Document multiple output support
This commit is contained in:
Eelco Dolstra
parent
b215b23e9e
commit
24d5875514
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@ -96,7 +96,7 @@ also <xref linkend="sec-common-options" />.</phrase></para>
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<variablelist>
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<varlistentry><term><option>--drv-link</option> <replaceable>drvlink</replaceable></term>
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<listitem><para>Add a symlink named
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<replaceable>drvlink</replaceable> to the store derivation
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produced by <command>nix-instantiate</command>. The derivation is
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@ -108,14 +108,14 @@ also <xref linkend="sec-common-options" />.</phrase></para>
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</varlistentry>
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<varlistentry><term><option>--add-drv-link</option></term>
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<listitem><para>Shorthand for <option>--drv-link</option>
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<filename>./derivation</filename>.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--no-out-link</option></term>
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<listitem><para>Do not create a symlink to the output path. Note
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that as a result the output does not become a root of the garbage
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collector, and so might be deleted by <command>nix-store
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@ -125,7 +125,7 @@ also <xref linkend="sec-common-options" />.</phrase></para>
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<varlistentry xml:id='opt-out-link'><term><option>--out-link</option> /
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<option>-o</option> <replaceable>outlink</replaceable></term>
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<listitem><para>Change the name of the symlink to the output path
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created from <filename>result</filename> to
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<replaceable>outlink</replaceable>.</para></listitem>
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@ -143,7 +143,7 @@ also <xref linkend="sec-common-options" />.</phrase></para>
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<variablelist>
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<varlistentry><term><option>--command</option> <replaceable>cmd</replaceable></term>
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<listitem><para>In the environment of the derivation, executeq the
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command <replaceable>cmd</replaceable> instead of the default
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interactive shell.</para></listitem>
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@ -151,7 +151,7 @@ also <xref linkend="sec-common-options" />.</phrase></para>
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</varlistentry>
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<varlistentry><term><option>--exclude</option> <replaceable>regexp</replaceable></term>
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<listitem><para>Do not build any dependencies whose store path
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matches the regular expression <replaceable>regexp</replaceable>.
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This option may be specified multiple times.</para></listitem>
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@ -190,6 +190,25 @@ $ ./pan/gui/pan
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</para>
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<para>If a derivation has multiple outputs,
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<command>nix-build</command> will build the default (first) output.
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You can also build all outputs:
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<screen>
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$ nix-build '<nixpkgs>' -A openssl.all
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</screen>
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This will create a symlink for each output named
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<filename>result-<replaceable>outputname</replaceable></filename>.
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The suffix is omitted if the output name is <literal>out</literal>.
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So if <literal>openssl</literal> has outputs <literal>out</literal>,
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<literal>bin</literal> and <literal>man</literal>,
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<command>nix-build</command> will create symlinks
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<literal>result</literal>, <literal>result-bin</literal> and
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<literal>result-man</literal>. It’s also possible to build a specific
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output:
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<screen>
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$ nix-build '<nixpkgs>' -A openssl.man
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</screen>
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This will create a symlink <literal>result-man</literal>.</para>
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</refsection>
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@ -201,6 +220,6 @@ $ ./pan/gui/pan
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</variablelist>
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</refsection>
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</refentry>
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@ -106,7 +106,7 @@ the single Nix expression in that directory
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here, the entire remainder of the file is the body of the
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function; when given the required arguments, the body should
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describe how to build an instance of the Hello package.</para>
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</callout>
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<callout arearefs='ex-hello-nix-co-2'>
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@ -190,7 +190,7 @@ perl = perl;</programlisting>
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with the same name happen to be in scope.</para>
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</callout>
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</calloutlist>
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</para>
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@ -301,7 +301,7 @@ steps:</para>
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(<literal>make install</literal>).</para>
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</callout>
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</calloutlist>
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<para>If you are wondering about the absence of error checking on the
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@ -321,7 +321,7 @@ error check.</para>
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...
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rec { <co xml:id='ex-hello-composition-co-1' />
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hello = import ../applications/misc/hello/ex-1 <co xml:id='ex-hello-composition-co-2' /> { <co xml:id='ex-hello-composition-co-3' />
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inherit fetchurl stdenv perl;
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};
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@ -330,10 +330,10 @@ rec { <co xml:id='ex-hello-composition-co-1' />
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inherit fetchurl stdenv;
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};
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fetchurl = import ../build-support/fetchurl {
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fetchurl = import ../build-support/fetchurl {
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inherit stdenv; ...
