* Documented the `--query' operation.
This commit is contained in:
Eelco Dolstra
parent
b4f88d0ec3
commit
c34a153ae5
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@ -15,6 +15,23 @@
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</para>
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</para>
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</listitem>
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</listitem>
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<listitem>
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<para>
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Unify the concepts of successors and substitutes into a general notion
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of <emphasis>equivalent expressions</emphasis>. Expressions are
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equivalent if they have the same target paths with the same
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identifiers. However, even though they are functionally equivalent,
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they may differ stronly with respect to their <emphasis>performance
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characteristics</emphasis>. For example, realising a slice is more
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efficient that realising the derivation from which that slice was
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produced. On the other hand, distributing sources may be more
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efficient (storage- or bandwidth-wise) than distributing binaries. So
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we need to be able to attach weigths or priorities or performance
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annotations to expressions; Nix can then choose the most efficient
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expression dependent on the context.
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</para>
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</listitem>
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</itemizedlist>
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</itemizedlist>
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</appendix>
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</appendix>
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@ -126,6 +126,8 @@
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</refsect1>
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</refsect1>
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<!--######################################################################-->
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<refsect1>
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<refsect1>
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<title>Operation <option>--install</option></title>
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<title>Operation <option>--install</option></title>
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@ -162,6 +164,8 @@
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</refsect1>
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</refsect1>
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<!--######################################################################-->
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<refsect1>
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<refsect1>
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<title>Operation <option>--delete</option></title>
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<title>Operation <option>--delete</option></title>
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@ -203,6 +207,216 @@
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</refsect1>
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</refsect1>
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<!--######################################################################-->
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<refsect1>
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<title>Operation <option>--query</option></title>
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<refsect2>
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<title>Synopsis</title>
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<cmdsynopsis>
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<command>nix</command>
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<group>
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<arg><option>--query</option></arg>
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<arg><option>-q</option></arg>
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</group>
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<group>
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<group>
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<arg><option>--list</option></arg>
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<arg><option>-l</option></arg>
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</group>
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<group>
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<arg><option>--requisites</option></arg>
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<arg><option>-r</option></arg>
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</group>
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<group>
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<arg><option>--expansion</option></arg>
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<arg><option>-e</option></arg>
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</group>
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<group>
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<arg><option>--graph</option></arg>
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<arg><option>-g</option></arg>
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</group>
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</group>
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<arg choice='plain' rep='repeat'><replaceable>args</replaceable></arg>
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</cmdsynopsis>
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</refsect2>
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<refsect2>
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<title>Description</title>
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<para>
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The operation <option>--query</option> displays various bits of
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information about Nix expressions or paths in the store. The queries
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are described in <xref linkend='nixref-queries' />. At most one query
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can be specified; the default query is <option>--list</option>.
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</para>
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</refsect2>
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<refsect2 id='nixref-queries'>
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<title>Queries</title>
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<variablelist>
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<varlistentry>
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<term><option>--list</option></term>
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<listitem>
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<para>
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Prints out the target paths of the Nix expressions indicated by
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the identifiers <replaceable>args</replaceable>. In the case of
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a derivation expression, these are the paths that will be
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produced by the builder of the expression. In the case of a
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slice expression, these are the root paths (which are generally
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the paths that were produced by the builder of the derivation
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expression of which the slice is a normal form).
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</para>
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<para>
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This query has one option:
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</para>
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<variablelist>
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<varlistentry>
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<term><option>--normalise</option></term>
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<listitem>
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<para>
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Causes the target paths of the <emphasis>normal
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forms</emphasis> of the expressions to be printed, rather
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than the target paths of the expressions themselves.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--requisites</option></term>
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<listitem>
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<para>
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Prints out the requisite paths of the Nix expressions indicated
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by the identifiers <replaceable>args</replaceable>. The
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requisite paths of a Nix expression are the paths that need to be
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present in the system to be able to realise the expression. That
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is, they form the <emphasis>closure</emphasis> of the expression
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in the file system (i.e., no path in the set of requisite paths
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points to anything outside the set of requisite paths).
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</para>
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<para>
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The notion of requisite paths is very useful when one wants to
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distribute Nix expressions. Since they form a closure, they are
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the only paths one needs to distribute to another system to be
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able to realise the expression on the other system.
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</para>
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<para>
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This query is generally used to implement various kinds of
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distribution. A <emphasis>source distribution</emphasis> is
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obtained by distributing the requisite paths of a derivation
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expression. A <emphasis>binary distribution</emphasis> is
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obtained by distributing the requisite paths of a slice
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expression (i.e., the normal form of a derivation expression; you
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can directly specify the identifier of the slice expression, or
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use <option>--normalise</option> and specify the identifier of a
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derivation expression). A <emphasis>cache
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distribution</emphasis> is obtained by distributing the
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requisite paths of a derivation expression and specifying the
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option <option>--include-successors</option>. This will include
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not just the paths of a source and binary distribution, but also
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all expressions and paths of subterms of the source. This is
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useful if one wants to realise on the target system a Nix
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expression that is similar but not quite the same as the one
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being distributed, since any common subterms will be reused.
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</para>
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<para>
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This query has a number of options:
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</para>
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<variablelist>
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<varlistentry>
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<term><option>--normalise</option></term>
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<listitem>
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<para>
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Causes the requisite paths of the <emphasis>normal
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forms</emphasis> of the expressions to be printed, rather
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than the requisite paths of the expressions themselves.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--exclude-exprs</option></term>
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<listitem>
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<para>
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Excludes the paths of Nix expressions. This causes the
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closure property to be lost, that is, the resulting set of
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paths is not enough to ensure realisibility.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--include-successors</option></term>
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<listitem>
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<para>
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Also include the requisites of successors (normal forms).
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Only the requisites of <emphasis>known</emphasis>
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successors are included, i.e., the normal forms of
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derivation expressions that have never been normalised will
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not be included.
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</para>
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<para>
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Note that not just the successor of a derivation expression
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will be included, but also the successors of all input
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expressions of that derivation expression. I.e., all
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normal forms of subterms involved in the normalisation of
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the top-level term are included.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--expansion</option></term>
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<listitem>
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<para>
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For each identifier in <replaceable>args</replaceable>, prints
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all expansions of that identifier, that is, all paths whose
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current content matches the identifier.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--graph</option></term>
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<listitem>
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<para>
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Prints a graph of the closure of the expressions identified by
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<replaceable>args</replaceable> in the format of the
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<command>dot</command> tool of AT&T's GraphViz package.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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</refentry>
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</refentry>
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@ -35,8 +35,7 @@
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</para>
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</para>
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<screen>
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<screen>
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$ rm `db_archive -a -h
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$ rm `db_archive -a -h <replaceable>prefix</replaceable>/var/nix/db`</screen>
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<replaceable>prefix</replaceable>/var/nix/db`</screen>
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</sect1>
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</sect1>
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