forked from lix-project/lix
Remove unused file
This commit is contained in:
Eelco Dolstra
parent
a7b8f79938
commit
26fcab53e0
|
|
@ -1,119 +0,0 @@
|
||||||
<section xmlns="http://docbook.org/ns/docbook"
|
|
||||||
xmlns:xlink="http://www.w3.org/1999/xlink"
|
|
||||||
xmlns:xi="http://www.w3.org/2001/XInclude"
|
|
||||||
version="5.0"
|
|
||||||
xml:id='sec-builder-syntax'>
|
|
||||||
|
|
||||||
<title>Builder Syntax</title>
|
|
||||||
|
|
||||||
<example xml:id='ex-hello-builder'><title>Build script for GNU Hello
|
|
||||||
(<filename>builder.sh</filename>)</title>
|
|
||||||
<programlisting>
|
|
||||||
source $stdenv/setup <co xml:id='ex-hello-builder-co-1' />
|
|
||||||
|
|
||||||
PATH=$perl/bin:$PATH <co xml:id='ex-hello-builder-co-2' />
|
|
||||||
|
|
||||||
tar xvfz $src <co xml:id='ex-hello-builder-co-3' />
|
|
||||||
cd hello-*
|
|
||||||
./configure --prefix=$out <co xml:id='ex-hello-builder-co-4' />
|
|
||||||
make <co xml:id='ex-hello-builder-co-5' />
|
|
||||||
make install</programlisting>
|
|
||||||
</example>
|
|
||||||
|
|
||||||
<para><xref linkend='ex-hello-builder' /> shows the builder referenced
|
|
||||||
from Hello's Nix expression (stored in
|
|
||||||
<filename>pkgs/applications/misc/hello/ex-1/builder.sh</filename>).
|
|
||||||
The builder can actually be made a lot shorter by using the
|
|
||||||
<emphasis>generic builder</emphasis> functions provided by
|
|
||||||
<varname>stdenv</varname>, but here we write out the build steps to
|
|
||||||
elucidate what a builder does. It performs the following
|
|
||||||
steps:</para>
|
|
||||||
|
|
||||||
<calloutlist>
|
|
||||||
|
|
||||||
<callout arearefs='ex-hello-builder-co-1'>
|
|
||||||
|
|
||||||
<para>When Nix runs a builder, it initially completely clears the
|
|
||||||
environment (except for the attributes declared in the
|
|
||||||
derivation). For instance, the <envar>PATH</envar> variable is
|
|
||||||
empty<footnote><para>Actually, it's initialised to
|
|
||||||
<filename>/path-not-set</filename> to prevent Bash from setting it
|
|
||||||
to a default value.</para></footnote>. This is done to prevent
|
|
||||||
undeclared inputs from being used in the build process. If for
|
|
||||||
example the <envar>PATH</envar> contained
|
|
||||||
<filename>/usr/bin</filename>, then you might accidentally use
|
|
||||||
<filename>/usr/bin/gcc</filename>.</para>
|
|
||||||
|
|
||||||
<para>So the first step is to set up the environment. This is
|
|
||||||
done by calling the <filename>setup</filename> script of the
|
|
||||||
standard environment. The environment variable
|
|
||||||
<envar>stdenv</envar> points to the location of the standard
|
|
||||||
environment being used. (It wasn't specified explicitly as an
|
|
||||||
attribute in <xref linkend='ex-hello-nix' />, but
|
|
||||||
<varname>mkDerivation</varname> adds it automatically.)</para>
|
|
||||||
|
|
||||||
</callout>
|
|
||||||
|
|
||||||
<callout arearefs='ex-hello-builder-co-2'>
|
|
||||||
|
|
||||||
<para>Since Hello needs Perl, we have to make sure that Perl is in
|
|
||||||
the <envar>PATH</envar>. The <envar>perl</envar> environment
|
|
||||||
variable points to the location of the Perl package (since it
|
|
||||||
was passed in as an attribute to the derivation), so
|
|
||||||
<filename><replaceable>$perl</replaceable>/bin</filename> is the
|
|
||||||
directory containing the Perl interpreter.</para>
|
|
||||||
|
|
||||||
</callout>
|
|
||||||
|
|
||||||
<callout arearefs='ex-hello-builder-co-3'>
|
|
||||||
|
|
||||||
<para>Now we have to unpack the sources. The
|
|
||||||
<varname>src</varname> attribute was bound to the result of
|
|
||||||
fetching the Hello source tarball from the network, so the
|
|
||||||
<envar>src</envar> environment variable points to the location in
|
|
||||||
the Nix store to which the tarball was downloaded. After
|
|
||||||
unpacking, we <command>cd</command> to the resulting source
|
|
||||||
directory.</para>
|
|
||||||
|
|
||||||
<para>The whole build is performed in a temporary directory
|
|
||||||
created in <varname>/tmp</varname>, by the way. This directory is
|
|
||||||
removed after the builder finishes, so there is no need to clean
|
|
||||||
up the sources afterwards. Also, the temporary directory is
|
|
||||||
always newly created, so you don't have to worry about files from
|
|
||||||
previous builds interfering with the current build.</para>
|
|
||||||
|
|
||||||
</callout>
|
|
||||||
|
|
||||||
<callout arearefs='ex-hello-builder-co-4'>
|
|
||||||
|
|
||||||
<para>GNU Hello is a typical Autoconf-based package, so we first
|
|
||||||
have to run its <filename>configure</filename> script. In Nix
|
|
||||||
every package is stored in a separate location in the Nix store,
|
|
||||||
for instance
|
|
||||||
<filename>/nix/store/9a54ba97fb71b65fda531012d0443ce2-hello-2.1.1</filename>.
|
|
||||||
Nix computes this path by cryptographically hashing all attributes
|
|
||||||
of the derivation. The path is passed to the builder through the
|
|
||||||
<envar>out</envar> environment variable. So here we give
|
|
||||||
<filename>configure</filename> the parameter
|
|
||||||
<literal>--prefix=$out</literal> to cause Hello to be installed in
|
|
||||||
the expected location.</para>
|
|
||||||
|
|
||||||
</callout>
|
|
||||||
|
|
||||||
<callout arearefs='ex-hello-builder-co-5'>
|
|
||||||
|
|
||||||
<para>Finally we build Hello (<literal>make</literal>) and install
|
|
||||||
it into the location specified by <envar>out</envar>
|
|
||||||
(<literal>make install</literal>).</para>
|
|
||||||
|
|
||||||
</callout>
|
|
||||||
|
|
||||||
</calloutlist>
|
|
||||||
|
|
||||||
<para>If you are wondering about the absence of error checking on the
|
|
||||||
result of various commands called in the builder: this is because the
|
|
||||||
shell script is evaluated with Bash's <option>-e</option> option,
|
|
||||||
which causes the script to be aborted if any command fails without an
|
|
||||||
error check.</para>
|
|
||||||
|
|
||||||
</section>
|
|
||||||
Loading…
Reference in a new issue