Usage:

mgstat -l mod_gzip_log -d output_dir

mod_gzip_log - full path to a log file produced by mod_gzip.
output_dir - directory where html, gif and history files are stored.

Below directives (in httpd.conf) produces desired log file:

LogFormat "%h %l %u %t \"%V %r\" %>s %b mod_gzip: %{mod_gzip_result}n In:%{mod_gzip_input_size}n Out:%{mod_gzip_output_size}n:%{mod_gzip_compression_ratio}npct." common_with_mod_gzip_info2
CustomLog /var/log/httpd/mod_gzip_log common_with_mod_gzip_info2

