BloombergLP::ball::FileObserver::setFileLogFormat

Set the format specifications for log records written to the log file to logFileFormat. See {Log Record Formatting} for details on the syntax of format specifications. Return zero if the format is valid and the corresponding formatter has been set. Otherwise, if the format is invalid, return a non‐zero value and do not change the formatter. Note that default format is in effect following construction until a format‐setting method is called ("n%d %p:%t %s %f:%l %c %m %un" for both file and stdout logging).