systemd/man/sd_session_is_active.xml

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<refentry id="sd_session_is_active" conditional='HAVE_PAM'>

  <refentryinfo>
    <title>sd_session_is_active</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_session_is_active</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_session_is_active</refname>
    <refname>sd_session_is_remote</refname>
    <refname>sd_session_get_state</refname>
    <refname>sd_session_get_uid</refname>
    <refname>sd_session_get_seat</refname>
    <refname>sd_session_get_service</refname>
    <refname>sd_session_get_type</refname>
    <refname>sd_session_get_class</refname>
    <refname>sd_session_get_desktop</refname>
    <refname>sd_session_get_display</refname>
    <refname>sd_session_get_tty</refname>
    <refname>sd_session_get_vt</refname>
    <refname>sd_session_get_remote_host</refname>
    <refname>sd_session_get_remote_user</refname>
    <refpurpose>Determine state of a specific session</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int <function>sd_session_is_active</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_is_remote</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_state</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>state</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_uid</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>uid_t *<parameter>uid</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_seat</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>seat</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_service</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>service</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_type</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>type</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_class</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>class</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_desktop</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>desktop</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_display</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>display</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_remote_host</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>remote_host</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_remote_user</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>remote_user</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_tty</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>char **<parameter>tty</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_session_get_vt</function></funcdef>
        <paramdef>const char *<parameter>session</parameter></paramdef>
        <paramdef>unsigned int *<parameter>vt</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_session_is_active()</function> may be used to
    determine whether the session identified by the specified session
    identifier is currently active (i.e. currently in the foreground
    and available for user input) or not.</para>

    <para><function>sd_session_is_remote()</function> may be used to
    determine whether the session identified by the specified session
    identifier is a remote session (i.e. its remote host is known) or
    not.</para>

    <para><function>sd_session_get_state()</function> may be used to
    determine the state of the session identified by the specified
    session identifier. The following states are currently known:
    <literal>online</literal> (session logged in, but session not
    active, i.e. not in the foreground), <literal>active</literal>
    (session logged in and active, i.e. in the foreground),
    <literal>closing</literal> (session nominally logged out, but some
    processes belonging to it are still around). In the future
    additional states might be defined, client code should be written
    to be robust in regards to additional state strings being
    returned. This function is a more generic version of
    <function>sd_session_is_active()</function>. 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_session_get_uid()</function> may be used to
    determine the user identifier of the Unix user the session
    identified by the specified session identifier belongs to.</para>

    <para><function>sd_session_get_seat()</function> may be used to
    determine the seat identifier of the seat the session identified
    by the specified session identifier belongs to. Note that not all
    sessions are attached to a seat, this call will fail (returning
    <constant>-ENODATA</constant>) for them. 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_session_get_service()</function> may be used to
    determine the name of the service (as passed during PAM session
    setup) that registered the session identified by the specified
    session identifier. 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_session_get_type()</function> may be used to
    determine the type of the session identified by the specified
    session identifier. The returned string is one of
    <literal>x11</literal>, <literal>wayland</literal>,
    <literal>tty</literal>, <literal>mir</literal> or
    <literal>unspecified</literal> and 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_session_get_class()</function> may be used to
    determine the class of the session identified by the specified
    session identifier. The returned string is one of
    <literal>user</literal>, <literal>greeter</literal>,
    <literal>lock-screen</literal>, or <literal>background</literal>
    and 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_session_get_desktop()</function> may be used to
    determine the brand of the desktop running on the session
    identified by the specified session identifier. This field can be
    set freely by desktop environments and does not follow any special
    formatting. However, desktops are strongly recommended to use the
    same identifiers and capitalization as for
    <varname>$XDG_CURRENT_DESKTOP</varname>, as defined by the <ulink
    url="http://standards.freedesktop.org/desktop-entry-spec/latest/">Desktop
    Entry Specification</ulink>. 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_session_get_display()</function> may be used to
    determine the X11 display of the session identified by the
    specified session identifier. 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_session_get_remote_host()</function> may be
    used to determine the remote hostname of the session identified by
    the specified session identifier. 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_session_get_remote_user()</function> may be
    used to determine the remote username of the session identified by
    the specified session identifier. The returned string needs to be
    freed with the libc
    <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    call after use. Note that this value is rarely known to the
    system, and even then should not be relied on.</para>

    <para><function>sd_session_get_tty()</function> may be used to
    determine the TTY device of the session identified by the
    specified session identifier. 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_session_get_vt()</function> may be used to
    determine the VT number of the session identified by the specified
    session identifier. This function will return an error if the seat
    does not support VTs.</para>

    <para>If the <varname>session</varname> parameter of any of these
    functions is passed as <constant>NULL</constant>, the operation is
    executed for the session the calling process is a member of, if
    there is any.</para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>If the test succeeds,
    <function>sd_session_is_active()</function> and
    <function>sd_session_is_remote()</function> return a
    positive integer; if it fails, 0.  On success,
    <function>sd_session_get_state()</function>,
    <function>sd_session_get_uid()</function>,
    <function>sd_session_get_seat()</function>,
    <function>sd_session_get_service()</function>,
    <function>sd_session_get_type()</function>,
    <function>sd_session_get_class()</function>,
    <function>sd_session_get_display()</function>,
    <function>sd_session_get_remote_user()</function>,
    <function>sd_session_get_remote_host()</function> and
    <function>sd_session_get_tty()</function> 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>The specified session does not exist.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ENODATA</constant></term>

        <listitem><para>The given field is not specified for the described
        session.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-EINVAL</constant></term>

        <listitem><para>An input parameter was invalid (out of range,
        or NULL, where that is not accepted).</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_session_is_active()</function>,
    <function>sd_session_get_state()</function>,
    <function>sd_session_get_uid()</function>,
    <function>sd_session_get_seat()</function>,
    <function>sd_session_get_service()</function>,
    <function>sd_session_get_type()</function>,
    <function>sd_session_get_class()</function>,
    <function>sd_session_get_display()</function>,
    <function>sd_session_get_remote_host()</function>,
    <function>sd_session_get_remote_user()</function> and
    <function>sd_session_get_tty()</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>
  </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_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>