man/sd_bus_creds_get_pid.xml

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  23
  24 <refentry id="sd_bus_creds_get_pid">
  25
  26   <refentryinfo>
  27     <title>sd_bus_creds_get_pid</title>
  28     <productname>systemd</productname>
  29
  30     <authorgroup>
  31       <author>
  32         <contrib>A monkey with a typewriter</contrib>
  33         <firstname>Zbigniew</firstname>
  34         <surname>Jędrzejewski-Szmek</surname>
  35         <email>zbyszek@in.waw.pl</email>
  36       </author>
  37     </authorgroup>
  38   </refentryinfo>
  39
  40   <refmeta>
  41     <refentrytitle>sd_bus_creds_get_pid</refentrytitle>
  42     <manvolnum>3</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>sd_bus_creds_get_pid</refname>
  47     <refname>sd_bus_creds_get_ppid</refname>
  48     <refname>sd_bus_creds_get_tid</refname>
  49     <refname>sd_bus_creds_get_uid</refname>
  50     <refname>sd_bus_creds_get_euid</refname>
  51     <refname>sd_bus_creds_get_suid</refname>
  52     <refname>sd_bus_creds_get_fsuid</refname>
  53     <refname>sd_bus_creds_get_gid</refname>
  54     <refname>sd_bus_creds_get_egid</refname>
  55     <refname>sd_bus_creds_get_sgid</refname>
  56     <refname>sd_bus_creds_get_fsgid</refname>
  57     <refname>sd_bus_creds_get_supplementary_gids</refname>
  58     <refname>sd_bus_creds_get_comm</refname>
  59     <refname>sd_bus_creds_get_tid_comm</refname>
  60     <refname>sd_bus_creds_get_exe</refname>
  61     <refname>sd_bus_creds_get_cmdline</refname>
  62     <refname>sd_bus_creds_get_cgroup</refname>
  63     <refname>sd_bus_creds_get_unit</refname>
  64     <refname>sd_bus_creds_get_slice</refname>
  65     <refname>sd_bus_creds_get_user_unit</refname>
  66     <refname>sd_bus_creds_get_user_slice</refname>
  67     <refname>sd_bus_creds_get_session</refname>
  68     <refname>sd_bus_creds_get_owner_uid</refname>
  69     <refname>sd_bus_creds_has_effective_cap</refname>
  70     <refname>sd_bus_creds_has_permitted_cap</refname>
  71     <refname>sd_bus_creds_has_inheritable_cap</refname>
  72     <refname>sd_bus_creds_has_bounding_cap</refname>
  73     <refname>sd_bus_creds_get_selinux_context</refname>
  74     <refname>sd_bus_creds_get_audit_session_id</refname>
  75     <refname>sd_bus_creds_get_audit_login_uid</refname>
  76     <refname>sd_bus_creds_get_tty</refname>
  77     <refname>sd_bus_creds_get_unique_name</refname>
  78     <refname>sd_bus_creds_get_well_known_names</refname>
  79     <refname>sd_bus_creds_get_description</refname>
  80
  81     <refpurpose>Retrieve fields from a credentials object</refpurpose>
  82   </refnamediv>
  83
  84   <refsynopsisdiv>
  85     <funcsynopsis>
  86       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  87
  88       <funcprototype>
  89         <funcdef>int <function>sd_bus_creds_get_pid</function></funcdef>
  90         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
  91         <paramdef>pid_t *<parameter>pid</parameter></paramdef>
  92       </funcprototype>
  93
  94       <funcprototype>
  95         <funcdef>int <function>sd_bus_creds_get_ppid</function></funcdef>
  96         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
  97         <paramdef>pid_t *<parameter>ppid</parameter></paramdef>
  98       </funcprototype>
  99
 100       <funcprototype>
 101         <funcdef>int <function>sd_bus_creds_get_tid</function></funcdef>
 102         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 103         <paramdef>pid_t *<parameter>tid</parameter></paramdef>
 104       </funcprototype>
 105
 106       <funcprototype>
 107         <funcdef>int <function>sd_bus_creds_get_uid</function></funcdef>
 108         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 109         <paramdef>uid_t *<parameter>uid</parameter></paramdef>
 110       </funcprototype>
 111
 112       <funcprototype>
 113         <funcdef>int <function>sd_bus_creds_get_euid</function></funcdef>
 114         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 115         <paramdef>uid_t *<parameter>uid</parameter></paramdef>
 116       </funcprototype>
 117
 118       <funcprototype>
 119         <funcdef>int <function>sd_bus_creds_get_suid</function></funcdef>
