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  </style><a href="index.html">Index </a>·
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  <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 204</span><hr><div class="refentry"><a name="sd_pid_get_session"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_pid_get_session, sd_pid_get_unit, sd_pid_get_user_unit, sd_pid_get_owner_uid, sd_pid_get_machine_name — Determine session, service, owner of a session or container/VM of a specific PID</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include &lt;systemd/sd-login.h&gt;</pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_pid_get_session</b>(</code></td><td>pid_t <var class="pdparam">pid</var>, </td></tr><tr><td> </td><td>char** <var class="pdparam">session</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_pid_get_unit</b>(</code></td><td>pid_t <var class="pdparam">pid</var>, </td></tr><tr><td> </td><td>char** <var class="pdparam">unit</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_pid_get_user_unit</b>(</code></td><td>pid_t <var class="pdparam">pid</var>, </td></tr><tr><td> </td><td>char** <var class="pdparam">unit</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_pid_get_owner_uid</b>(</code></td><td>pid_t <var class="pdparam">pid</var>, </td></tr><tr><td> </td><td>uid_t* <var class="pdparam">uid</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_pid_get_machine_name</b>(</code></td><td>pid_t <var class="pdparam">pid</var>, </td></tr><tr><td> </td><td>char** <var class="pdparam">name</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm259781218496"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description"></a></h2><p><code class="function">sd_pid_get_session()</code> 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
                <a href="free.html"><span class="citerefentry"><span class="refentrytitle">free</span>(3)</span></a>
                call after use.</p><p><code class="function">sd_pid_get_unit()</code> 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 <code class="function">sd_pid_get_user_unit()</code> for
                that.) The returned string needs to be freed with the
                libc
                <a href="free.html"><span class="citerefentry"><span class="refentrytitle">free</span>(3)</span></a>
                call after use.</p><p><code class="function">sd_pid_get_user_unit()</code> 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
                <code class="function">sd_pid_get_unit()</code> but applies to
                user units instead of system units.</p><p><code class="function">sd_pid_get_owner_uid()</code> 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
                <code class="function">sd_pid_get_session()</code> will
                fail. For processes not being part of a login session
                and not being a shared process of a user this function
                will fail.</p><p><code class="function">sd_pid_machine_name()</code> 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
                <a href="free.html"><span class="citerefentry"><span class="refentrytitle">free</span>(3)</span></a>
                call after use.</p><p>If the <code class="literal">pid</code> parameter of any
                of these functions is passed as 0 the operation is
                executed for the calling process.</p></div><div class="refsect1"><a name="idm259785104832"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value"></a></h2><p>On success these calls return 0 or a positive
                integer. On failure, these calls return a negative
                errno-style error code.</p></div><div class="refsect1"><a name="idm259785103472"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes"></a></h2><p>The <code class="function">sd_pid_get_session()</code>,
                <code class="function">sd_pid_get_unit()</code>,
                <code class="function">sd_pid_get_user_unit()</code>,
                <code class="function">sd_pid_get_owner_uid()</code> and
                <code class="function">sd_pid_get_machine_name()</code>
                interfaces are available as shared library, which can
                be compiled and linked to with the
                <code class="literal">libsystemd-login</code>
                <a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
                file.</p><p>Note that the login session identifier as
                returned by <code class="function">sd_pid_get_session()</code>
                is completely unrelated to the process session
                identifier as returned by
                <a href="getsid.html"><span class="citerefentry"><span class="refentrytitle">getsid</span>(2)</span></a>.</p></div><div class="refsect1"><a name="idm259785087648"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also"></a></h2><p>
                        <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
                        <a href="sd-login.html"><span class="citerefentry"><span class="refentrytitle">sd-login</span>(3)</span></a>,
                        <a href="sd_session_is_active.html"><span class="citerefentry"><span class="refentrytitle">sd_session_is_active</span>(3)</span></a>,
                        <a href="getsid.html"><span class="citerefentry"><span class="refentrytitle">getsid</span>(2)</span></a>
                </p></div></div></body></html>