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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 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) 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 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 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>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>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_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>