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* Manual updates.

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Eelco Dolstra 2003-11-27 14:58:32 +00:00
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4
doc/manual/Makefile.am
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@ -1,7 +1,9 @@
ENV = SGML_CATALOG_FILES=$(docbookcatalog)
XMLLINT = $(ENV) $(xmllint) $(xmlflags) --catalogs
XSLTPROC = $(ENV) $(xsltproc) $(xmlflags) --catalogs
XSLTPROC = $(ENV) $(xsltproc) $(xmlflags) --catalogs \
--param section.autolabel 1 \
--param section.label.includes.component.label 1
SOURCES = book.xml introduction.xml installation.xml \
overview.xml \

2
doc/manual/installation.xml
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@ -117,7 +117,7 @@ $ autoreconf -i</screen>
<para>
To use Nix, some environment variables should be set. In particular,
<literal>PATH</literal> should contain the directories
<envar>PATH</envar> should contain the directories
<filename><replaceable>prefix</replaceable>/bin</filename> and
<filename><replaceable>prefix</replaceable>/var/nix/links/current/bin</filename>.
The first directory contains the Nix tools themselves, while the second

177
doc/manual/overview.xml
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@ -14,10 +14,9 @@
installed or available for installation, and so on. These are operations
on the <emphasis>user environment</emphasis>: the set of packages that a
user <quote>sees</quote>. In a command line Unix environment, this means
the set of programs that are available through the
<literal>PATH</literal> environment variable. (In other environments it
might mean the set of programs available on the desktop, through the
start menu, and so on.)
the set of programs that are available through the <envar>PATH</envar>
environment variable. (In other environments it might mean the set of
programs available on the desktop, through the start menu, and so on.)
</para>
<para>
@ -183,8 +182,8 @@ obtaining list of Nix archives at http://losser.st-lab.cs.uu.nl/~eelco/nix-dist.
<para>
Assuming that the <literal>pan</literal> installation produced no errors,
it can be used immediately, that is, it now appears in a directory in the
<literal>PATH</literal> environment variable. Specifically,
<literal>PATH</literal> includes the entry
<envar>PATH</envar> environment variable. Specifically,
<envar>PATH</envar> includes the entry
<filename><replaceable>prefix</replaceable>/var/nix/links/current/bin</filename>,
where
<filename><replaceable>prefix</replaceable>/var/nix/links/current</filename>
@ -239,6 +238,172 @@ $ nix-env -u pan-0.14.2</screen>
</sect1>
<sect1>
<title>Writing Nix expressions</title>
<sect2>
<title>A simple Nix expression</title>
<para>
This section shows how to write simple Nix expressions&mdash;the things
that describe how to build a package.
</para>
<example id='ex-hello-nix'>
<title>Nix expression for GNU Hello</title>
<programlisting>
{stdenv, fetchurl, perl}: <co id='ex-hello-nix-co-1' />
derivation { <co id='ex-hello-nix-co-2' />
name = "hello-2.1.1"; <co id='ex-hello-nix-co-3' />
system = stdenv.system; <co id='ex-hello-nix-co-4' />
builder = ./builder.sh; <co id='ex-hello-nix-co-5' />
src = fetchurl { <co id='ex-hello-nix-co-6' />
url = ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz;
md5 = "70c9ccf9fac07f762c24f2df2290784d";
};
stdenv = stdenv; <co id='ex-hello-nix-co-7' />
perl = perl;
}
</programlisting>
</example>
<para>
A simple Nix expression is shown in <xref linkend='ex-hello-nix' />. It
describes how to the build the <ulink
url='http://www.gnu.org/directory/GNU/hello.html'>GNU Hello
package</ulink>. This package has several dependencies. First, it
requires a number of other packages, such as a C compiler, standard
Unix shell tools, and Perl. Rather than have this Nix expression refer
to and use specific versions of these packages, it should be generic;
that is, it should be a <emphasis>function</emphasis> that takes the
required packages as inputs and yield a build of the GNU Hello package
