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systemd/man/sd_pid_get_session.xml

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
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Copyright 2010 Lennart Poettering
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<refentry id="sd_pid_get_session" conditional='HAVE_PAM'>
<refentryinfo>
<title>sd_pid_get_session</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_pid_get_session</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_pid_get_session</refname>
<refname>sd_pid_get_unit</refname>
<refname>sd_pid_get_user_unit</refname>
<refname>sd_pid_get_owner_uid</refname>
<refname>sd_pid_get_machine_name</refname>
<refname>sd_pid_get_slice</refname>
<refname>sd_pid_get_user_slice</refname>
<refname>sd_peer_get_session</refname>
<refname>sd_peer_get_unit</refname>
<refname>sd_peer_get_user_unit</refname>
<refname>sd_peer_get_owner_uid</refname>
<refname>sd_peer_get_machine_name</refname>
<refname>sd_peer_get_slice</refname>
<refname>sd_peer_get_user_slice</refname>
<refpurpose>Determine session, unit, owner of a session,
container/VM or slice of a specific PID or socket
peer</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_pid_get_session</function></funcdef>
<paramdef>pid_t <parameter>pid</parameter></paramdef>
<paramdef>char **<parameter>session</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_pid_get_unit</function></funcdef>
<paramdef>pid_t <parameter>pid</parameter></paramdef>
<paramdef>char **<parameter>unit</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_pid_get_user_unit</function></funcdef>
<paramdef>pid_t <parameter>pid</parameter></paramdef>
<paramdef>char **<parameter>unit</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_pid_get_owner_uid</function></funcdef>
<paramdef>pid_t <parameter>pid</parameter></paramdef>
<paramdef>uid_t *<parameter>uid</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_pid_get_machine_name</function></funcdef>
<paramdef>pid_t <parameter>pid</parameter></paramdef>
<paramdef>char **<parameter>name</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_pid_get_slice</function></funcdef>
<paramdef>pid_t <parameter>pid</parameter></paramdef>
<paramdef>char **<parameter>slice</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_pid_get_user_slice</function></funcdef>
<paramdef>pid_t <parameter>pid</parameter></paramdef>
<paramdef>char **<parameter>slice</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_peer_get_session</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>char **<parameter>session</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_peer_get_unit</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>char **<parameter>unit</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_peer_get_user_unit</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>char **<parameter>unit</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_peer_get_owner_uid</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>uid_t *<parameter>uid</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_peer_get_machine_name</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>char **<parameter>name</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_peer_get_slice</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>char **<parameter>slice</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_peer_get_user_slice</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>char **<parameter>slice</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_pid_get_session()</function> may be used to
determine the login session identifier of a process identified by
the specified process identifier. The session identifier is a
short string, suitable for usage in file system paths. Note that
not all processes are part of a login session (e.g. system service
processes, user processes that are shared between multiple
sessions of the same user, or kernel threads). For processes not
being part of a login session this function will fail with
-ENXIO. The returned string needs to be freed with the libc
<citerefentry
project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
call after use.</para>
<para><function>sd_pid_get_unit()</function> may be used to
determine the systemd system unit (i.e. system service or scope
unit) identifier of a process identified by the specified PID. The
unit name is a short string, suitable for usage in file system
paths. Note that not all processes are part of a system
unit/service (e.g. user processes, or kernel threads). For
processes not being part of a systemd system unit this function
will fail with -ENXIO (More specifically: this call will not work
for kernel threads.) The returned string needs to be freed with
the libc <citerefentry
project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
call after use.</para>
<para><function>sd_pid_get_user_unit()</function> may be used to
determine the systemd user unit (i.e. user service or scope unit)
identifier of a process identified by the specified PID. This is
similar to <function>sd_pid_get_unit()</function> but applies to
user units instead of system units.</para>
<para><function>sd_pid_get_owner_uid()</function> may be used to
determine the Unix UID (user identifier) of the owner of the
session of a process identified the specified PID. Note that this
function will succeed for user processes which are shared between
multiple login sessions of the same user, where
<function>sd_pid_get_session()</function> will fail. For processes
not being part of a login session and not being a shared process
of a user this function will fail with -ENXIO.</para>
<para><function>sd_pid_get_machine_name()</function> may be used
to determine the name of the VM or container is a member of. The
machine name is a short string, suitable for usage in file system
paths. The returned string needs to be freed with the libc
<citerefentry
project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
call after use. For processes not part of a VM or containers this
function fails with -ENXIO.</para>
<para><function>sd_pid_get_slice()</function> may be used to
determine the slice unit the process is a member of. See
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details about slices. The returned string needs to be freed
with the libc
<citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
call after use.</para>
<para>Similar, <function>sd_pid_get_user_slice()</function>
returns the user slice (as managed by the user's systemd instance)
of a process.</para>
<para>If the <varname>pid</varname> parameter of any of these
functions is passed as 0, the operation is executed for the
calling process.</para>
<para>The <function>sd_peer_get_session()</function>,
<function>sd_peer_get_unit()</function>,
<function>sd_peer_get_user_unit()</function>,
<function>sd_peer_get_owner_uid()</function>,
<function>sd_peer_get_machine_name()</function>,
<function>sd_peer_get_slice()</function> and
<function>sd_peer_get_user_slice()</function> calls operate
similar to their PID counterparts, but operate on a connected
AF_UNIX socket and retrieve information about the connected peer
process. Note that these fields are retrieved via
<filename>/proc</filename>, and hence are not suitable for
authorization purposes, as they are subject to races.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, these calls return 0 or a positive integer. On
failure, these calls return a negative errno-style error
code.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-ENXIO</constant></term>
<listitem><para>Given field is not specified for the described
process or peer.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>-ESRCH</constant></term>
<listitem><para>The specified PID does not refer to a running
process.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOMEM</constant></term>
<listitem><para>Memory allocation failed.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Notes</title>
<para>The <function>sd_pid_get_session()</function>,
<function>sd_pid_get_unit()</function>,
<function>sd_pid_get_user_unit()</function>,
<function>sd_pid_get_owner_uid()</function>,
<function>sd_pid_get_machine_name()</function>,
<function>sd_pid_get_slice()</function>,
<function>sd_pid_get_user_slice()</function>,
<function>sd_peer_get_session()</function>,
<function>sd_peer_get_unit()</function>,
<function>sd_peer_get_user_unit()</function>,
<function>sd_peer_get_owner_uid()</function>,
<function>sd_peer_get_machine_name()</function>,
<function>sd_peer_get_slice()</function> and
<function>sd_peer_get_user_slice()</function> interfaces are
available as a shared library, which can be compiled and linked to
with the <constant>libsystemd</constant> <citerefentry
project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
<para>Note that the login session identifier as
returned by <function>sd_pid_get_session()</function>
is completely unrelated to the process session
identifier as returned by
<citerefentry><refentrytitle>getsid</refentrytitle><manvolnum>2</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>getsid</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>