1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
|
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>2017</year><year>2018</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
</legalnotice>
<title>logger</title>
<prepared></prepared>
<responsible></responsible>
<docno></docno>
<approved></approved>
<checked></checked>
<date></date>
<rev>A</rev>
<file>logger.xml</file>
</header>
<module>logger</module>
<modulesummary>API module for Logger, the standard logging facility
in Erlang/OTP.</modulesummary>
<description>
<p>This module implements the main API for logging in
Erlang/OTP. To create a log event, use the
<seealso marker="#logging_API">API functions</seealso> or the
log
<seealso marker="#macros">macros</seealso>, for example:</p>
<code>
?LOG_ERROR("error happened because: ~p", [Reason]). % With macro
logger:error("error happened because: ~p", [Reason]). % Without macro
</code>
<p>To configure the Logger backend,
use <seealso marker="kernel_app#logger">Kernel configuration
parameters</seealso>
or <seealso marker="#configuration_API">configuration
functions</seealso> in the Logger API.</p>
<p>By default, the Kernel application installs one log handler at
system start. This handler is named <c>default</c>. It receives
and processes standard log events produced by the Erlang runtime
system, standard behaviours and different Erlang/OTP
applications. The log events are by default printed to the
terminal.</p>
<p>If you want your systems logs to be printed to a file instead,
you must configure the default handler to do so. The simplest
way is to include the following in
your <seealso marker="config"><c>sys.config</c></seealso>:</p>
<code>
[{kernel,
[{logger,
[{handler, default, logger_std_h,
#{config => #{type => {file, "path/to/file.log"}}}}]}]}].
</code>
<p>
For more information about:
</p>
<list type="bulleted">
<item>the Logger facility in general, see
the <seealso marker="logger_chapter">User's
Guide</seealso>.</item>
<item>how to configure Logger, see
the <seealso marker="logger_chapter#configuration">Configuration</seealso>
section in the User's Guide.</item>
<item>the built-in handlers,
see <seealso marker="logger_std_h">logger_std_h</seealso> and
<seealso marker="logger_disk_log_h">logger_disk_log_h</seealso>.</item>
<item>the built-in formatter,
see <seealso marker="logger_formatter">logger_formatter</seealso>.</item>
<item>built-in filters,
see <seealso marker="logger_filters">logger_filters</seealso>.</item>
</list>
<note>
<p>Since Logger is new in Erlang/OTP 21.0, we do reserve the right
to introduce changes to the Logger API and functionality in
patches following this release. These changes might or might not
be backwards compatible with the initial version.</p>
</note>
</description>
<datatypes>
<datatype>
<name name="filter"/>
<desc>
<p>A filter which can be installed as a handler filter, or as
a primary filter in Logger.</p>
</desc>
</datatype>
<datatype>
<name name="filter_arg"/>
<desc>
<p>The second argument to the filter fun.</p>
</desc>
</datatype>
<datatype>
<name name="filter_id"/>
<desc>
<p>A unique identifier for a filter.</p>
</desc>
</datatype>
<datatype>
<name name="filter_return"/>
<desc>
<p>The return value from the filter fun.</p>
</desc>
</datatype>
<datatype>
<name name="formatter_config"/>
<desc>
<p>Configuration data for the
formatter. See <seealso marker="logger_formatter">
<c>logger_formatter(3)</c></seealso>
for an example of a formatter implementation.</p>
</desc>
</datatype>
<datatype>
<name name="handler_config"/>
<desc>
<p>Handler configuration data for Logger. The following
default values apply:</p>
<list>
<item><c>level => all</c></item>
<item><c>filter_default => log</c></item>
<item><c>filters => []</c></item>
<item><c>formatter => {logger_formatter, DefaultFormatterConfig</c>}</item>
</list>
<p>In addition to these, the following fields are
automatically inserted by Logger, values taken from the
two first parameters
to <seealso marker="#add_handler-3"><c>add_handler/3</c></seealso>:</p>
<list>
<item><c>id => HandlerId</c></item>
<item><c>module => Module</c></item>
</list>
<p>These are read-only and cannot be changed in runtime.</p>
<p>Handler specific configuration data is inserted by the
handler callback itself, in a sub structure associated with
the field named <c>config</c>. See
the <seealso marker="logger_std_h"><c>logger_std_h(3)</c></seealso>
and <seealso marker="logger_disk_log_h"><c>logger_disk_log_h</c></seealso>
manual pages for information about the specifc configuration
for these handlers.</p>
<p>See the <seealso marker="logger_formatter#type-config">
<c>logger_formatter(3)</c></seealso> manual page for
information about the default configuration for this
formatter.</p>
</desc>
</datatype>
<datatype>
<name name="handler_id"/>
<desc>
<p>A unique identifier for a handler instance.</p>
</desc>
</datatype>
<datatype>
<name name="level"/>
<desc>
<p>The severity level for the message to be logged.</p>
</desc>
</datatype>
<datatype>
<name name="log_event"/>
<desc>
<p></p>
</desc>
</datatype>
<datatype>
<name name="metadata"/>
<desc>
<p>Metadata for the log event.</p>
