Formatters

The PatternFormatter specifies the layout of log records in the final output.

Each LoggerImpl object has a PatternFormatter object. This means that each Logger can be customised to output in a different format.

Customising the format output only be done during the creation of the logger via the PatternFormatterOptions

If no custom format is set each newly created Sink uses the same formatting as the default logger.

The format output can be customised by providing a string of certain attributes.

Name	Format	Description
time	%(time)	Human-readable timestamp when the log statement was issued
file_name	%(file_name)	Filename only, excluding the full path
full_path	%(full_path)	Full path of the source file where the logging call was issued
caller_function	%(caller_function)	Name of function containing the logging call
log_level	%(log_level)	Log level description (‘TRACEL3’, ‘TRACEL2’, ‘TRACEL1’, ‘DEBUG’, ‘INFO’, ‘WARNING’, ‘ERROR’, ‘CRITICAL’, ‘BACKTRACE’)
log_level_short_code	%(log_level_short_code)	Abbreviated log level (‘T3’, ‘T2’, ‘T1’, ‘D’, ‘I’, ‘W’, ‘E’, ‘C’, ‘BT’)
line_number	%(line_number)	Source line number where the logging call was issued
logger	%(logger)	Name of the logger
message	%(message)	The log message
thread_id	%(thread_id)	Thread ID, if available
thread_name	%(thread_name)	Thread name, if set. The name of the thread must be set prior to issuing any log statement on that thread
process_id	%(process_id)	Process ID
source_location	%(source_location)	Full source file path and line number as a single string
short_source_location	%(short_source_location)	Filename and line number as a single string formatted as filename:line, excluding the full file path
tags	%(tags)	Additional custom tags appended to the message when _TAGS macros are used
named_args	%(named_args)	Key-value pairs appended to the message. Only applicable with for a named args format string; remains empty otherwise

Customising the timestamp

The timestamp is customisable by :

• Format. Same format specifiers as strftime(...) format without the additional .Qms .Qus .Qns arguments.

• Local timezone or GMT timezone. Local timezone is used by default.

• Fractional second precision. Using the additional fractional second specifiers in the timestamp format string.

Specifier	Description
%Qms	Milliseconds
%Qus	Microseconds
%Qns	Nanoseconds

By default "%H:%M:%S.%Qns" is used.

Note

MinGW does not support all strftime(...) format specifiers and you might get a bad alloc if the format specifier is not supported

Customizing Log Message Formats

quill::Logger* logger =
  quill::Frontend::create_or_get_logger("root", std::move(sink),
                                        quill::PatternFormatterOptions { "%(time) [%(thread_id)] %(short_source_location:<28) "
                                        "LOG_%(log_level:<9) %(logger:<12) %(message)",
                                        "%H:%M:%S.%Qns", quill::Timezone::GmtTime });