 120         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 121         <paramdef>uid_t *<parameter>uid</parameter></paramdef>
 122       </funcprototype>
 123
 124       <funcprototype>
 125         <funcdef>int <function>sd_bus_creds_get_fsuid</function></funcdef>
 126         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 127         <paramdef>uid_t *<parameter>uid</parameter></paramdef>
 128       </funcprototype>
 129
 130       <funcprototype>
 131         <funcdef>int <function>sd_bus_creds_get_gid</function></funcdef>
 132         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 133         <paramdef>gid_t *<parameter>gid</parameter></paramdef>
 134       </funcprototype>
 135
 136       <funcprototype>
 137         <funcdef>int <function>sd_bus_creds_get_egid</function></funcdef>
 138         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 139         <paramdef>gid_t *<parameter>gid</parameter></paramdef>
 140       </funcprototype>
 141
 142       <funcprototype>
 143         <funcdef>int <function>sd_bus_creds_get_sgid</function></funcdef>
 144         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 145         <paramdef>gid_t *<parameter>gid</parameter></paramdef>
 146       </funcprototype>
 147
 148       <funcprototype>
 149         <funcdef>int <function>sd_bus_creds_get_fsgid</function></funcdef>
 150         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 151         <paramdef>gid_t *<parameter>gid</parameter></paramdef>
 152       </funcprototype>
 153
 154       <funcprototype>
 155         <funcdef>int <function>sd_bus_creds_get_supplementary_gids</function></funcdef>
 156         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 157         <paramdef>const gid_t **<parameter>gids</parameter></paramdef>
 158       </funcprototype>
 159
 160       <funcprototype>
 161         <funcdef>int <function>sd_bus_creds_get_comm</function></funcdef>
 162         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 163         <paramdef>const char **<parameter>comm</parameter></paramdef>
 164       </funcprototype>
 165
 166       <funcprototype>
 167         <funcdef>int <function>sd_bus_creds_get_tid_comm</function></funcdef>
 168         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 169         <paramdef>const char **<parameter>comm</parameter></paramdef>
 170       </funcprototype>
 171
 172       <funcprototype>
 173         <funcdef>int <function>sd_bus_creds_get_exe</function></funcdef>
 174         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 175         <paramdef>const char **<parameter>exe</parameter></paramdef>
 176       </funcprototype>
 177
 178       <funcprototype>
 179         <funcdef>int <function>sd_bus_creds_get_cmdline</function></funcdef>
 180         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 181         <paramdef>char ***<parameter>cmdline</parameter></paramdef>
 182       </funcprototype>
 183
 184       <funcprototype>
 185         <funcdef>int <function>sd_bus_creds_get_cgroup</function></funcdef>
 186         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 187         <paramdef>const char **<parameter>cgroup</parameter></paramdef>
 188       </funcprototype>
 189
 190       <funcprototype>
 191         <funcdef>int <function>sd_bus_creds_get_unit</function></funcdef>
 192         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 193         <paramdef>const char **<parameter>unit</parameter></paramdef>
 194       </funcprototype>
 195
 196       <funcprototype>
 197         <funcdef>int <function>sd_bus_creds_get_slice</function></funcdef>
 198         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 199         <paramdef>const char **<parameter>slice</parameter></paramdef>
 200       </funcprototype>
 201
 202       <funcprototype>
 203         <funcdef>int <function>sd_bus_creds_get_user_unit</function></funcdef>
 204         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 205         <paramdef>const char **<parameter>unit</parameter></paramdef>
 206       </funcprototype>
 207
 208       <funcprototype>
 209         <funcdef>int <function>sd_bus_creds_get_user_slice</function></funcdef>