<p>Logger adds the following metadata to each log event:</p>
<list>
<item><c>pid => self()</c></item>
<item><c>gl => group_leader()</c></item>
<item><c>time => erlang:system_time(microsecond)</c></item>
</list>
<p>When a log macro is used, Logger also inserts location
information:</p>
<list>
<item><c>mfa => {?MODULE, ?FUNCTION_NAME, ?FUNCTION_ARITY}</c></item>
<item><c>file => ?FILE</c></item>
<item><c>line => ?LINE</c></item>
</list>
<p>You can add custom metadata, either by specifying a map as
the last parameter to any of the log macros or the API
functions, or by setting process metadata
with <seealso marker="#set_process_metadata-1">
<c>set_process_metadata/1</c></seealso>
or <seealso marker="#update_process_metadata-1">
<c>update_process_metadata/1</c></seealso>.</p>
<p>Logger merges all the metadata maps before forwarding the
log event to the handlers. If the same keys occur, values
from the log call overwrite process metadata, which in turn
overwrite values set by Logger.</p>
<p>The following custom metadata keys have special meaning:</p>
<taglist>
<tag><c>domain</c></tag>
<item>
<p>The value associated with this key is used by filters
for grouping log events originating from, for example,
specific functional
areas. See <seealso marker="logger_filters#domain-2">
<c>logger_filters:domain/2</c></seealso>
for a description of how this field can be used.</p>
</item>
<tag><c>report_cb</c></tag>
<item>
<p>If the log message is specified as
a <seealso marker="#type-report"><c>report()</c></seealso>,
the <c>report_cb</c> key can be associated with a fun
(report callback) that converts the report to a format
string and arguments, or directly to a string. See the
type definition
of <seealso marker="#type-report_cb"><c>report_cb()</c></seealso>,
and
section <seealso marker="logger_chapter#log_message">Log
Message</seealso> in the User's Guide for more
information about report callbacks.</p>
</item>
</taglist>
</desc>
</datatype>
<datatype>
<name name="msg_fun"/>
<desc>
<p></p>
</desc>
</datatype>
<datatype>
<name name="primary_config"/>
<desc>
<p>Primary configuration data for Logger. The following
default values apply:</p>
<list>
<item><c>level => info</c></item>
<item><c>filter_default => log</c></item>
<item><c>filters => []</c></item>
</list>
</desc>
</datatype>
<datatype>
<name name="report"/>
<desc>
<p></p>
</desc>
</datatype>
<datatype>
<name name="report_cb"/>
<desc>
<p>A fun which converts a <seealso marker="#type-report"><c>report()</c>
</seealso> to a format string and arguments, or directly to a string.
See section <seealso marker="logger_chapter#log_message">Log
Message</seealso> in the User's Guide for more
information.</p>
</desc>
</datatype>
<datatype>
<name name="report_cb_config"/>
<desc>
<p></p>
</desc>
</datatype>
<datatype>
<name name="timestamp"/>
<desc>
<p>A timestamp produced
with <seealso marker="erts:erlang#system_time-1">
<c>erlang:system_time(microsecond)</c></seealso>.</p>
</desc>
</datatype>
</datatypes>
<section>
<title>Macros</title>
<p>The following macros are defined in <c>logger.hrl</c>, which
is included in a module with the directive</p>
<code>
-include_lib("kernel/include/logger.hrl").</code>
<list>
<item><c>?LOG_EMERGENCY(StringOrReport[,Metadata])</c></item>
<item><c>?LOG_EMERGENCY(FunOrFormat,Args[,Metadata])</c></item>
<item><c>?LOG_ALERT(StringOrReport[,Metadata])</c></item>
<item><c>?LOG_ALERT(FunOrFormat,Args[,Metadata])</c></item>
<item><c>?LOG_CRITICAL(StringOrReport[,Metadata])</c></item>
<item><c>?LOG_CRITICAL(FunOrFormat,Args[,Metadata])</c></item>
<item><c>?LOG_ERROR(StringOrReport[,Metadata])</c></item>
<item><c>?LOG_ERROR(FunOrFormat,Args[,Metadata])</c></item>
<item><c>?LOG_WARNING(StringOrReport[,Metadata])</c></item>
<item><c>?LOG_WARNING(FunOrFormat,Args[,Metadata])</c></item>
<item><c>?LOG_NOTICE(StringOrReport[,Metadata])</c></item>
<item><c>?LOG_NOTICE(FunOrFormat,Args[,Metadata])</c></item>
<item><c>?LOG_INFO(StringOrReport[,Metadata])</c></item>
<item><c>?LOG_INFO(FunOrFormat,Args[,Metadata])</c></item>
<item><c>?LOG_DEBUG(StringOrReport[,Metadata])</c></item>
<item><c>?LOG_DEBUG(FunOrFormat,Args[,Metadata])</c></item>
<item><c>?LOG(Level,StringOrReport[,Metadata])</c></item>
<item><c>?LOG(Level,FunOrFormat,Args[,Metadata])</c></item>
</list>
<p>All macros expand to a call to Logger, where <c>Level</c> is
taken from the macro name, or from the first argument in the
case of the <c>?LOG</c> macro. Location data is added to the
metadata as described under
the <seealso marker="#type-metadata"><c>metadata()</c></seealso>
type definition.</p>
<p>The call is wrapped in a case statement and will be evaluated
only if <c>Level</c> is equal to or below the configured log
level.</p>
</section>
<section>
<marker id="logging_API"/>
<title>Logging API functions</title>
</section>
<funcs>
<func>
<name>emergency(StringOrReport[,Metadata])</name>
<name>emergency(Format,Args[,Metadata])</name>
<name>emergency(Fun,FunArgs[,Metadata])</name>
<fsummary>Logs the given message as level <c>emergency</c>.</fsummary>
<desc>
<p>Equivalent to
<seealso marker="#log-2"><c>log(emergency,...)</c></seealso>.</p>
</desc>
</func>
<func>
