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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_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>
                <refpurpose>Determine session, service, 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_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>
                </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. 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) 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. (More specifically: this call will
                not work for processes that are part of user units,
                use <function>sd_pid_get_user_unit()</function> for
                that.) 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) 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 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.</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.</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>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> and
                <function>sd_peer_get_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.</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>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_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> and
                <function>sd_peer_get_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>