 210         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 211         <paramdef>const char **<parameter>slice</parameter></paramdef>
 212       </funcprototype>
 213
 214       <funcprototype>
 215         <funcdef>int <function>sd_bus_creds_get_session</function></funcdef>
 216         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 217         <paramdef>const char **<parameter>slice</parameter></paramdef>
 218       </funcprototype>
 219
 220       <funcprototype>
 221         <funcdef>int <function>sd_bus_creds_get_owner_uid</function></funcdef>
 222         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 223         <paramdef>uid_t *<parameter>uid</parameter></paramdef>
 224       </funcprototype>
 225
 226       <funcprototype>
 227         <funcdef>int <function>sd_bus_creds_has_effective_cap</function></funcdef>
 228         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 229         <paramdef>int <parameter>capability</parameter></paramdef>
 230       </funcprototype>
 231
 232       <funcprototype>
 233         <funcdef>int <function>sd_bus_creds_has_permitted_cap</function></funcdef>
 234         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 235         <paramdef>int <parameter>capability</parameter></paramdef>
 236       </funcprototype>
 237
 238       <funcprototype>
 239         <funcdef>int <function>sd_bus_creds_has_inheritable_cap</function></funcdef>
 240         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 241         <paramdef>int <parameter>capability</parameter></paramdef>
 242       </funcprototype>
 243
 244       <funcprototype>
 245         <funcdef>int <function>sd_bus_creds_has_bounding_cap</function></funcdef>
 246         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 247         <paramdef>int <parameter>capability</parameter></paramdef>
 248       </funcprototype>
 249
 250       <funcprototype>
 251         <funcdef>int <function>sd_bus_creds_get_selinux_context</function></funcdef>
 252         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 253         <paramdef>const char **<parameter>context</parameter></paramdef>
 254       </funcprototype>
 255
 256       <funcprototype>
 257         <funcdef>int <function>sd_bus_creds_get_audit_session_id</function></funcdef>
 258         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 259         <paramdef>uint32_t *<parameter>sessionid</parameter></paramdef>
 260       </funcprototype>
 261
 262       <funcprototype>
 263         <funcdef>int <function>sd_bus_creds_get_audit_login_uid</function></funcdef>
 264         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 265         <paramdef>uid_t *<parameter>loginuid</parameter></paramdef>
 266       </funcprototype>
 267
 268       <funcprototype>
 269         <funcdef>int <function>sd_bus_creds_get_tty</function></funcdef>
 270         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 271         <paramdef>const char **<parameter>tty</parameter></paramdef>
 272       </funcprototype>
 273
 274       <funcprototype>
 275         <funcdef>int <function>sd_bus_creds_get_unique_name</function></funcdef>
 276         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 277         <paramdef>const char **<parameter>name</parameter></paramdef>
 278       </funcprototype>
 279
 280       <funcprototype>
 281         <funcdef>int <function>sd_bus_creds_get_well_known_names</function></funcdef>
 282         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 283         <paramdef>char ***<parameter>name</parameter></paramdef>
 284       </funcprototype>
 285
 286       <funcprototype>
 287         <funcdef>int <function>sd_bus_creds_get_description</function></funcdef>
 288         <paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
 289         <paramdef>const char **<parameter>name</parameter></paramdef>
 290       </funcprototype>
 291
 292     </funcsynopsis>
 293   </refsynopsisdiv>
 294
 295   <refsect1>
 296     <title>Description</title>
 297
 298     <para>These functions return credential information from an
 299     <parameter>sd_bus_creds</parameter> object. Credential objects may
 300     be created with