<name>alert(StringOrReport[,Metadata])</name>
<name>alert(Format,Args[,Metadata])</name>
<name>alert(Fun,FunArgs[,Metadata])</name>
<fsummary>Logs the given message as level <c>alert</c>.</fsummary>
<desc>
<p>Equivalent to
<seealso marker="#log-2"><c>log(alert,...)</c></seealso>.</p>
</desc>
</func>
<func>
<name>critical(StringOrReport[,Metadata])</name>
<name>critical(Format,Args[,Metadata])</name>
<name>critical(Fun,FunArgs[,Metadata])</name>
<fsummary>Logs the given message as level <c>critical</c>.</fsummary>
<desc>
<p>Equivalent to
<seealso marker="#log-2"><c>log(critical,...)</c></seealso>.</p>
</desc>
</func>
<func>
<name>error(StringOrReport[,Metadata])</name>
<name>error(Format,Args[,Metadata])</name>
<name>error(Fun,FunArgs[,Metadata])</name>
<fsummary>Logs the given message as level <c>error</c>.</fsummary>
<desc>
<p>Equivalent to
<seealso marker="#log-2"><c>log(error,...)</c></seealso>.</p>
</desc>
</func>
<func>
<name>warning(StringOrReport[,Metadata])</name>
<name>warning(Format,Args[,Metadata])</name>
<name>warning(Fun,FunArgs[,Metadata])</name>
<fsummary>Logs the given message as level <c>warning</c>.</fsummary>
<desc>
<p>Equivalent to
<seealso marker="#log-2"><c>log(warning,...)</c></seealso>.</p>
</desc>
</func>
<func>
<name>notice(StringOrReport[,Metadata])</name>
<name>notice(Format,Args[,Metadata])</name>
<name>notice(Fun,FunArgs[,Metadata])</name>
<fsummary>Logs the given message as level <c>notice</c>.</fsummary>
<desc>
<p>Equivalent to
<seealso marker="#log-2"><c>log(notice,...)</c></seealso>.</p>
</desc>
</func>
<func>
<name>info(StringOrReport[,Metadata])</name>
<name>info(Format,Args[,Metadata])</name>
<name>info(Fun,FunArgs[,Metadata])</name>
<fsummary>Logs the given message as level <c>info</c>.</fsummary>
<desc>
<p>Equivalent to
<seealso marker="#log-2"><c>log(info,...)</c></seealso>.</p>
</desc>
</func>
<func>
<name>debug(StringOrReport[,Metadata])</name>
<name>debug(Format,Args[,Metadata])</name>
<name>debug(Fun,FunArgs[,Metadata])</name>
<fsummary>Logs the given message as level <c>debug</c>.</fsummary>
<desc>
<p>Equivalent to
<seealso marker="#log-2"><c>log(debug,...)</c></seealso>.</p>
</desc>
</func>
<func>
<name name="log" arity="2"/>
<name name="log" arity="3" clause_i="1"/>
<name name="log" arity="3" clause_i="2"/>
<name name="log" arity="3" clause_i="3"/>
<name name="log" arity="4" clause_i="1"/>
<name name="log" arity="4" clause_i="2"/>
<fsummary>Logs the given message.</fsummary>
<type variable="Level"/>
<type variable="StringOrReport" name_i="1"/>
<type variable="Format" name_i="3"/>
<type variable="Args" name_i="3"/>
<type variable="Fun" name_i="4"/>
<type variable="FunArgs" name_i="4"/>
<type variable="Metadata"/>
<desc>
<p>Log the given message.</p>
</desc>
</func>
</funcs>
<section>
<marker id="configuration_API"/>
<title>Configuration API functions</title>
</section>
<funcs>
<func>
<name name="add_handler" arity="3"/>
<fsummary>Add a handler with the given configuration.</fsummary>
<desc>
<p>Add a handler with the given configuration.</p>
<p><c><anno>HandlerId</anno></c> is a unique identifier which
must be used in all subsequent calls referring to this
handler.</p>
</desc>
</func>
<func>
<name name="add_handler_filter" arity="3"/>
<fsummary>Add a filter to the specified handler.</fsummary>
<desc>
<p>Add a filter to the specified handler.</p>
<p>The filter fun is called with the log event as the first
parameter, and the specified <c>filter_args()</c> as the
second parameter.</p>
<p>The return value of the fun specifies if a log event is to
be discarded or forwarded to the handler callback:</p>
<taglist>
<tag><c>log_event()</c></tag>
<item>
<p>The filter <em>passed</em>. The next handler filter, if
any, is applied. If no more filters exist for this
handler, the log event is forwarded to the handler
callback.</p>
</item>
<tag><c>stop</c></tag>
<item>
<p>The filter <em>did not pass</em>, and the log event is
immediately discarded.</p>
</item>
<tag><c>ignore</c></tag>
<item>
<p>The filter has no knowledge of the log event. The next
handler filter, if any, is applied. If no more filters
exist for this handler, the value of
the <c>filter_default</c> configuration parameter for
the handler specifies if the log event shall be
discarded or forwarded to the handler callback.</p>
</item>
</taglist>
<p>See
section <seealso marker="logger_chapter#filters">Filters</seealso>
in the User's Guide for more information about filters.</p>
<p>Some built-in filters exist. These are defined in
<seealso marker="logger_filters"><c>logger_filters</c></seealso>.</p>
</desc>
</func>
<func>
<name name="add_handlers" arity="1" clause_i="1"/>
<fsummary>Set up log handlers from the application's
configuration parameters.</fsummary>
<desc>
<p>Reads the application configuration parameter <c>logger</c> and
calls <c>add_handlers/1</c> with its contents.</p>
</desc>
</func>
<func>
<name name="add_handlers" arity="1" clause_i="2"/>
<fsummary>Setup logger handlers.</fsummary>
<type name="config_handler"/>
<desc>
<p>This function should be used by custom Logger handlers to make
configuration consistent no matter which handler the system uses.
