literal>priority</literal>,
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<literal>keep</literal>.</para></listitem>
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<listitem><para><command>nix-env</command> now uses the
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<varname>meta.priority</varname> attribute of derivations to resolve
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filename collisions between packages. Lower priority values denote
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a higher priority. For instance, the GCC wrapper package and the
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Binutils package in Nixpkgs both have a file
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<filename>bin/ld</filename>, so previously if you tried to install
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both you would get a collision. Now, on the other hand, the GCC
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wrapper declares a higher priority than Binutils, so the former’s
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<filename>bin/ld</filename> is symlinked in the user
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environment.</para></listitem>
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<listitem><para>TODO: <command>nix-env</command> <option>-i</option>
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/ <option>-u</option> take package priorities into
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account.</para></listitem>
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<listitem><para><command>nix-env --set-flag</command> allows
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meta attributes of installed packages to be modified. There are
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several attributes that can be usefully modified, because they
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affect <command>nix-env</command> behaviour or the user environment
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build script:
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<itemizedlist>
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<listitem><para><varname>meta.priority</varname> can be changed
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to resolve filename clashes (see above).</para></listitem>
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<listitem><para><varname>meta.keep</varname> can be set to
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<literal>true</literal> to prevent the package from being
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upgraded or replaced. Useful if you want to hang on to an older
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version of a package. (This is similar to masking in
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Gentoo.)</para></listitem>
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<listitem><para><varname>meta.active</varname> can be set to
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<literal>false</literal> to “disable” the package. That is, no
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symlinks will be generated to the files of the package, but it
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remains part of the profile (so it won’t be garbage-collected).
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Set it back to <literal>true</literal> to re-enable the
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package.</para></listitem>
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</itemizedlist>
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</para></listitem>
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<listitem><para><command>nix-env -q</command> now has a flag
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@ -99,27 +164,36 @@
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output is already in the Nix store or that can be substituted (i.e.,
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downloaded from somewhere). In other words, it shows the packages
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that can be installed “quickly”, i.e., don’t need to be built from
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source. TODO: flag is also available in nix-env -i /
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-u.</para></listitem>
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source. The <option>-b</option> flag is also available in
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<command>nix-env -i</command> and <command>nix-env -u</command> to
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filter out derivations for which no pre-built binary is
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available.</para></listitem>
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<listitem><para>TODO: new built-ins
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<listitem><para>Several new built-in functions:
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<function>builtins.attrNames</function>,
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<function>builtins.filterSource</function>,
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<function>builtins.sub</function>,
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<function>builtins.isAttrs</function>,
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<function>builtins.isFunction</function>,
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<function>builtins.listToAttrs</function>,
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<function>builtins.stringLength</function>,
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<function>builtins.substring</function>.</para></listitem>
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<function>builtins.sub</function>,
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<function>builtins.substring</function>,
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<function>throw</function>,
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<function>builtins.trace</function>,
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<function>builtins.readFile</function>.</para></listitem>
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<listitem><para>TODO: each subscribed channel is its own attribute
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in the top-level expression generated for the channel, this allows
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disambiguation (<command>nix-env -qaA</command>).</para></listitem>
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<listitem><para><command>nix-channel</command>: each subscribed
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channel is its own attribute in the top-level expression generated
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for the channel. This allows disambiguation (e.g. <literal>nix-env
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-i -A nixpkgs_unstable.firefox</literal>).</para></listitem>
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<listitem><para>The substitutes table has been removed from the
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database. This makes operations such as <command>nix-pull</command>
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and <command>nix-channel --update</command>
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<emphasis>much</emphasis> faster.</para></listitem>
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and <command>nix-channel --update</command> much, much
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faster.</para></listitem>
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<listitem><para><command>nix-prefetch-url</command> now has a
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@ -128,11 +202,19 @@
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the channel hasn’t changed.</para></listitem>
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<listitem><para>TODO: chroot support.</para></listitem>
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<listitem><para>Nix can now perform builds in an automatically
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generated “chroot”. This prevents a builder from accessing stuff
