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<!-- vim: set tw=120 ft=html sw=4 sts=4 et : -->

<h1>Hooks</h1>

<h2>Overview</h2>

<p>This document describes the Paludis hooks interface. A hook is a piece of code
that is executed when a particular well defined action occurs.</p>

<p>There are currently four categories of hooks:</p>

<ul>
    <li>General hooks. These have access to a limited environment. If
    a hook returns a non-zero exit code, the action will be aborted.
    See <a href="#general-hooks">General Hooks</a>.</li>

    <li>Ebuild phase hooks. These have <code>ebuild</code> in the hook name, and
    have full access to the ebuild environment (including the ability to call
    <code>die</code>), but are only used for ebuild-based activities.
    See <a href="#ebuild-phase-hooks">Ebuild Phase Hooks</a>.</li>

    <li>Ebuild message hooks. These are special hooks that are called for
    <code>einfo</code>, <code>ewarn</code> etc.
    See <a href="#ebuild-message-hooks">Ebuild Message Hooks</a>.</li>

    <li>Merger / Unmerger hooks. These are used when installing and uninstalling
    content to the live filesystem. If a check hook returns a non-zero exit
    code, the action will be aborted.
    See <a href="#merger-hooks">Merger / Unmerger Hooks</a>.</li>
</ul>

<p>There are currently five categories of hook execution code:</p>

<ul>
    <li><code>.bash</code> hooks. These are simple <code>.bash</code> files that
    are executed with a particular environment. See <a href="#bash-hooks">Bash Hooks</a>
    for details.</li>

    <li><code>.hook</code> hooks. These are also <code>bash</code> files, but rather
    than containing the relevant code in global scope, they make use of functions
    to perform hook actions. They also support specifying execution order dependencies
    upon other hooks. See <a href="#hook-hooks">Hook Hooks</a> for details.</li>

    <li><code>.py</code> hooks.  These are much like .hook hooks, but written in Python and
    with additional power given by Python bindings and access to the current Environment.
    See <a href="#py-hooks">Python Hooks</a> for details.</li>

    <li><code>.so</code> hooks.  These are written in C++ and compiled into shared
    libraries, and run inside the Paludis process. See <a href="#so-hooks">.so Hooks</a>
    for details.</li>

    <li>Repository hooks. These are implemented internally by <code>Repository</code>
    classes.</li>
</ul>

<p>Not all hook execution code methods are available for all hook categories. The
following table indicates availability:</p>

<table border="1" summary="Which methods are supported for which categories">
    <tr>
        <td></td>
        <th><code>.bash</code></th>
        <th><code>.hook</code></th>
        <th><code>.py</code></th>
        <th><code>.so</code></th>
        <th>Repository</th>
    </tr>
    <tr>
        <th>General</th>
        <td>yes</td>
        <td>yes</td>
        <td>yes</td>
        <td>yes</td>
        <td>yes</td>
    </tr>
    <tr>
        <th>Ebuild Phase</th>
        <td>yes</td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <th>Ebuild Message</th>
        <td>yes</td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <th>Merger</th>
        <td>yes</td>
        <td>yes</td>
        <td>yes</td>
        <td>yes</td>
        <td>yes</td>
    </tr>
</table>

<p>Where there is a choice, <code>.hook</code> hooks should be favoured over <code>.bash</code>
hooks.</p>