Normal usage is to add a call to <c>logger:add_handlers/1</c>
just after the processes that the handler needs are started,
and pass the application's <c>logger</c> configuration as the argument.
For example:</p>
<code>
-behaviour(application).
start(_, []) ->
case supervisor:start_link({local, my_sup}, my_sup, []) of
{ok, Pid} ->
ok = logger:add_handlers(my_app),
{ok, Pid, []};
Error -> Error
end.</code>
<p>This reads the <c>logger</c> configuration parameter from
the <c>my_app</c> application and starts the configured
handlers. The contents of the configuration use the same
rules as the
<seealso marker="logger_chapter#handler-configuration">logger handler configuration</seealso>.
</p>
<p>If the handler is meant to replace the default handler, the Kernel's
default handler have to be disabled before the new handler is added.
A <c>sys.config</c> file that disables the Kernel handler and adds
a custom handler could look like this:</p>
<code>
[{kernel,
[{logger,
%% Disable the default Kernel handler
[{handler, default, undefined}]}]},
{my_app,
[{logger,
%% Enable this handler as the default
[{handler, default, my_handler, #{}}]}]}].
</code>
</desc>
</func>
<func>
<name name="add_primary_filter" arity="2"/>
<fsummary>Add a primary filter to Logger.</fsummary>
<desc>
<p>Add a primary filter to Logger.</p>
<p>The filter fun is called with the log event as the first
parameter, and the specified <c>filter_args()</c> as the
second parameter.</p>
<p>The return value of the fun specifies if a log event is to
be discarded or forwarded to the handlers:</p>
<taglist>
<tag><c>log_event()</c></tag>
<item>
<p>The filter <em>passed</em>. The next primary filter, if
any, is applied. If no more primary filters exist, the
log event is forwarded to the handler part of Logger,
where handler filters are applied.</p>
</item>
<tag><c>stop</c></tag>
<item>
<p>The filter <em>did not pass</em>, and the log event is
immediately discarded.</p>
</item>
<tag><c>ignore</c></tag>
<item>
<p>The filter has no knowledge of the log event. The next
primary filter, if any, is applied. If no more primary
filters exist, the value of the
primary <c>filter_default</c> configuration parameter
specifies if the log event shall be discarded or
forwarded to the handler part.</p>
</item>
</taglist>
<p>See section <seealso marker="logger_chapter#filters">
Filters</seealso> in the User's Guide for more information
about filters.</p>
<p>Some built-in filters exist. These are defined
in <seealso marker="logger_filters"><c>logger_filters</c></seealso>.</p>
</desc>
</func>
<func>
<name name="get_config" arity="0"/>
<fsummary>Look up the current Logger configuration</fsummary>
<desc>
<p>Look up all current Logger configuration, including primary
and handler configuration, and module level settings.</p>
</desc>
</func>
<func>
<name name="get_handler_config" arity="0"/>
<fsummary>Look up the current configuration for all handlers.</fsummary>
<desc>
<p>Look up the current configuration for all handlers.</p>
</desc>
</func>
<func>
<name name="get_handler_config" arity="1"/>
<fsummary>Look up the current configuration for the given
handler.</fsummary>
<desc>
<p>Look up the current configuration for the given handler.</p>
</desc>
</func>
<func>
<name name="get_handler_ids" arity="0"/>
<fsummary>Look up the identities for all installed handlers.</fsummary>
<desc>
<p>Look up the identities for all installed handlers.</p>
</desc>
</func>
<func>
<name name="get_primary_config" arity="0"/>
<fsummary>Look up the current primary configuration for Logger.</fsummary>
<desc>
<p>Look up the current primary configuration for Logger.</p>
</desc>
</func>
<func>
<name name="get_module_level" arity="0"/>
<fsummary>Look up all current module levels.</fsummary>
<desc>
<p>Look up all current module levels. Returns a list
containing one <c>{Module,Level}</c> element for each module
for which the module level was previously set
with <seealso marker="#set_module_level-2">
<c>set_module_level/2</c></seealso>.</p>
</desc>
</func>
<func>
<name name="get_module_level" arity="1"/>
<fsummary>Look up the current level for the given modules.</fsummary>
<desc>
<p>Look up the current level for the given modules. Returns a
list containing one <c>{Module,Level}</c> element for each
of the given modules for which the module level was
previously set with <seealso marker="#set_module_level-2">
<c>set_module_level/2</c></seealso>.</p>
</desc>
</func>
<func>
<name name="get_process_metadata" arity="0"/>
<fsummary>Retrieve data set with set_process_metadata/1.</fsummary>
<desc>
<p>Retrieve data set
with <seealso marker="#set_process_metadata-1">
<c>set_process_metadata/1</c></seealso> or
<seealso marker="#update_process_metadata-1">
<c>update_process_metadata/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="remove_handler" arity="1"/>
<fsummary>Remove the handler with the specified identity.</fsummary>
<desc>
<p>Remove the handler identified by <c><anno>HandlerId</anno></c>.</p>
</desc>
</func>
<func>
<name name="remove_handler_filter" arity="2"/>
<fsummary>Remove a filter from the specified handler.</fsummary>
<desc>
<p>Remove the filter identified
by <c><anno>FilterId</anno></c> from the handler identified
by <c><anno>HandlerId</anno></c>.</p>
</desc>
</func>
<func>
<name name="remove_primary_filter" arity="1"/>
<fsummary>Remove a primary filter from Logger.</fsummary>
<desc>
<p>Remove the primary filter identified
by <c><anno>FilterId</anno></c> from Logger.</p>
</desc>
</func>
<func>
<name name="set_application_level" arity="2"/>