as a result. This Nix expression defines a function with three
arguments <xref linkend='ex-hello-nix-co-1' />, namely:
<orderedlist>
<listitem><para><varname>stdenv</varname>, which should be a
<emphasis>standard environment package</emphasis>. The standard
environment is a set of tools and other components that would be
expected in a fairly minimal Unix-like environment: a C compiler
and linker, Unix shell tools, and so on.</para>
</listitem>
<listitem><para><varname>fetchurl</varname>, which should be a
function that given parameters <varname>url</varname> and
<varname>md5</varname>, will fetch a file from the specified
location and check that this file has the given MD5 hash code.
The hash is required because build operations must be
<emphasis>pure</emphasis>: given the same inputs they should
always yield the same output. Since network resources can change
at any time, we must in some way guarantee what the result will
be.</para>
</listitem>
<listitem><para><varname>perl</varname>, which should be a Perl
interpreter.</para>
</listitem>
</orderedlist>
</para>
<para>
The remainder of the file is the body of the function, which happens to
be a <emphasis>derivation</emphasis> <xref
linkend='ex-hello-nix-co-2' />, which is the built-in function
<varname>derivation</varname> applied to a set of attributes that
encode all the necessary information for building the GNU Hello
package.
</para>
<example>
<title>Build script (<filename>builder.sh</filename>) for GNU
Hello</title>
<programlisting>
#! /bin/sh
buildinputs="$perl"
. $stdenv/setup || exit 1
tar xvfz $src || exit 1
cd hello-* || exit 1
./configure --prefix=$out || exit 1
make || exit 1
make install || exit 1
</programlisting>
</example>
</sect2>
<sect2>
<title>A more complex Nix expression</title>
<example id='ex-svn-nix'>
<title>Nix expression for Subversion</title>
<programlisting>
{ localServer ? false <co id='ex-svn-nix-co-1' />
, httpServer ? false
, sslSupport ? false
, swigBindings ? false
, stdenv, fetchurl
, openssl ? null, httpd ? null, db4 ? null, expat, swig ? null
}:
assert !isNull expat; <co id='ex-svn-nix-co-2' />
assert localServer -> !isNull db4;
assert httpServer -> !isNull httpd &amp;&amp; httpd.expat == expat; <co id='ex-svn-nix-co-3' />
assert sslSupport -> !isNull openssl &amp;&amp; (httpServer -> httpd.openssl == openssl);
assert swigBindings -> !isNull swig;
derivation {
name = "subversion-0.32.1";
system = stdenv.system;
builder = ./builder.sh;
src = fetchurl {
url = http://svn.collab.net/tarballs/subversion-0.32.1.tar.gz;
md5 = "b06717a8ef50db4b5c4d380af00bd901";
};
localServer = localServer;
httpServer = httpServer;
sslSupport = sslSupport;
swigBindings = swigBindings;
stdenv = stdenv;
openssl = if sslSupport then openssl else null; <co id='ex-svn-nix-co-4' />
httpd = if httpServer then httpd else null;
expat = expat;
db4 = if localServer then db4 else null;
swig = if swigBindings then swig else null;
}
</programlisting>
</example>
<para>
This example shows several features. Default parameters <xref
linkend='ex-svn-nix-co-1'/> can be used to simplify call sites: if an
argument that has a default is omitted, its default value is used.
</para>
<para>
You can use <emphasis>assertions</emphasis> to test whether arguments
satisfy certain constraints. The simple assertion <xref
linkend='ex-svn-nix-co-2'/> tests whether the
<varname>expat</varname> argument is not a null value. The more
complex assertion <xref linkend='ex-svn-nix-co-3'/> says that if
Subversion is built with Apache support, then <varname>httpd</varname>
(the Apache package) must not be null and it must have been built using
the same instance of the <varname>expat</varname> library as was passed
to the Subversion expression. This is since the Subversion code is
dynamically linked against the Apache code and they both use Expat,
they must be linked against the same instance&mdash;otherwise a
conflict might occur.
</para>
</sect2>
</sect1>
</chapter>
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