MySQL database server generates binary log files for every transaction to the databases, provided administrator does not disable or comment out the “log-bin” parameter in my.cny configuration file. The binary log files are written in binary format. Although the binary logs, or also known as logbin are mainly used for Mysql database replication purpose, sometimes you may need to examine or read the contents of binary logs in text format, where the mysqlbinlog utility will come in handy.
Binary log file, which normally has name with the format host_name-bin.xxxxxx and will be store in your data directory, could not be opened and read straight away as it’s in unreadable binary format. To read the binary logs in text format, we can make use of mysqlbinlog command, which also able to readrelay log files written by a slave server in a replication setup. Relay logs have the same format as binary log files.
To use mysqlbinlog utility is simple, simply use the following command syntax to invoke mysqlbinlog after login in as root (else you have to specify user name and password) to shell via SSH:
mysqlbinlog [options] log_file …
So to read and display the contents of the binary log file named binlog.000001, use this command:
The binary log files and its data are likely to be very huge, thus making it almost impossible to read anything on screen. However, you can pipe the output of mysqlbinlog into a file which can be open up for later browsing in text editor, by using the following command:
mysqlbinlog binlog.000001 > filename.txt
To reduce the amount of data retrieved from binary logs, there are several options that can be used to limit the data that is been returned. Among the useful ones are listed below:
Start reading the binary log at the first event having a timestamp equal to or later than the datetime argument. The datetime value is relative to the local time zone on the machine where you run mysqlbinlog. The value should be in a format accepted for the DATETIME or TIMESTAMP data types. For example:
mysqlbinlog –start-datetime=”2005-12-25 11:25:56″ binlog.000001
Stop reading the binary log at the first event having a timestamp equal or posterior to the datetime argument. This option is useful for point-in-time recovery. See the description of the –start-datetime option for information about the datetime value.
Start reading the binary log at the first event having a position equal to the N argument. This option applies to the first log file named on the command line.
Stop reading the binary log at the first event having a position equal or greater than the N argument. This option applies to the last log file named on the command line.