<fsummary>Set the log level for all modules in the specified application.</fsummary>
<desc>
<p>Set the log level for all the modules of the specified application.</p>
<p>This function is a convenience function that calls
<seealso marker="#set_module_level/2">logger:set_module_level/2</seealso>
for each module associated with an application.</p>
</desc>
</func>
<func>
<name name="set_handler_config" arity="2"/>
<fsummary>Set configuration data for the specified handler.</fsummary>
<desc>
<p>Set configuration data for the specified handler. This
overwrites the current handler configuration.</p>
<p>To modify the existing configuration,
use <seealso marker="#update_handler_config-2">
<c>update_handler_config/2</c></seealso>, or, if a more
complex merge is needed, read the current configuration
with <seealso marker="#get_handler_config-1"><c>get_handler_config/1</c>
</seealso>, then do the merge before writing the new
configuration back with this function.</p>
<p>If a key is removed compared to the current configuration,
and the key is known by Logger, the default value is used. If
it is a custom key, then it is up to the handler
implementation if the value is removed or a default value is
inserted.</p>
</desc>
</func>
<func>
<name name="set_handler_config" arity="3" clause_i="1"/>
<name name="set_handler_config" arity="3" clause_i="2"/>
<name name="set_handler_config" arity="3" clause_i="3"/>
<name name="set_handler_config" arity="3" clause_i="4"/>
<name name="set_handler_config" arity="3" clause_i="5"/>
<fsummary>Add or update configuration data for the specified
handler.</fsummary>
<type variable="HandlerId"/>
<type variable="Level" name_i="1"/>
<type variable="FilterDefault" name_i="2"/>
<type variable="Filters" name_i="3"/>
<type variable="Formatter" name_i="4"/>
<type variable="Config" name_i="5"/>
<type variable="Return"/>
<desc>
<p>Add or update configuration data for the specified
handler. If the given <c><anno>Key</anno></c> already
exists, its associated value will be changed
to the given value. If it does not exist, it will
be added.</p>
<p>If the value is incomplete, which for example can be the
case for the <c>config</c> key, it is up to the handler
implementation how the unspecified parts are set. For all
handlers in the Kernel application, unspecified data for
the <c>config</c> key is set to default values. To update
only specified data, and keep the existing configuration for
the rest, use <seealso marker="#update_handler_config-3">
<c>update_handler_config/3</c></seealso>.</p>
<p>See the definition of
the <seealso marker="#type-handler_config">
<c>handler_config()</c></seealso> type for more
information about the different parameters.</p>
</desc>
</func>
<func>
<name name="set_primary_config" arity="1"/>
<fsummary>Set primary configuration data for Logger.</fsummary>
<desc>
<p>Set primary configuration data for Logger. This
overwrites the current configuration.</p>
<p>To modify the existing configuration,
use <seealso marker="#update_primary_config-1">
<c>update_primary_config/1</c></seealso>, or, if a more
complex merge is needed, read the current configuration
with <seealso marker="#get_primary_config-0"><c>get_primary_config/0</c>
</seealso>, then do the merge before writing the new
configuration back with this function.</p>
<p>If a key is removed compared to the current configuration,
the default value is used.</p>
</desc>
</func>
<func>
<name name="set_primary_config" arity="2" clause_i="1"/>
<name name="set_primary_config" arity="2" clause_i="2"/>
<name name="set_primary_config" arity="2" clause_i="3"/>
<fsummary>Add or update primary configuration data for Logger.</fsummary>
<type variable="Level" name_i="1"/>
<type variable="FilterDefault" name_i="2"/>
<type variable="Filters" name_i="3"/>
<desc>
<p>Add or update primary configuration data for Logger. If the
given <c><anno>Key</anno></c> already exists, its associated
value will be changed to the given value. If it does not
exist, it will be added.</p>
</desc>
</func>
<func>
<name name="set_module_level" arity="2"/>
<fsummary>Set the log level for the specified modules.</fsummary>
<desc>
<p>Set the log level for the specified modules.</p>
<p>The log level for a module overrides the primary log level
of Logger for log events originating from the module in
question. Notice, however, that it does not override the
level configuration for any handler.</p>
<p>For example: Assume that the primary log level for Logger
is <c>info</c>, and there is one handler, <c>h1</c>, with
level <c>info</c> and one handler, <c>h2</c>, with
level <c>debug</c>.</p>
<p>With this configuration, no debug messages will be logged,
since they are all stopped by the primary log level.</p>
<p>If the level for <c>mymodule</c> is now set
to <c>debug</c>, then debug events from this module will be
logged by the handler <c>h2</c>, but not by
handler <c>h1</c>.</p>
<p>Debug events from other modules are still not logged.</p>
<p>To change the primary log level for Logger, use
<seealso marker="#set_primary_config/2">
<c>set_primary_config(level, Level)</c></seealso>.</p>
<p>To change the log level for a handler, use
<seealso marker="#set_handler_config/3">
<c>set_handler_config(HandlerId, level, Level)</c>
</seealso>.</p>
<note>
<p>The originating module for a log event is only detected
if the key <c>mfa</c> exists in the metadata, and is
associated with <c>{Module, Function, Arity}</c>. When log
macros are used, this association is automatically added
to all log events. If an API function is called directly,