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};
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stdenv = ...;
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}
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@ -476,8 +476,8 @@ that the path denoted by <envar>out</envar> is now
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will see that the path is already valid and finish immediately. If a
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build fails, either because it returns a non-zero exit code, because
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Nix or the builder are killed, or because the machine crashes, then
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the output path will not be registered as valid. If you try to build
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the derivation again, Nix will remove the output path if it exists
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the output paths will not be registered as valid. If you try to build
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the derivation again, Nix will remove the output paths if they exist
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(e.g., because the builder died half-way through <literal>make
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install</literal>) and try again. Note that there is no
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<quote>negative caching</quote>: Nix doesn't remember that a build
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@ -543,7 +543,7 @@ genericBuild <co xml:id='ex-hello-builder2-co-3' /></programlisting>
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<calloutlist>
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<callout arearefs='ex-hello-builder2-co-1'>
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<para>The <envar>buildInputs</envar> variable tells
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<filename>setup</filename> to use the indicated packages as
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<quote>inputs</quote>. This means that if a package provides a
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@ -568,7 +568,7 @@ genericBuild <co xml:id='ex-hello-builder2-co-3' /></programlisting>
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the file <literal>$stdenv/setup</literal>.</para>
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</callout>
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<callout arearefs='ex-hello-builder2-co-3'>
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<para>The final step calls the shell function
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@ -580,7 +580,7 @@ genericBuild <co xml:id='ex-hello-builder2-co-3' /></programlisting>
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see <xref linkend='sec-standard-environment' />.</para>
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</callout>
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</calloutlist>
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<para>Discerning readers will note that the
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@ -704,7 +704,7 @@ configureFlags = "
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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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<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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@ -726,7 +726,7 @@ configureFlags = "
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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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@ -745,7 +745,7 @@ stdenv.mkDerivation {
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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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}
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</programlisting>
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</para>
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@ -781,7 +781,7 @@ stdenv.mkDerivation {
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<listitem><para><emphasis>Booleans</emphasis> with values
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<literal>true</literal> and
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<literal>false</literal>.</para></listitem>
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</itemizedlist>
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</para>
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@ -931,7 +931,7 @@ propagate attributes). This can be shortened using the
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<literal>inherit</literal> keyword. For instance,
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<programlisting>
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let x = 123; in
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let x = 123; in
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{ inherit x;
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y = 456;
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}</programlisting>
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@ -982,7 +982,7 @@ argument. There are three kinds of patterns:</para>
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<itemizedlist>
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<listitem><para>If a pattern is a single identifier, then the
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function matches any argument. Example:
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@ -1002,7 +1002,7 @@ map (concat "foo") [ "bar" "bla" "abc" ]</programlisting>
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evaluates to <literal>[ "foobar" "foobla"
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"fooabc" ]</literal>.</para></listitem>
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<listitem><para>An <emphasis>attribute set pattern</emphasis> of the
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form <literal>{ name1, name2, …, nameN }</literal>
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matches an attribute set containing the listed attributes, and binds
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@ -1016,7 +1016,7 @@ map (concat "foo") [ "bar" "bla" "abc" ]</programlisting>
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<varname>x</varname>, <varname>y</varname> and
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<varname>z</varname>. No other attributes are allowed. If you want
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to allow additional arguments, you can use an ellipsis
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(<literal>...</literal>):
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(<literal>...</literal>):
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<programlisting>
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{ x, y, z, ... }: z + y + x</programlisting>
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@ -1164,7 +1164,7 @@ used in the Nix expression for Subversion.</para>
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</calloutlist>
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</simplesect>
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<simplesect><title>With-expressions</title>
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@ -1343,7 +1343,7 @@ set, the attributes of which specify the inputs of the build.</para>
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<listitem><para>There must be an attribute named
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<varname>name</varname> whose value must be a string. This is used
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as a symbolic name for the package by <command>nix-env</command>,
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and it is appended to the hash in the output path of the
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and it is appended to the output paths of the
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derivation.</para></listitem>
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<listitem><para>There must be an attribute named
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@ -1358,7 +1358,7 @@ set, the attributes of which specify the inputs of the build.</para>
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<itemizedlist>
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<listitem><para>Strings, URIs, and integers are just passed
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<listitem><para>Strings and integers are just passed
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verbatim.</para></listitem>
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<listitem><para>A <emphasis>path</emphasis> (e.g.,
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@ -1369,8 +1369,8 @@ set, the attributes of which specify the inputs of the build.</para>
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should reside in the Nix store.</para></listitem>
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<listitem><para>A <emphasis>derivation</emphasis> causes that
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derivation to be built prior to the present derivation; the
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output path is put in the environment
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derivation to be built prior to the present derivation; its
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default output path is put in the environment
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variable.</para></listitem>
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<listitem><para>Lists of the previous types are also allowed.
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@ -1389,14 +1389,48 @@ set, the attributes of which specify the inputs of the build.</para>
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specifies command-line arguments to be passed to the builder. It
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should be a list.</para></listitem>
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<listitem><para>The optional attribute <varname>outputs</varname>
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specifies a list of symbolic outputs of the derivation. By default,
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a derivation produces a single output path, denoted as
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<literal>out</literal>. However, derivations can produce multiple
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output paths. This is useful because it allows outputs to be
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downloaded or garbage-collected separately. For instance, imagine a
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library package that provides a dynamic library, header files, and
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documentation. A program that links against the library doesn’t
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need the header files and documentation at runtime, and it doesn’t
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need the documentation at build time. Thus, the library package
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could specify:
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<programlisting>
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outputs = [ "lib" "headers" "doc" ];
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</programlisting>
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This will cause Nix to pass environment variables
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<literal>lib</literal>, <literal>headers</literal> and
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<literal>doc</literal> to the builder containing the intended store
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paths of each output. The builder would typically do something like
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<programlisting>
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./configure --libdir=$lib/lib --includedir=$headers/include --docdir=$doc/share/doc
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</programlisting>
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for an Autoconf-style package. You can refer to each output of a
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derivation by selecting it as an attribute, e.g.
