[#FB_LOGF]
= FB&lowbar;LOGF
:mrdocs:

Log a message to the specified logger, using a fmt&colon;&colon;format() string&period;

== Synopsis

Declared in `&lt;folly&sol;logging&sol;Logger&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
#define FB&lowbar;LOGF(logger, level, fmt, arg1, ...)

----

== Description

The arguments will be processed using fmt&colon;&colon;format()&period; The format syntax is similar to Python format strings&period;

This macro avoids evaluating the log arguments unless the log level check succeeds&period;

Beware that the logger argument is evaluated twice, so this argument should be an expression with no side&hyphen;effects&period;

== Parameters

[cols="1,4"]
|===
| Name| Description
| *logger*
| The logger identifying the log category&period;
| *level*
| The unqualified `folly&colon;&colon;LogLevel` name&period;
| *fmt*
| The `fmt&colon;&colon;format` format string&period;
| *arg1*
| The first format argument&period;
|===


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