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<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>2017</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_formatter</title>
<prepared></prepared>
<responsible></responsible>
<docno></docno>
<approved></approved>
<checked></checked>
<date></date>
<rev>A</rev>
<file>logger_formatter.xml</file>
</header>
<module>logger_formatter</module>
<modulesummary>Default formatter for the Logger application.</modulesummary>
<description>
<p>Default formatter for the Logger application.</p>
</description>
<section>
<title>Configuration</title>
<p>The following configuration parameters can be set
for <c>logger_formatter</c>:</p>
<taglist>
<tag><c>single_line = boolean()</c></tag>
<item>
<p>If set to <c>true</c>, all newlines in the message are
replaced with <c>", "</c>, and whitespaces following
directly after newlines are removed. Note that newlines
added by the formatter template are not replaced.</p>
<p>Default is <c>true</c>.</p>
</item>
<tag><c>legacy_header = boolen()</c></tag>
<item>
<p>If set to <c>true</c> a header field is added to
logger_formatter's part of <c>Metadata</c>. The value of
this field is a string similar to the header created by the
old <c>error_logger</c> event handlers. It can be included
in the log event by adding the
tuple <c>{logger_formatter,header}</c> to the
template. See <seealso marker="#default_templates">Default
Templates</seealso> for more information</p>
<p>Default is <c>false</c>.</p>
</item>
<tag><c>report_cb = fun((logger:report()) -> {io:format(),[term()]})</c></tag>
<item>
<p>A function with arity 1,
returning <c>{Format,Args}</c>. This function will replace
any <c>report_cb</c> found in metadata.</p>
</item>
<tag><c>depth = pos_integer() | unlimited</c></tag>
<item>
<p>A positive integer representing the maximum depth to
which terms shall be printed by this formatter. Format
strings passed to this formatter are rewritten. The format
controls ~p and ~w are replaced with ~P and ~W,
respectively, and the value is used as the depth
parameter. For details, see
<seealso marker="stdlib:io#format-2">io:format/2,3</seealso>
in STDLIB.</p>
<p>Default is <c>unlimited</c>.</p>
</item>
<tag><c>chars_limit = pos_integer() | unlimited</c></tag>
<item>
<p>A positive integer representing the value of the option
with the same name to be used when calling
<seealso marker="stdlib:io_lib#format-3">io_lib:format/3</seealso>.
This value limits the total number of characters printed
for each log event. Note that this is a soft limit. For a
hard truncation limit, see option <c>max_size</c>.</p>
<p>Default is <c>unlimited</c>.</p>
</item>
<tag><c>max_size = pos_integer() | unlimited</c></tag>
<item>
<p>A positive integer representing the absolute maximum size
a string returned from this formatter can have. If the
formatted string is longer, after possibly being limited
by <c>depth</c> and/or <c>chars_limit</c>, it will be
truncated.</p>
<p>Default is <c>unlimited</c>.</p>
</item>
<tag><c>template = </c><seealso marker="#type-template"><c>template()</c></seealso></tag>
<item>
<p>The template is a list of atoms, tuples and strings. The
atoms <c>level</c> or <c>msg</c>, are treated as
placeholders for the severity level and the log message,
repectively. Other atoms or tuples are interpreted as
placeholders for metadata, where atoms are expected to
match top level keys, and tuples represent paths to sub
keys in a nested map. For example the
tuple <c>{key1,key2}</c> will be replaced by the value of
the <c>key2</c> field in the nested map below. The
atom <c>key1</c> on its own would be replaced by the
complete value of the <c>key1</c> field. The values are
converted to strings.</p>
<code>
#{key1=>#{key2=>my_value,
...}
...}</code>
<p>Strings are printed literally.</p>
<p>The default template differs depending on the values
of <c>legacy_header</c>
and <c>single_line</c>. See <seealso marker="#default_templates">Default
Templates</seealso> for more information</p>
</item>
<tag><c>utc = boolean()</c></tag>
<item>
<p>If set to <c>true</c>, all dates are displayed in Universal
Coordinated Time. Default is <c>false</c>.</p>
</item>
</taglist>
</section>
<section>
<marker id="default_templates"/>
<title>Default templates</title>
<p>The default template when <c>legacy_header=true</c> is</p>
<code>[{logger_formatter,header},"\n",msg,"\n"]</code>
<p>which will cause log entries like this:</p>
<code>=ERROR REPORT==== 29-Dec-2017::13:30:51.245123 ===
process: <0.74.0>
exit_reason: "Something went wrong"</code>
<p>Note that all eight levels might occur here, not
only <c>ERROR</c>, <c>WARNING</c> or <c>INFO</c>. And also that
micro seconds are added at the end of the timestamp.</p>
<p>The default template when <c>single_line=true</c> is</p>
<code>[time," ",level,": ",msg,"\n"]</code>
<p>which will cause log entries like this:</p>
<code>2017-12-29 13:31:49.640317 error: process: <0.74.0>, exit_reason: "Something went wrong"</code>
<p>The default template when both <c>legacy_header</c> and
<c>single_line</c> are set to false is:</p>
<code>[time," ",level,":\n",msg,"\n"]</code>
<p>which will cause log entries like this:</p>
<code>2017-12-29 13:32:25.191925 error:
process: <0.74.0>
exit_reason: "Something went wrong"</code>
</section>
<datatypes>
<datatype>
<name name="template"/>
<desc>
</desc>
</datatype>
</datatypes>
<funcs>
<func>
<name name="format" arity="2"/>
<fsummary>Formats the given message.</fsummary>
<desc>
<p>This the callback function to be called from handlers. It
formats the given messages.</p>
</desc>
</func>
</funcs>
</erlref>
