diff options
Diffstat (limited to 'doc/manual/writing-nix-expressions.xml')
| -rw-r--r-- | doc/manual/writing-nix-expressions.xml | 63 |
1 files changed, 30 insertions, 33 deletions
diff --git a/doc/manual/writing-nix-expressions.xml b/doc/manual/writing-nix-expressions.xml index d29f76f19a..dae7d9073b 100644 --- a/doc/manual/writing-nix-expressions.xml +++ b/doc/manual/writing-nix-expressions.xml @@ -83,9 +83,7 @@ the single Nix expression in that directory would expect in a basic Unix environment: a C/C++ compiler (GCC, to be precise), the Bash shell, fundamental Unix tools such as <command>cp</command>, <command>grep</command>, - <command>tar</command>, etc. (See - <filename>pkgs/stdenv/nix/path.nix</filename> to see what's in - <command>stdenv</command>.) <varname>fetchurl</varname> is a + <command>tar</command>, etc. <varname>fetchurl</varname> is a function that downloads files. <varname>perl</varname> is the Perl interpreter.</para> @@ -109,12 +107,12 @@ the single Nix expression in that directory <varname>mkDerivation</varname> is a function provided by <varname>stdenv</varname> that builds a component from a set of <emphasis>attributes</emphasis>. An attribute set is just a list - of key/value pairs where the value is an arbitrary Nix expression. - They take the general form + of key/value pairs where each value is an arbitrary Nix + expression. They take the general form <literal>{<replaceable>name1</replaceable> = <replaceable>expr1</replaceable>; <replaceable>...</replaceable> - <replaceable>name1</replaceable> = - <replaceable>expr1</replaceable>;</literal>.</para> + <replaceable>nameN</replaceable> = + <replaceable>exprN</replaceable>;}</literal>.</para> </callout> @@ -148,11 +146,11 @@ the single Nix expression in that directory <para>The builder has to know what the sources of the component are. Here, the attribute <varname>src</varname> is bound to the result of a call to the <command>fetchurl</command> function. - Given a URL and a MD5 hash of the expected contents of the file at - that URL, this function actually builds a derivation that - downloads the file and checks its hash. So the sources are a - dependency that like all other dependencies is built before Hello - itself is built.</para> + Given a URL and an MD5 hash of the expected contents of the file + at that URL, this function builds a derivation that downloads the + file and checks its hash. So the sources are a dependency that + like all other dependencies is built before Hello itself is + built.</para> <para>Instead of <varname>src</varname> any other name could have been used, and in fact there can be any number of sources (bound @@ -172,7 +170,7 @@ the single Nix expression in that directory <programlisting> perl = perl;</programlisting> - will do the trink: it binds an attribute <varname>perl</varname> + will do the trick: it binds an attribute <varname>perl</varname> to the function argument which also happens to be called <varname>perl</varname>. However, it looks a bit silly, so there is a shorter syntax. The <literal>inherit</literal> keyword @@ -218,7 +216,8 @@ steps:</para> <callout arearefs='ex-hello-builder-co-1'> <para>When Nix runs a builder, it initially completely clears the - environment. For instance, the <envar>PATH</envar> variable is + 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 @@ -596,13 +595,11 @@ language. Purity means that operations in the language don't have side-effects (for instance, there is no variable assignment). Laziness means that arguments to functions are evaluated only when they are needed. Functional means that functions are -<quote>normal</quote> values that can be passed around and -manipulated in interesting ways.</para> - -<para>The language is not a full-featured, general purpose language. -It's main job is to describe components, compositions of components, -and the variability within components. For this a functional language -is perfectly suited.</para> +<quote>normal</quote> values that can be passed around and manipulated +in interesting ways. The language is not a full-featured, general +purpose language. It's main job is to describe components, +compositions of components, and the variability within +components.</para> <para>This section presents the various features of the language.</para> @@ -773,7 +770,7 @@ and evaluates to <literal>"foobar"</literal>. <simplesect><title>Inheriting attributes</title> -<para>When defining an attribute set itt is often convenient to copy +<para>When defining an attribute set it is often convenient to copy variables from the surrounding lexical scope (e.g., when you want to propagate attributes). This can be shortened using the <literal>inherit</literal> keyword. For instance, @@ -849,7 +846,7 @@ let { </para> <para>It is also possible to define a function that takes a single -argument and that does need to be called with an attribute set as +argument and that does not need to be called with an attribute set as argument. The syntax is <programlisting> @@ -959,10 +956,10 @@ used in the Nix expression for Subversion.</para> <callout arearefs='ex-subversion-nix-co-2'> <para>This assertion says that in order for Subversion to have SSL support (so that it can access <literal>https</literal> URLs), an - OpenSSL library must be passed. Additionally, it says + OpenSSL library must be passed. Additionally, it says that <emphasis>if</emphasis> Apache support is enabled, then Apache's - OpenSSL should much Subversion's. (Note that if Apache support is - not enabled, we don't care about Apache's OpenSSL.)</para> + OpenSSL should match Subversion's. (Note that if Apache support + is not enabled, we don't care about Apache's OpenSSL.)</para> </callout> <callout arearefs='ex-subversion-nix-co-4'> @@ -1241,14 +1238,14 @@ command-line argument. See <xref linkend='sec-standard-environment' written to <filename>/nix/var/log/nix</filename>.</para></listitem> <listitem><para>The builder is executed with the arguments specified - by the attribute <varname>args</varname>. If it exit with exit code - 0, it is considered to have succeeded.</para></listitem> + by the attribute <varname>args</varname>. If it exits with exit + code 0, it is considered to have succeeded.</para></listitem> <listitem><para>The temporary directory is removed (unless the <option>-K</option> option was specified).</para></listitem> - <listitem><para>If the build was succesful, Nix scans the output for - references to the paths of the inputs. These so-called + <listitem><para>If the build was successful, Nix scans the output + for references to the paths of the inputs. These so-called <emphasis>retained dependencies</emphasis> could be used when the output of the derivation is used (e.g., when it's executed or used as input to another derivation), so if we deploy the derivation, we @@ -1406,7 +1403,7 @@ variable. The phases are: <listitem> - <para><function>unpackPhase</function>: unpacks the source files + <para><function>unpackPhase</function> unpacks the source files listed in the <envar>src</envar> environment variable to the current directory. It supports <filename>tar</filename> files, optionally compressed with <command>gzip</command> or @@ -1415,7 +1412,7 @@ variable. The phases are: environment; you should add it as a build input yourself); and unpacked source trees (i.e., directories; they are copied verbatim). You can add support for other file types by setting - the <varname>findUnpacker</varname> hook. This hook should set an + the <varname>findUnpacker</varname> hook. This hook should set the variable <varname>unpackCmd</varname> to contain the command to be executed to unpack the file.</para> @@ -1441,7 +1438,7 @@ variable. The phases are: <para><function>configurePhase</function> runs the script called <filename>configure</filename> in the current directory with a <option>--prefix</option> set to the output path. You can add - additional flag through the <varname>configureFlags</varname> + additional flags through the <varname>configureFlags</varname> variable. If <filename>configure</filename> does not exist, nothing happens.</para> |