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outside of the Nix store, and thus helps ensure purity. This is an
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experimental feature.</para></listitem>
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<listitem><para>TODO: <literal>''</literal>-style string
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literals.</para></listitem>
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<listitem><para>A new kind of string literal: strings between double
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single-quotes (<literal>''</literal>) have indentation
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“intelligently” removed. This allows large strings (such as shell
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scripts or configuration file fragments in NixOS) to cleanly follow
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the indentation of the surrounding expression. It also requires
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much less escaping, since <literal>''</literal> is less common in
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most languages than <literal>"</literal>.</para></listitem>
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</itemizedlist>
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@ -612,7 +612,10 @@ language.</para>
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<listitem>
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<para><emphasis>Strings</emphasis> are enclosed between double
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<para><emphasis>Strings</emphasis> can be written in three
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ways.</para>
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<para>The most common way is to enclose the string between double
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quotes, e.g., <literal>"foo bar"</literal>. Strings can span
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multiple lines. The special characters <literal>"</literal> and
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<literal>\</literal> and the character sequence
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@ -658,8 +661,73 @@ configureFlags = "
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some of which in turn contain expressions (e.g.,
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<literal>${mesa}</literal>).</para>
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<para>As a convenience, <emphasis>URIs</emphasis> as defined in
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appendix B of <link
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<para>The second way to write string literals is as an
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<emphasis>indented string</emphasis>, which is enclosed between
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pairs of <emphasis>double single-quotes</emphasis>, like so:
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<programlisting>
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''
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This is the first line.
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This is the second line.
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This is the third line.
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''</programlisting>
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This kind of string literal intelligently strips indentation from
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the start of each line. To be precise, it strips from each line a
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number of spaces equal to the minimal indentation of the string as
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a whole (disregarding the indentation of empty lines). For
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instance, the first and second line are indented two space, while
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the third line is indented three spaces. Thus, two spaces are
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stripped from each line, so the resulting string is
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<programlisting>
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"This is the first line.\nThis is the second line.\n This is the third line.\n"</programlisting>
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</para>
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<para>Note that the whitespace and newline following the opening
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<literal>''</literal> is ignored if there is no non-whitespace
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text on the initial line.</para>
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<para>Antiquotation
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(<literal>${<replaceable>expr</replaceable>}}</literal>) is
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supported in indented strings.</para>
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<para>Since <literal>${</literal> and <literal>''</literal> have
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special meaning in indented strings, you need a way to quote them.
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<literal>${</literal> can be escaped by prefixing it with
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<literal>''</literal>, i.e., <literal>''${</literal>.
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<literal>''</literal> can be escaped by prefixing it with
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<literal>'</literal>, i.e., <literal>'''</literal>. Finally,
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linefeed, carriage-return and tab characters can be writted as
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<literal>''\n</literal>, <literal>''\r</literal>,
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<literal>''\t</literal>.</para>
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<para>Indented strings are primarily useful in that they allow
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multi-line string literals to follow the indentation of the
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enclosing Nix expression, and that less escaping is typically
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necessary for strings representing languages such as shell scripts
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and configuration files because <literal>''</literal> is much less
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common than <literal>"</literal>. Example:
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<programlisting>
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stdenv.mkDerivation {
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<replaceable>...</replaceable>
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postInstall =
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''
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mkdir $out/bin $out/etc
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cp foo $out/bin
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echo "Hello World" > $out/etc/foo.conf
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${if enableBar then "cp bar $out/bin" else ""}
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'';
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<replaceable>...</replaceable>
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}
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</programlisting>
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</para>
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<para>Finally, as a convenience, <emphasis>URIs</emphasis> as
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defined in appendix B of <link
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xlink:href='http://www.ietf.org/rfc/rfc2396.txt'>RFC 2396</link>
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can be written <emphasis>as is</emphasis>, without quotes. For
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instance, the string
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