[#BloombergLP-bsls-Log-LogMessageHandler-05]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bsls.adoc[bsls]::xref:BloombergLP/bsls/Log.adoc[Log]::LogMessageHandler
:relfileprefix: ../../../
:mrdocs:

The `LogMessageHandler` `typedef` represents a type of function that handles log messages in an unspecified way (e&period;g&period;, by writing the log message to an output stream or to a file)&period; Because they can be called concurrently from multiple threads, log message handlers must be thread&hyphen;safe&period; While installed, handlers must exhibit only defined behavior if the specified `file` is a null&hyphen;terminated string, the specified `line` is not negative, and the specified `message` is a null&hyphen;terminated string&period;

== Synopsis

Declared in `&lt;bsls&lowbar;log&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
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typedef void(* LogMessageHandler)(xref:BloombergLP/bsls/LogSeverity/Enum.adoc[bsls::LogSeverity::Enum], char const*, int, char const*);
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