<h2>Available Hooks</h2>

<h3 id="general-hooks">General Hooks</h3>

<p>The following general normal hooks are available:</p>

<ul>
    <li><code>install_pre</code></li>
    <li><code>install_fail</code></li>
    <li><code>install_post</code></li>
    <li><code>install_all_pre</code></li>
    <li><code>install_all_post</code></li>
    <li><code>install_pretend_pre</code></li>
    <li><code>install_pretend_post</code></li>
    <li><code>install_pretend_display_item_pre</code></li>
    <li><code>install_pretend_display_item_post</code></li>
    <li><code>install_task_execute_pre</code></li>
    <li><code>install_task_execute_post</code></li>
    <li><code>uninstall_pre</code></li>
    <li><code>uninstall_fail</code></li>
    <li><code>uninstall_post</code></li>
    <li><code>uninstall_all_pre</code></li>
    <li><code>uninstall_all_post</code></li>
    <li><code>clean_pre</code></li>
    <li><code>clean_post</code></li>
    <li><code>clean_fail</code></li>
    <li><code>clean_all_pre</code></li>
    <li><code>clean_all_post</code></li>
    <li><code>sync_pre</code></li>
    <li><code>sync_fail</code></li>
    <li><code>sync_post</code></li>
    <li><code>sync_all_pre</code></li>
    <li><code>sync_all_post</code></li>
    <li><code>fetch_pre</code></li>
    <li><code>fetch_post</code></li>
    <li><code>fetch_all_pre</code></li>
    <li><code>fetch_all_post</code></li>
</ul>

<p>In general, certain special environment variables will be set:</p>

<ul>
    <li><code>HOOK</code> will contain the name of the hook.</li>
    <li>For <code>all</code> hooks, <code>TARGETS</code> will contain the targets
    for the operation.</li>
    <li>For non-<code>all</code> hooks, <code>TARGET</code> will contain the current
    target.</li>
    <li>The <code>PALUDIS_CMDLINE</code> variables described below are also available.
    <li>For the <code>install_pretend_display_item</code> hooks, the <code>KIND</code> variable will also be of
    interest.</li>
    <li>For the <code>install_task_execute_pre</code> and <code>install_task_execute_post</code> hooks,
    <code>PRETEND</code>, <code>FETCH_ONLY</code> and <code>SUCCESS</code> may be useful.</li>
</ul>