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<programlisting>
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buildInputs = [ pkg.lib pkg.headers ];
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</programlisting>
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The first element of <varname>output</varname> determines the
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<emphasis>default output</emphasis>. Thus, you could also write
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<programlisting>
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buildInputs = [ pkg pkg.headers ];
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</programlisting>
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since <literal>pkg</literal> is equivalent to
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<literal>pkg.lib</literal>.</para></listitem>
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</itemizedlist>
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<para>(Note that <function>mkDerivation</function> in the standard
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<para>The function <function>mkDerivation</function> in the standard
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environment is a wrapper around <function>derivation</function> that
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adds a default value for <varname>system</varname> and always uses
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Bash as the builder, to which the supplied builder is passed as a
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command-line argument. See <xref linkend='sec-standard-environment'
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/>.)</para>
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/>.</para>
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<para>The builder is executed as follows:
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@ -1440,17 +1474,19 @@ command-line argument. See <xref linkend='sec-standard-environment'
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top-level Nix store directory (typically,
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<filename>/nix/store</filename>).</para></listitem>
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<listitem><para><envar>out</envar> is set to point to the output
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path of the derivation, which is a subdirectory of the Nix store.
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The output path is a concatenation of the cryptographic hash of
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all build inputs, and the <varname>name</varname>
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attribute.</para></listitem>
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<listitem><para>For each output declared in
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<varname>outputs</varname>, the corresponding environment variable
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is set to point to the intended path in the Nix store for that
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output. Each output path is a concatenation of the cryptographic
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hash of all build inputs, the <varname>name</varname> attribute
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and the output name. (The output name is omitted if it’s
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<literal>out</literal>.)</para></listitem>
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</itemizedlist>
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</para></listitem>
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<listitem><para>If the output path already exists, it is removed.
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<listitem><para>If an output path already exists, it is removed.
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Also, locks are acquired to prevent multiple Nix instances from
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performing the same build at the same time.</para></listitem>
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@ -1464,14 +1500,11 @@ command-line argument. See <xref linkend='sec-standard-environment'
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<listitem><para>The temporary directory is removed (unless the
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<option>-K</option> option was specified).</para></listitem>
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<listitem><para>If the build was successful, Nix scans the output
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for references to the paths of the inputs. These so-called
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<emphasis>retained dependencies</emphasis> could be used when the
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output of the derivation is used (e.g., when it's executed or used
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as input to another derivation), so if we deploy the derivation, we
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should copy the retained dependencies as well. The scan is
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performed by looking for the hash parts of file names of the
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inputs.</para></listitem>
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<listitem><para>If the build was successful, Nix scans each output
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path for references to input paths by looking for the hash parts of
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the input paths. Since these are potential runtime dependencies,
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Nix registers them as dependencies of the output
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paths.</para></listitem>
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<listitem><para>After the build, Nix sets the last-modified
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timestamp on all files in the build result to 1 (00:00:01 1/1/1970
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@ -1497,7 +1530,7 @@ attributes.</para>
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<variablelist>
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<varlistentry><term><varname>allowedReferences</varname></term>
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<listitem><para>The optional attribute
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<varname>allowedReferences</varname> specifies a list of legal
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references (dependencies) of the output of the builder. For
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@ -1515,7 +1548,7 @@ allowedReferences = [];
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</varlistentry>
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<varlistentry><term><varname>exportReferencesGraph</varname></term>
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<listitem><para>This attribute allows builders access to the
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@ -1626,7 +1659,7 @@ stdenv.mkDerivation {
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outputHashMode = "flat";
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outputHashAlgo = "md5";
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outputHash = md5;
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inherit url;
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}
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</programlisting>
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@ -1655,7 +1688,7 @@ stdenv.mkDerivation {
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<para>This is the default.</para></listitem>
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</varlistentry>
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<varlistentry><term><literal>"recursive"</literal></term>
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<listitem><para>The hash is computed over the NAR archive dump
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@ -1676,10 +1709,10 @@ stdenv.mkDerivation {
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linkend="sec-nix-hash"><command>nix-hash</command> command</link>
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for information about converting to and from base-32
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notation.)</para></listitem>
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</varlistentry>
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<varlistentry><term><varname>impureEnvVars</varname></term>
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<listitem><para>This attribute allows you to specify a list of
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@ -1706,7 +1739,7 @@ impureEnvVars = [ "http_proxy" "https_proxy" <replaceable>...</replaceable> ];
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</varlistentry>
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<varlistentry><term><varname>preferLocalBuild</varname></term>
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<listitem><para>If this attribute is set to
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