 301     <citerefentry><refentrytitle>sd_bus_creds_new_from_pid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 302     in which case they describe the credentials of the process
 303     identified by the specified PID, with
 304     <citerefentry><refentrytitle>sd_bus_get_name_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 305     in which case they describe the credentials of a bus peer
 306     identified by the specified bus name, with
 307     <citerefentry><refentrytitle>sd_bus_get_owner_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 308     in which case they describe the credentials of the creator of a
 309     bus, or with
 310     <citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 311     in which case they describe the credentials of the sender of the
 312     message.</para>
 313
 314     <para>Not all credential fields are part of every
 315     <literal>sd_bus_creds</literal> object. Use
 316     <citerefentry><refentrytitle>sd_bus_creds_get_mask</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 317     to determine the mask of fields available.</para>
 318
 319     <para><function>sd_bus_creds_get_pid()</function> will retrieve
 320     the PID (process identifier). Similarly,
 321     <function>sd_bus_creds_get_ppid()</function> will retrieve the
 322     parent PID. Note that PID 1 has no parent process, in which case
 323     -ENXIO is returned.</para>
 324
 325     <para><function>sd_bus_creds_get_tid()</function> will retrieve the
 326     TID (thread identifier).</para>
 327
 328     <para><function>sd_bus_creds_get_uid()</function> will retrieve
 329     the numeric UID (user identifier). Similarly,
 330     <function>sd_bus_creds_get_euid()</function> returns the effective
 331     UID, <function>sd_bus_creds_get_suid()</function> the saved UID
 332     and <function>sd_bus_creds_get_fsuid()</function> the file system
 333     UID.</para>
 334
 335     <para><function>sd_bus_creds_get_gid()</function> will retrieve the
 336     numeric GID (group identifier). Similarly,
 337     <function>sd_bus_creds_get_egid()</function> returns the effective
 338     GID, <function>sd_bus_creds_get_sgid()</function> the saved GID
 339     and <function>sd_bus_creds_get_fsgid()</function> the file system
 340     GID.</para>
 341
 342     <para><function>sd_bus_creds_get_supplementary_gids()</function>
 343     will retrieve the supplementary GIDs list.</para>
 344
 345     <para><function>sd_bus_creds_get_comm()</function> will retrieve the
 346     comm field (truncated name of the executable, as stored in
 347     <filename>/proc/<replaceable>pid</replaceable>/comm</filename>).
 348     </para>
 349
 350     <para><function>sd_bus_creds_get_tid_comm()</function> will retrieve
 351     the comm field of the thread (as stored in
 352     <filename>/proc/<replaceable>pid</replaceable>/task/<replaceable>tid</replaceable>/comm</filename>).
 353     </para>
 354
 355     <para><function>sd_bus_creds_get_exe()</function> will retrieve
 356     the path to the program executable (as stored in the
 357     <filename>/proc/<replaceable>pid</replaceable>/exe</filename>
 358     link, but with the <literal> (deleted)</literal> suffix removed). Note
 359     that kernel threads do not have an executable path, in which case
 360     -ENXIO is returned.</para>
 361
 362     <para><function>sd_bus_creds_get_cmdline()</function> will
 363     retrieve an array of command line arguments (as stored in
 364     <filename>/proc/<replaceable>pid</replaceable>/cmdline</filename>). Note
 365     that kernel threads do not have a command line, in which case
 366     -ENXIO is returned.</para>
 367
 368     <para><function>sd_bus_creds_get_cgroup()</function> will retrieve
 369     the cgroup path. See <ulink
 370     url="https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>.
 371     </para>
 372
 373     <para><function>sd_bus_creds_get_unit()</function> will retrieve
 374     the systemd unit name (in the system instance of systemd) that the
 375     process is a part of. See
 376     <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. For
 377     processes that are not part of a unit, returns -ENXIO.