<h3 id="ebuild-phase-hooks">Ebuild Phase Hooks</h3>

<p>The following ebuild phase hooks are available:</p>

<ul>
    <li><code>ebuild_metadata_pre</code></li>
    <li><code>ebuild_metadata_fail</code></li>
    <li><code>ebuild_metadata_post</code></li>
    <li><code>ebuild_variable_pre</code></li>
    <li><code>ebuild_variable_fail</code></li>
    <li><code>ebuild_variable_post</code></li>
    <li><code>ebuild_init_pre</code></li>
    <li><code>ebuild_init_fail</code></li>
    <li><code>ebuild_init_post</code></li>
    <li><code>ebuild_initmisc_pre</code></li>
    <li><code>ebuild_initmisc_fail</code></li>
    <li><code>ebuild_initmisc_post</code></li>
    <li><code>ebuild_fetch_extra_pre</code></li>
    <li><code>ebuild_fetch_extra_fail</code></li>
    <li><code>ebuild_fetch_extra_post</code></li>
    <li><code>ebuild_tidyup_pre</code></li>
    <li><code>ebuild_tidyup_fail</code></li>
    <li><code>ebuild_tidyup_post</code></li>
    <li><code>ebuild_unpack_pre</code></li>
    <li><code>ebuild_unpack_fail</code></li>
    <li><code>ebuild_unpack_post</code></li>
    <li><code>ebuild_prepare_pre</code></li>
    <li><code>ebuild_prepare_fail</code></li>
    <li><code>ebuild_prepare_post</code></li>
    <li><code>ebuild_configure_pre</code></li>
    <li><code>ebuild_configure_fail</code></li>
    <li><code>ebuild_configure_post</code></li>
    <li><code>ebuild_compile_pre</code></li>
    <li><code>ebuild_compile_fail</code></li>
    <li><code>ebuild_compile_post</code></li>
    <li><code>ebuild_install_pre</code></li>
    <li><code>ebuild_install_fail</code></li>
    <li><code>ebuild_install_post</code></li>
    <li><code>ebuild_test_pre</code></li>
    <li><code>ebuild_test_fail</code></li>
    <li><code>ebuild_test_post</code></li>
    <li><code>ebuild_test_expensive_pre</code></li>
    <li><code>ebuild_test_expensive_fail</code></li>
    <li><code>ebuild_test_expensive_post</code></li>
    <li><code>ebuild_pretend_pre</code></li>
    <li><code>ebuild_pretend_fail</code></li>
    <li><code>ebuild_pretend_post</code></li>
    <li><code>ebuild_bad_options_pre</code></li>
    <li><code>ebuild_bad_options_fail</code></li>
    <li><code>ebuild_bad_options_post</code></li>
    <li><code>ebuild_bad_required_use_pre</code></li>
    <li><code>ebuild_bad_required_use_fail</code></li>
    <li><code>ebuild_bad_required_use_post</code></li>
    <li><code>ebuild_setup_pre</code></li>
    <li><code>ebuild_setup_fail</code></li>
    <li><code>ebuild_setup_post</code></li>
    <li><code>ebuild_config_pre</code></li>
    <li><code>ebuild_config_fail</code></li>
    <li><code>ebuild_config_post</code></li>
    <li><code>ebuild_nofetch_pre</code></li>
    <li><code>ebuild_nofetch_fail</code></li>
    <li><code>ebuild_nofetch_post</code></li>
    <li><code>ebuild_preinst_pre</code></li>
    <li><code>ebuild_preinst_fail</code></li>
    <li><code>ebuild_preinst_post</code></li>
    <li><code>ebuild_postinst_pre</code></li>
    <li><code>ebuild_postinst_fail</code></li>
    <li><code>ebuild_postinst_post</code></li>
    <li><code>ebuild_prerm_pre</code></li>
    <li><code>ebuild_prerm_fail</code></li>
    <li><code>ebuild_prerm_post</code></li>
    <li><code>ebuild_postrm_pre</code></li>
    <li><code>ebuild_postrm_fail</code></li>
    <li><code>ebuild_postrm_post</code></li>
    <li><code>ebuild_info_pre</code></li>
    <li><code>ebuild_info_fail</code></li>
    <li><code>ebuild_info_post</code></li>
    <li><code>ebuild_infovars_pre</code></li>
    <li><code>ebuild_infovars_fail</code></li>
    <li><code>ebuild_infovars_post</code></li>
    <li><code>ebuild_pivotbin_pre</code></li>
    <li><code>ebuild_pivotbin_fail</code></li>
    <li><code>ebuild_pivotbin_post</code></li>
    <li><code>ebuild_installbin_pre</code></li>
    <li><code>ebuild_installbin_fail</code></li>
    <li><code>ebuild_installbin_post</code></li>
    <li><code>ebuild_saveenv_pre</code></li>
    <li><code>ebuild_saveenv_fail</code></li>
    <li><code>ebuild_saveenv_post</code></li>
    <li><code>ebuild_loadenv_pre</code></li>
    <li><code>ebuild_loadenv_fail</code></li>
    <li><code>ebuild_loadenv_post</code></li>
    <li><code>ebuild_killold_pre</code></li>
    <li><code>ebuild_killold_fail</code></li>
    <li><code>ebuild_killold_post</code></li>
    <li><code>ebuild_tidyup_pre</code></li>
    <li><code>ebuild_tidyup_fail</code></li>
    <li><code>ebuild_tidyup_post</code></li>
</ul>

<p>These are called before and after the corresponding <code>src_</code>,
<code>pkg_</code> or <code>builtin_</code> phase functions (in particular,
note <code>src_configure</code> versus <code>pkg_config</code>).

<p>As well as the full ebuild environment, the <code>HOOK</code> environment
variable will contain the name of the hook being called. The
<code>PALUDIS_CMDLINE</code> variables described below are also available.</p>

<p>Ebuild hooks will <em>not</em> necessarily be called if an ebuild does not
define the function in question.</p>

<h3 id="ebuild-message-hooks">Ebuild Message Hooks</h3>

<p>The following ebuild message hooks are available:</p>

<ul>
    <li><code>einfo</code></li>
    <li><code>ewarn</code></li>
    <li><code>eerror</code></li>
    <li><code>elog</code></li>
</ul>

<p>The <code>HOOK</code> environment variable will contain the name of the hook
being called, and the <code>MESSAGE</code> environment variable will contain
the message being passed to the function.  The <code>PALUDIS_CMDLINE</code>
variables described below are also available.</p>