without using a macro, the logging client must explicitly
add this information if module levels shall have any
effect.</p>
</note>
</desc>
</func>
<func>
<name name="set_process_metadata" arity="1"/>
<fsummary>Set metadata to use when logging from current process.</fsummary>
<desc>
<p>Set metadata which Logger shall automatically insert in
all log events produced on the current process.</p>
<p>Location data produced by the log macros, and/or metadata
given as argument to the log call (API function or macro),
are merged with the process metadata. If the same keys
occur, values from the metadata argument to the log call
overwrite values from the process metadata, which in turn
overwrite values from the location data.</p>
<p>Subsequent calls to this function overwrites previous data
set. To update existing data instead of overwriting it,
see <seealso marker="#update_process_metadata-1">
<c>update_process_metadata/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="unset_application_level" arity="1"/>
<fsummary>Unset the log level for all modules in the specified application.</fsummary>
<desc>
<p>Unset the log level for all the modules of the specified application.</p>
<p>This function is a convinience function that calls
<seealso marker="#unset_module_level/1">logger:unset_module_level/2</seealso>
for each module associated with an application.</p>
</desc>
</func>
<func>
<name name="unset_module_level" arity="0"/>
<fsummary>Remove module specific log settings for all modules.</fsummary>
<desc>
<p>Remove module specific log settings. After this, the
primary log level is used for all modules.</p>
</desc>
</func>
<func>
<name name="unset_module_level" arity="1"/>
<fsummary>Remove module specific log settings for the given
modules.</fsummary>
<desc>
<p>Remove module specific log settings. After this, the
primary log level is used for the specified modules.</p>
</desc>
</func>
<func>
<name name="unset_process_metadata" arity="0"/>
<fsummary>Delete data set with set_process_metadata/1.</fsummary>
<desc>
<p>Delete data set
with <seealso marker="#set_process_metadata-1">
<c>set_process_metadata/1</c></seealso> or
<seealso marker="#update_process_metadata-1">
<c>update_process_metadata/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="update_formatter_config" arity="2"/>
<fsummary>Update the formatter configuration for the specified handler.</fsummary>
<desc>
<p>Update the formatter configuration for the specified handler.</p>
<p>The new configuration is merged with the existing formatter
configuration.</p>
<p>To overwrite the existing configuration without any merge,
use</p>
<pre>
<seealso marker="#set_handler_config-3">set_handler_config(HandlerId, formatter,
{FormatterModule, FormatterConfig})</seealso>.</pre>
</desc>
</func>
<func>
<name name="update_formatter_config" arity="3"/>
<fsummary>Update the formatter configuration for the specified handler.</fsummary>
<desc>
<p>Update the formatter configuration for the specified handler.</p>
<p>This is equivalent to</p>
<pre>
<seealso marker="#update_formatter_config-2">update_formatter_config(<anno>HandlerId</anno>, #{<anno>Key</anno> => <anno>Value</anno>})</seealso></pre>
</desc>
</func>
<func>
<name name="update_handler_config" arity="2"/>
<fsummary>Update configuration data for the specified handler.</fsummary>
<desc>
<p>Update configuration data for the specified handler. This function
behaves as if it was implemented as follows:</p>
<code type="erl">
{ok, {_, Old}} = logger:get_handler_config(HandlerId),
logger:set_handler_config(HandlerId, maps:merge(Old, Config)).
</code>
<p>To overwrite the existing configuration without any merge,
use <seealso marker="#set_handler_config-2"><c>set_handler_config/2</c>
</seealso>.</p>
</desc>
</func>
<func>
<name name="update_handler_config" arity="3" clause_i="1"/>
<name name="update_handler_config" arity="3" clause_i="2"/>
<name name="update_handler_config" arity="3" clause_i="3"/>
<name name="update_handler_config" arity="3" clause_i="4"/>
<name name="update_handler_config" arity="3" clause_i="5"/>
<fsummary>Add or update configuration data for the specified
handler.</fsummary>
<type variable="HandlerId"/>
<type variable="Level" name_i="1"/>
<type variable="FilterDefault" name_i="2"/>
<type variable="Filters" name_i="3"/>
<type variable="Formatter" name_i="4"/>
<type variable="Config" name_i="5"/>
<type variable="Return"/>
<desc>
<p>Add or update configuration data for the specified
handler. If the given <c><anno>Key</anno></c> already
exists, its associated value will be changed
to the given value. If it does not exist, it will
be added.</p>
<p>If the value is incomplete, which for example can be the
case for the <c>config</c> key, it is up to the handler
implementation how the unspecified parts are set. For all
handlers in the Kernel application, unspecified data for
the <c>config</c> key is not changed. To reset unspecified
data to default values,
use <seealso marker="#set_handler_config-3">
<c>set_handler_config/3</c></seealso>.</p>
<p>See the definition of
the <seealso marker="#type-handler_config">
<c>handler_config()</c></seealso> type for more
information about the different parameters.</p>
</desc>
</func>
<func>
<name name="update_primary_config" arity="1"/>
<fsummary>Update primary configuration data for Logger.</fsummary>
<desc>
<p>Update primary configuration data for Logger. This function
behaves as if it was implemented as follows:</p>
<code type="erl">
Old = logger:get_primary_config(),
logger:set_primary_config(maps:merge(Old, Config)).