 378     </para>
 379
 380     <para><function>sd_bus_creds_get_user_unit()</function> will
 381     retrieve the systemd unit name (in the user instance of systemd)
 382     that the process is a part of. See
 383     <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. For
 384     processes that are not part of a user unit, returns -ENXIO.
 385     </para>
 386
 387     <para><function>sd_bus_creds_get_slice()</function> will retrieve
 388     the systemd slice (a unit in the system instance of systemd) that
 389     the process is a part of. See
 390     <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Similarly,
 391     <function>sd_bus_creds_get_user_slice()</function> retrieves the
 392     systemd slice of the process, in the user instance of systemd.
 393     </para>
 394
 395     <para><function>sd_bus_creds_get_session()</function> will
 396     retrieve the identifier of the login session that the process is
 397     a part of. See
 398     <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>. For
 399     processes that are not part of a session, returns -ENXIO.
 400     </para>
 401
 402     <para><function>sd_bus_creds_get_owner_uid()</function> will
 403     retrieve the numeric UID (user identifier) of the user who owns
 404     the login session that the process is a part of. See
 405     <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 406     For processes that are not part of a session, returns -ENXIO.
 407     </para>
 408
 409     <para><function>sd_bus_creds_has_effective_cap()</function> will
 410     check whether the capability specified by
 411     <parameter>capability</parameter> was set in the effective
 412     capabilities mask. A positive return value means that is was
 413     set, zero means that it was not set, and a negative return
 414     value indicates an error. See
 415     <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 416     and <varname>Capabilities=</varname> and
 417     <varname>CapabilityBoundingSet=</varname> settings in
 418     <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 419     </para>
 420
 421     <para><function>sd_bus_creds_has_permitted_cap()</function> is
 422     similar to <function>sd_bus_creds_has_effective_cap()</function>,
 423     but will check the permitted capabilities mask.</para>
 424
 425     <para><function>sd_bus_creds_has_inheritable_cap()</function> is
 426     similar to <function>sd_bus_creds_has_effective_cap()</function>,
 427     but will check the inheritable capabilities mask.</para>
 428
 429     <para><function>sd_bus_creds_has_bounding_cap()</function> is
 430     similar to <function>sd_bus_creds_has_effective_cap()</function>,
 431     but will check the bounding capabilities mask.</para>
 432
 433     <para><function>sd_bus_creds_get_selinux_context()</function> will
 434     retrieve the SELinux security context (label) of the process.</para>
 435
 436     <para><function>sd_bus_creds_get_audit_session_id()</function>
 437     will retrieve the audit session identifier of the process. Returns
 438     -ENXIO for processes that are not part of an audit session.</para>
 439
 440     <para><function>sd_bus_creds_get_audit_login_uid()</function> will
 441     retrieve the audit user login identifier (the identifier of the
 442     user who is "responsible" for the session). Returns -ENXIO for
 443     processes that are not part of an audit session.</para>
 444
 445     <para><function>sd_bus_creds_get_tty()</function> will retrieve
 446     the controlling TTY, without the prefixing "/dev/". Returns -ENXIO
 447     for processes that have no controlling TTY.</para>
 448
 449     <para><function>sd_bus_creds_get_unique_name()</function> will
 450     retrieve the D-Bus unique name. See <ulink
 451     url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names-bus">The
 452     D-Bus specification</ulink>.</para>
 453
 454     <para><function>sd_bus_creds_get_well_known_names()</function> will
 455     retrieve the set of D-Bus well-known names. See <ulink
 456     url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names-bus">The
 457     D-Bus specification</ulink>.</para>
 458
 459     <para><function>sd_bus_creds_get_description()</function> will
 460     retrieve a descriptive name of the bus connection of the
 461     peer. This name is useful to discern multiple bus connections by
 462     the same peer, and may be altered by the peer with the
 463     <citerefentry><refentrytitle>sd_bus_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 464     call.</para>
 465
 466     <para>All functions that take a <parameter>const
 467     char**</parameter> parameter will store the answer there as an
 468     address of a NUL-terminated string. It will be valid as long as
 469     <parameter>c</parameter> remains valid, and should not be freed or
 470     modified by the caller.</para>
 471
 472     <para>All functions that take a <parameter>char***</parameter>
 473     parameter will store the answer there as an address of a an array
 474     of strings. Each individual string is NUL-terminated, and the
 475     array is NULL-terminated as a whole. It will be valid as long as
 476     <parameter>c</parameter> remains valid, and should not be freed or
 477     modified by the caller.</para>
 478   </refsect1>
 479
 480   <refsect1>
 481     <title>Return Value</title>
 482
 483     <para>On success, these calls return 0 or a positive integer. On
 484     failure, these calls return a negative errno-style error code.