<h3 id="merger-hooks">Merger / Unmerger Hooks</h3>

<p>The merger runs in two stages, for safety. First it checks that it can
probably install safely, then it does the actual install. Note that calculating
the md5, timestamp etc for VDB CONTENTS is done <em>after</em> the install_post
hooks are called.</p>

<p>In each of the following subcategories, the hooks that do not name
a specific type of object are called before or after the entire
process; those that do are called once for each relevant item.</p>

<p>The following merger check hooks are available:</p>

<ul>
    <li><code>merger_check_pre</code></li>
    <li><code>merger_check_post</code></li>
    <li><code>merger_check_file_pre</code></li>
    <li><code>merger_check_file_post</code></li>
    <li><code>merger_check_sym_pre</code></li>
    <li><code>merger_check_sym_post</code></li>
    <li><code>merger_check_dir_pre</code></li>
    <li><code>merger_check_dir_post</code></li>
</ul>

<p>The <code>INSTALL_SOURCE</code> and <code>INSTALL_DESTINATION</code>
environment variables contain the target source and destination. The
<code>ROOT</code> variable contains the filesystem root. The <code>IMAGE</code>
variable contains the image root.</p>

<p>The following merger hooks are available:</p>

<ul>
    <li><code>merger_install_pre</code></li>
    <li><code>merger_install_post</code></li>
    <li><code>merger_install_file_pre</code></li>
    <li><code>merger_install_file_post</code></li>
    <li><code>merger_install_sym_pre</code></li>
    <li><code>merger_install_sym_post</code></li>
    <li><code>merger_install_dir_pre</code></li>
    <li><code>merger_install_dir_post</code></li>
    <li><code>merger_unlink_file_pre</code></li>
    <li><code>merger_unlink_file_post</code></li>
    <li><code>merger_unlink_dir_pre</code></li>
    <li><code>merger_unlink_dir_post</code></li>
    <li><code>merger_unlink_sym_pre</code></li>
    <li><code>merger_unlink_sym_post</code></li>
    <li><code>merger_unlink_misc_pre</code></li>
    <li><code>merger_unlink_misc_post</code></li>
</ul>

<p>Again, <code>ROOT</code> and <code>IMAGE</code> are available. For
install hooks, <code>INSTALL_SOURCE</code>, <code>INSTALL_DESTINATION</code> are
set, and for uninstall hooks, <code>UNLINK_TARGET</code>.</p>

<p>The unmerger hooks are used for uninstalling a package, but not when existing
things have to be removed for an install (the merger does that). The following
unmerger hooks are available:</p>

<ul>
    <li><code>unmerger_unlink_pre</code></li>
    <li><code>unmerger_unlink_post</code></li>
    <li><code>unmerger_unlink_file_pre</code></li>
    <li><code>unmerger_unlink_file_post</code></li>
    <li><code>unmerger_unlink_dir_pre</code></li>
    <li><code>unmerger_unlink_dir_post</code></li>
    <li><code>unmerger_unlink_sym_pre</code></li>
    <li><code>unmerger_unlink_sym_post</code></li>
    <li><code>unmerger_unlink_misc_pre</code></li>
    <li><code>unmerger_unlink_misc_post</code></li>
</ul>

<p>The <code>UNLINK_TARGET</code> environment variable specifies the file about
to be unlinked, and <code>ROOT</code> is the filesystem root.</p>

<h2>User Defined Hooks</h2>

<p>User defined hooks should be files named <code>*.bash</code>, <code>*.hook</code>,
<code>*.py</code> or <code>*.so</code>. <code>.bash</code> and <code>.hook</code>
scripts should be executable (<code>chmod a+x</code>). They can live in three locations
(or be symlinked there, to allow a single script to be shared between hooks):</p>

<ul>
    <li><code><em>confdir</em>/hooks/<em>hookname</em>/</code>, where
    <code><em>confdir</em></code> is the directory in which <code>use.conf</code>
    et al. reside.</li>

