systemd/man/sd_pid_get_owner_uid.xml

<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1+ -->

<refentry id="sd_pid_get_owner_uid" conditional='HAVE_PAM'
          xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_pid_get_owner_uid</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_pid_get_owner_uid</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_pid_get_owner_uid</refname>
    <refname>sd_pid_get_session</refname>
    <refname>sd_pid_get_user_unit</refname>
    <refname>sd_pid_get_unit</refname>
    <refname>sd_pid_get_machine_name</refname>
    <refname>sd_pid_get_slice</refname>
    <refname>sd_pid_get_user_slice</refname>
    <refname>sd_pid_get_cgroup</refname>
    <refname>sd_peer_get_owner_uid</refname>
    <refname>sd_peer_get_session</refname>
    <refname>sd_peer_get_user_unit</refname>
    <refname>sd_peer_get_unit</refname>
    <refname>sd_peer_get_machine_name</refname>
    <refname>sd_peer_get_slice</refname>
    <refname>sd_peer_get_user_slice</refname>
    <refname>sd_peer_get_cgroup</refname>
    <refpurpose>Determine the owner uid of the user unit or session,
    or the session, user unit, system unit, container/VM or slice that
    a specific PID or socket peer belongs to.</refpurpose>
  </refnamediv>

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

      <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_session</function></funcdef>
        <paramdef>pid_t <parameter>pid</parameter></paramdef>
        <paramdef>char **<parameter>session</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_unit</function></funcdef>
        <paramdef>pid_t <parameter>pid</parameter></paramdef>
        <paramdef>char **<parameter>unit</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_pid_get_cgroup</function></funcdef>
        <paramdef>pid_t <parameter>pid</parameter></paramdef>
        <paramdef>char **<parameter>cgroup</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_session</function></funcdef>
        <paramdef>int <parameter>fd</parameter></paramdef>
        <paramdef>char **<parameter>session</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_unit</function></funcdef>
        <paramdef>int <parameter>fd</parameter></paramdef>
        <paramdef>char **<parameter>unit</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>

      <funcprototype>
        <funcdef>int <function>sd_peer_get_cgroup</function></funcdef>
        <paramdef>int <parameter>fd</parameter></paramdef>
        <paramdef>char **<parameter>cgroup</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_pid_get_owner_uid()</function> may be used to
    determine the Unix UID (user identifier) which owns the login
    session or systemd user unit of a process identified by the
    specified PID. For processes which are not part of a login session
    and not managed by a user manager, this function will fail with
    <constant>-ENODATA</constant>.</para>

    <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. Please
    note the login session may be limited to a stub process or two.
    User processes may instead be started from their systemd user
    manager, e.g. GUI applications started using DBus activation, as
    well as service processes which are shared between multiple logins
    of the same user. For processes which are not part of a login
    session, this function will fail with <constant>-ENODATA</constant>.
    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. The
    unit name is a short string, suitable for usage in file system
    paths. For processes which are not managed by a user manager, this
    function will fail with <constant>-ENODATA</constant>. 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. For processes not being part of a systemd system
    unit, this function will fail with <constant>-ENODATA</constant>.
    (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_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 container, this
    function fails with <constant>-ENODATA</constant>.</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>Similarly, <function>sd_pid_get_user_slice()</function>
    returns the user slice (as managed by the user's systemd instance)
    of a process.</para>

    <para><function>sd_pid_get_cgroup()</function> returns the control
    group path of the specified process, relative to the root of the
    hierarchy. Returns the path without trailing slash, except for
    processes located in the root control group, where "/" is
    returned. To find the actual control group path in the file system,
    the returned path needs to be prefixed with
    <filename>/sys/fs/cgroup/</filename> (if the unified control group
    setup is used), or
    <filename>/sys/fs/cgroup/<replaceable>HIERARCHY</replaceable>/</filename>
    (if the legacy multi-hierarchy control group setup is used).</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_owner_uid()</function>,
    <function>sd_peer_get_session()</function>,
    <function>sd_peer_get_user_unit()</function>,
    <function>sd_peer_get_unit()</function>,
    <function>sd_peer_get_machine_name()</function>,
    <function>sd_peer_get_slice()</function>,
    <function>sd_peer_get_user_slice()</function> and
    <function>sd_peer_get_cgroup()</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>

    <refsect2>
      <title>Errors</title>

      <para>Returned errors may indicate the following problems:</para>

      <variablelist>

        <varlistentry>
          <term><constant>-ESRCH</constant></term>

          <listitem><para>The specified PID does not refer to a running process.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-EBADF</constant></term>

          <listitem><para>The specified socket file descriptor was invalid.</para></listitem>
        </varlistentry>

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

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

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

          <listitem><para>An input parameter was invalid (out of range, or <constant>NULL</constant>, where
          that is not accepted).</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ENOMEM</constant></term>

          <listitem><para>Memory allocation failed.</para></listitem>
        </varlistentry>
      </variablelist>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>

    <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>