 485     </para>
 486   </refsect1>
 487
 488   <refsect1>
 489     <title>Errors</title>
 490
 491     <para>Returned errors may indicate the following problems:</para>
 492
 493     <variablelist>
 494       <varlistentry>
 495         <term><constant>-ENODATA</constant></term>
 496
 497         <listitem><para>The given field is not available in the
 498         credentials object <parameter>c</parameter>.</para>
 499         </listitem>
 500       </varlistentry>
 501
 502       <varlistentry>
 503         <term><constant>-ENXIO</constant></term>
 504
 505         <listitem><para>The given field is not specified for the described
 506         process or peer. This will be returned by
 507         <function>sd_bus_get_unit()</function>,
 508         <function>sd_bus_get_slice()</function>,
 509         <function>sd_bus_get_user_unit()</function>,
 510         <function>sd_bus_get_user_slice()</function>,
 511         <function>sd_bus_get_session()</function>, and
 512         <function>sd_bus_get_owner_uid()</function> if the process is
 513         not part of a systemd system unit, systemd user unit, systemd
 514         slice, or logind session. It will also be returned by
 515         <function>sd_bus_creds_get_exe()</function> and
 516         <function>sd_bus_creds_get_cmdline()</function> for kernel
 517         threads (since these are not started from an executable binary,
 518         nor have a command line), and by
 519         <function>sd_bus_creds_get_audit_session_id()</function> and
 520         <function>sd_bus_creds_get_audit_login_uid()</function> when
 521         the process is not part of an audit session, and
 522         <function>sd_bus_creds_get_tty()</function> if the process has
 523         no controlling TTY.
 524         </para>
 525         </listitem>
 526       </varlistentry>
 527
 528       <varlistentry>
 529         <term><constant>-EINVAL</constant></term>
 530
 531         <listitem><para>Specified pointer parameter is <constant>NULL</constant>.
 532         </para></listitem>
 533       </varlistentry>
 534
 535       <varlistentry>
 536         <term><constant>-ENOMEM</constant></term>
 537
 538         <listitem><para>Memory allocation failed.</para></listitem>
 539       </varlistentry>
 540     </variablelist>
 541   </refsect1>
 542
 543   <refsect1>
 544     <title>Notes</title>
 545
 546     <para><function>sd_bus_creds_get_pid()</function> and the other
 547     functions described here are available as a shared library, which
 548     can be compiled and linked to with the
 549     <constant>libsystemd</constant> <citerefentry
 550     project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 551     file.</para>
 552   </refsect1>
 553
 554   <refsect1>
 555     <title>See Also</title>
 556
 557     <para>
 558       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 559       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 560       <citerefentry><refentrytitle>sd_bus_creds_new_from_pid</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 561       <citerefentry project='man-pages'><refentrytitle>fork</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 562       <citerefentry project='man-pages'><refentrytitle>execve</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 563       <citerefentry project='man-pages'><refentrytitle>credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 564       <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 565       <citerefentry project='man-pages'><refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 566       <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 567     </para>
 568   </refsect1>
 569
 570 </refentry>