    <li><code><em>DATADIR</em>/paludis/hooks/<em>hookname</em>/</code>. On most
    systems, <code><em>DATADIR</em></code> is <code>/usr/share</code>.</li>

    <li><code><em>LIBDIR</em>/paludis/hooks/<em>hookname</em>/</code>. On most
    systems, <code><em>LIBDIR</em></code> is <code>/usr/lib</code> or <code>/usr/lib64</code>.</li>
</ul>

<p>For <code>.hook</code> and <code>.so</code> hooks, rather than using <code><em>hookname</em></code>, the
<code>auto</code> directory may be used. In this case, Paludis will ask the hook for which hook names it should be
run.</p>

<h3 id="bash-hooks">Bash Hooks</h3>

<p>A <code>.bash</code> hook is merely executed when the associated action is
triggered. There is no guarantee as to execution order.</p>

<h3 id="hook-hooks">Hook Hooks</h3>

<p>A <code>.hook</code> hook is more powerful. It must not run anything in
global scope, but instead defines all its actions in functions. It must, at
minimum, define a function called <code>hook_run_$HOOK</code> for each hook
that it can handle. It may also define functions called <code>hook_depend_$HOOK</code>,
which should output names of any other hooks upon which it depends, and
<code>hook_after_$HOOK</code>, which is similar but indicates an ordering
rather than hard dependency (the named hooks not existing is not an error).
For example:</p>

<pre>
#!/usr/bin/env bash

hook_run_install_all_post()
{
    # ensure that einfo etc are available
    export PATH="$(${PALUDIS_EBUILD_DIR}/utils/canonicalise ${PALUDIS_EBUILD_DIR}/utils/ ):${PATH}"
    source ${PALUDIS_EBUILD_DIR}/echo_functions.bash

    echo
    einfo "Checking for monkeys..."

    if [[ -d "${ROOT}/var/lib/monkeys" ]] ; then
        for m in "${ROOT}"/var/lib/monkeys/* ; do
            ewarn "Found monkey $(basename "${m}" )"
        done
    else
        einfo "No monkeys found"
    fi
}

hook_depend_install_all_post()
{
    # we need to run after the Paludis standard eselect_env_update hook
    echo eselect_env_update
}

hook_after_install_all_post()
{
    # if checking for rabbits or squirrels, do those first
    echo check_for_rabbits check_for_squirrels
}
</pre>

<p>If the hook is located in an <code>auto</code> directory, the <code>hook_auto_names</code> function must also be
provided. This function should output the hook names under which the hook should be run. For example:</p>

<pre>
hook_auto_names() {
    echo install_all_pre install_all_post
}
</pre>

<p>Note that the <code>hook_depend_</code>, <code>hook_after_</code> and <code>hook_auto_names</code> functions are
cached, and are generally only called once per session, so the output should not vary based upon outside parameters.</p>

<h3 id="py-hooks">Python Hooks</h3>

<p>A <code>.py</code> hook is much like <code>.hook</code> hook, but written
in Python and with full access to the current Paludis environment through
Python bindings. For each hook it can handle it must, at minimum, define
a function named <code>hook_run_$HOOK</code> which accepts exactly two positional
arguments: the current Environment used by Paludis, and the additional Hook environment variables
represented by a Python dictionary. It may also define the <code>hook_depend_$HOOK</code>
and <code>hook_after_$HOOK</code> functions which must take exactly one argument,
the Hook environment, and return a list of strings.
For example:</p>

<pre>
def hook_run_install_all_post(env, hook_env):
    from paludis import *

    print "* Checking for monkeys..."

    if list(env[Selection.SomeArbitraryVersion(Generator.Package("nice/monkey"))]):
        print "Found a monkey!"
    else:
        print "No monkeys found"

def hook_depend_install_all_post(hook_env):
    # we need to run after the Paludis standard eselect_env_update hook
    return ["eselect_env_update"]

def hook_after_install_all_post(hook_env):
    # if checking for rabbits or squirrels, do those first
    return ["check_for_rabbits", "check_for_squirrels"]
</pre>