</code>
<p>To overwrite the existing configuration without any merge,
use <seealso marker="#set_primary_config-1"><c>set_primary_config/1</c>
</seealso>.</p>
</desc>
</func>
<func>
<name name="update_process_metadata" arity="1"/>
<fsummary>Set or update metadata to use when logging from
current process.</fsummary>
<desc>
<p>Set or update metadata to use when logging from current
process</p>
<p>If process metadata exists for the current process, this
function behaves as if it was implemented as follows:</p>
<code type="erl">
logger:set_process_metadata(maps:merge(logger:get_process_metadata(), Meta)).
</code>
<p>If no process metadata exists, the function behaves as
<seealso marker="#set_process_metadata-1">
<c>set_process_metadata/1</c>
</seealso>.</p>
</desc>
</func>
</funcs>
<section>
<marker id="misc_API"/>
<title>Miscellaneous API functions</title>
</section>
<funcs>
<func>
<name name="compare_levels" arity="2"/>
<fsummary>Compare the severity of two log levels.</fsummary>
<desc>
<p>Compare the severity of two log levels. Returns <c>gt</c>
if <c>Level1</c> is more severe than
<c>Level2</c>, <c>lt</c> if <c>Level1</c> is less severe,
and <c>eq</c> if the levels are equal.</p>
</desc>
</func>
<func>
<name name="format_report" arity="1"/>
<fsummary>Convert a log message on report form to {Format, Args}.</fsummary>
<desc>
<p>Convert a log message on report form to <c>{Format,
Args}</c>. This is the default report callback used
by <seealso marker="logger_formatter">
<c>logger_formatter</c></seealso> when no custom report
callback is found. See
section <seealso marker="logger_chapter#log_message">Log
Message</seealso> in the Kernel User's Guide for
information about report callbacks and valid forms of log
messages.</p>
<p>The function produces lines of <c>Key: Value</c> from
key-value lists. Strings are printed with <c>~ts</c> and
other terms with <c>~tp</c>.</p>
<p>If <c><anno>Report</anno></c> is a map, it is converted to
a key-value list before formatting as such.</p>
</desc>
</func>
</funcs>
<section>
<marker id="handler_callback_functions"/>
<title>Handler Callback Functions</title>
<p>The following functions are to be exported from a handler
callback module.</p>
</section>
<funcs>
<func>
<name>HModule:adding_handler(Config1) -> {ok, Config2} | {error,
Reason}</name>
<fsummary>An instance of this handler is about to be added.</fsummary>
<type>
<v>Config1 = Config2 =
<seealso marker="#type-handler_config">handler_config()</seealso></v>
<v>Reason = term()</v>
</type>
<desc>
<p>This callback function is optional.</p>
<p>The function is called on a temporary process when an new
handler is about to be added. The purpose is to verify the
configuration and initiate all resources needed by the
handler.</p>
<p>The handler identity is associated with the <c>id</c> key
in <c>Config1</c>.</p>
<p>If everything succeeds, the callback function can add
possible default values or internal state values to the
configuration, and return the adjusted map
in <c>{ok,Config2}</c>.</p>
<p>If the configuration is faulty, or if the initiation fails,
the callback function must return <c>{error,Reason}</c>.</p>
</desc>
</func>
<func>
<name>HModule:changing_config(SetOrUpdate, OldConfig, NewConfig) -> {ok, Config} | {error, Reason}</name>
<fsummary>The configuration for this handler is about to change.</fsummary>
<type>
<v>SetOrUpdate = set | update</v>
<v>OldConfig = NewConfig = Config =
<seealso marker="#type-handler_config">handler_config()</seealso></v>
<v>Reason = term()</v>
</type>
<desc>
<p>This callback function is optional.</p>
<p>The function is called on a temporary process when the
configuration for a handler is about to change. The purpose
is to verify and act on the new configuration.</p>
<p><c>OldConfig</c> is the existing configuration
and <c>NewConfig</c> is the new configuration.</p>
<p>The handler identity is associated with the <c>id</c> key
in <c>OldConfig</c>.</p>
<p><c>SetOrUpdate</c> has the value <c>set</c> if the
configuration change originates from a call to
<seealso marker="#set_handler_config-2">
<c>set_handler_config/2,3</c></seealso>, and <c>update</c>
if it originates from <seealso marker="#update_handler_config-2">
<c>update_handler_config/2,3</c></seealso>. The handler can
use this parameteter to decide how to update the value of
the <c>config</c> field, that is, the handler specific
configuration data. Typically, if <c>SetOrUpdate</c>
equals <c>set</c>, values that are not specified must be
given their default values. If <c>SetOrUpdate</c>
equals <c>update</c>, the values found in <c>OldConfig</c>
must be used instead.</p>
<p>If everything succeeds, the callback function must return a
possibly adjusted configuration in <c>{ok,Config}</c>.</p>
<p>If the configuration is faulty, the callback function must
return <c>{error,Reason}</c>.</p>
</desc>
</func>
<func>
<name>HModule:filter_config(Config) -> FilteredConfig</name>