<h3 id="so-hooks">.so Hooks</h3>

<p>A <code>.so</code> hook is written in C++ and has full access to the Paludis public API.
The hook takes the form of a shared library with a filename ending in <code>.so.<i>N</i></code>,
where <i>N</i> is the first component of the Paludis version number multiplied by 100,
plus the second component of the version number (for example, 26 for Paludis 0.26.x,
or 102 for Paludis 1.2.y).  The library must export a function with prototype
<code>paludis::HookResult paludis_hook_run_3(const paludis::Environment *,
    const paludis::Hook &amp;, const std::shared_ptr&lt;paludis::OutputManager&gt; &amp;)</code>
that performs the action, and optionally one with prototype
<code>void paludis_hook_add_dependencies(const paludis::Environment *, const paludis::Hook &amp;,
    paludis::DirectedGraph&lt;std::string, int&gt; &amp;)</code>
if it needs to define ordering dependencies with other hooks. If the hook is to be placed in an <code>auto</code>
directory, it must also define <code>const std::tr1::shared_ptr&lt;const Sequence&lt;std::string&gt; &gt;
paludis_hook_auto_phases(const paludis::Environment *)</code>. All functions are
declared in the header <code>&lt;paludis/hook.hh&gt;</code>, including any necessary
<code>extern</code> or visibility declarations.</p>

<p>The parameters and return values have the following meanings:</p>
<dl>
<dt><code>const paludis::Environment *</code></dt>
<dd>The usual <code>Environment</code>, as used by all Paludis clients.</dd>
<dt><code>const paludis::Hook &amp;</code></dt>
<dd>Contains information about the hook being called.  In <code>paludis_hook_add_dependencies</code>,
the only useful member is <code>name()</code>.</dd>
<dt><code>const std::shared_ptr&lt;paludis::OutputManager&gt; &amp;</code></dt>
<dd>The output manager being used when the hook is run. Will sometimes be a null pointer, as not all hooks are run with
output managed -- in this case, use of stdout is normal.</dd>
<dt><code>paludis::DirectedGraph&lt;std::string, int&gt; &amp;</code></dt>
<dd>A graph containing, as nodes, all named hooks that will be executed along with
this one.  The <code>paludis_hook_add_dependencies</code> function should add any
edges required to indicate its desired execution order relative to the other hooks,
as follows: <code>g.add_edge("after", "before", 0);</code> (the 0 is not significant,
but required by the <code>DirectedGraph</code> API).</dd>
<dt><code>paludis::HookResult</code></dt>
<dd>The <code>HookResult</code> constructor takes two arguments: an <code>int</code>,
which should be zero if the hook is successful, or positive if not, and a <code>std::string</code>
containing any information that should be passed back to the hook's caller (only
used if the <code>Hook</code>'s <code>output_dest</code> member is <code>hod_grab</code>).</dd>
</dl>

<h2>Package Manager Defined Hooks</h2>

<p>Paludis places some of its own hooks in
<code><em>LIBEXECDIR</em>/hooks/<em>hookname</em></code>. These directories are
not for end user use.</p>

<h2>The <code>PALUDIS_CMDLINE</code> Variables</h2>

<p>Sometimes hooks need access to the commandline used to invoke
<code>paludis</code>.  However, manual parsing of the commandline by hooks will
lead to bugs when people forget to emulate certain behaviour (say, short
options, aliases or <code>--</code> support).  To work around this issue,
Paludis provides environment variables prefixed <code>PALUDIS_CMDLINE_</code>
that specify the parsed command line:</p>

<ul>
    <li>The <code>PALUDIS_CMDLINE_PARAMS</code> variable contains the parameters (that is,
    the parts that aren't <code>-x</code> or <code>--blah</code> or values for these).</li>

    <li>For each <code>--param-name</code>, <code>PALUDIS_CMDLINE_param_name</code> (note
    the case and the underscores) is set. If <code>--param-name</code> takes an argument,
    this argument is used for the environment variable's value.</li>

    <li>For short options (<code>-x</code>) and aliases, the appropriate long option's
    variable is set instead.</li>
</ul>