<fsummary>Remove internal data from configuration.</fsummary>
<type>
<v>Config = FilteredConfig =
<seealso marker="#type-handler_config">handler_config()</seealso></v>
</type>
<desc>
<p>This callback function is optional.</p>
<p>The function is called when one of the Logger API functions
for fetching the handler configuration is called, for
example
<seealso marker="#get_handler_config-1">
<c>logger:get_handler_config/1</c></seealso>.</p>
<p>It allows the handler to remove internal data fields from
its configuration data before it is returned to the
caller.</p>
</desc>
</func>
<func>
<name>HModule:log(LogEvent, Config) -> void()</name>
<fsummary>Log the given log event.</fsummary>
<type>
<v>LogEvent =
<seealso marker="#type-log_event">log_event()</seealso></v>
<v>Config =
<seealso marker="#type-handler_config">handler_config()</seealso></v>
</type>
<desc>
<p>This callback function is mandatory.</p>
<p>The function is called when all primary filters and all
handler filters for the handler in question have passed for
the given log event. It is called on the client process, that
is, the process that issued the log event.</p>
<p>The handler identity is associated with the <c>id</c> key
in <c>Config</c>.</p>
<p>The handler must log the event.</p>
<p>The return value from this function is ignored by
Logger.</p>
</desc>
</func>
<func>
<name>HModule:removing_handler(Config) -> ok</name>
<fsummary>The given handler is about to be removed.</fsummary>
<type>
<v>Config =
<seealso marker="#type-handler_config">handler_config()</seealso></v>
</type>
<desc>
<p>This callback function is optional.</p>
<p>The function is called on a temporary process when a
handler is about to be removed. The purpose is to release
all resources used by the handler.</p>
<p>The handler identity is associated with the <c>id</c> key
in <c>Config</c>.</p>
<p>The return value is ignored by Logger.</p>
</desc>
</func>
</funcs>
<section>
<marker id="formatter_callback_functions"/>
<title>Formatter Callback Functions</title>
<p>The following functions are to be exported from a formatter
callback module.</p>
</section>
<funcs>
<func>
<name>FModule:check_config(FConfig) -> ok | {error, Reason}</name>
<fsummary>Validate the given formatter configuration.</fsummary>
<type>
<v>FConfig =
<seealso marker="#type-formatter_config">formatter_config()</seealso></v>
<v>Reason = term()</v>
</type>
<desc>
<p>This callback function is optional.</p>
<p>The function is called by a Logger when formatter
configuration is set or modified. The formatter must
validate the given configuration and return <c>ok</c> if it
is correct, and <c>{error,Reason}</c> if it is faulty.</p>
<p>The following Logger API functions can trigger this callback:</p>
<list>
<item><seealso marker="logger#add_handler-3">
<c>logger:add_handler/3</c></seealso></item>
<item><seealso marker="logger#set_handler_config-2">
<c>logger:set_handler_config/2,3</c></seealso></item>
<item><seealso marker="logger#update_handler_config-2">
<c>logger:update_handler_config/2,3</c></seealso></item>
<item><seealso marker="logger#update_formatter_config-2">
<c>logger:update_formatter_config/2</c></seealso></item>
</list>
<p>See <seealso marker="logger_formatter">
<c>logger_formatter(3)</c></seealso>
for an example implementation. <c>logger_formatter</c> is the
default formatter used by Logger.</p>
</desc>
</func>
<func>
<name>FModule:format(LogEvent, FConfig) -> FormattedLogEntry</name>
<fsummary>Format the given log event.</fsummary>
<type>
<v>LogEvent =
<seealso marker="#type-log_event">log_event()</seealso></v>
<v>FConfig =
<seealso marker="#type-formatter_config">formatter_config()</seealso></v>
<v>FormattedLogEntry =
<seealso marker="unicode#type-chardata">unicode:chardata()</seealso></v>
</type>
<desc>
<p>This callback function is mandatory.</p>
<p>The function can be called by a log handler to convert a
log event term to a printable string. The returned value
can, for example, be printed as a log entry to the console
or a file using <seealso marker="stdlib:io#put_chars-1">
<c>io:put_chars/1,2</c></seealso>.</p>
<p>See <seealso marker="logger_formatter">
<c>logger_formatter(3)</c></seealso>
for an example implementation. <c>logger_formatter</c> is the
default formatter used by Logger.</p>
</desc>
</func>
</funcs>
<section>
<title>See Also</title>
<p>
<seealso marker="config"><c>config(4)</c></seealso>,
<seealso marker="erts:erlang"><c>erlang(3)</c></seealso>,
<seealso marker="stdlib:io"><c>io(3)</c></seealso>,
<seealso marker="logger_disk_log_h"><c>logger_disk_log_h(3)</c></seealso>,
<seealso marker="logger_filters"><c>logger_filters(3)</c></seealso>,
<seealso marker="logger_formatter"><c>logger_formatter(3)</c></seealso>,
<seealso marker="logger_std_h"><c>logger_std_h(3)</c></seealso>,
<seealso marker="stdlib:unicode"><c>unicode(3)</c></seealso>
</p>
</section>
</erlref>
|