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Rebex CONVLOG v1.6

RCONVLOG (Rebex Internet Log Converter) converts web server log files from W3C log format into NCSA log format. It can be very useful especially when using a log analyzer which does not support a native IIS format or a W3C Extended format (e.g. excellent Webalizer -

IIS is shipped with a similar program called convlog, which is able to convert web server log files into NCSA Common Log format. However, using Microsoft convlog causes some problems: Original convlog does not convert user agents (browsers) and referrers. It also ignores all uploads, which makes generating statistics from FTP log files impossible.

RCONVLOG deals with all those difficulties - it is nearly identical to original convlog, but it does work as expected. In most cases, RCONVLOG can be used as an out-of-the-box replacement or a bugfix release of the original ;-)

Advantages of RCONVLOG:

  • supports browsers
  • supports referrers
  • upload, download or both can be choosen for conversion
  • a powerful and efficient DNS lookup and a caching mechanism
  • Linux and FreeBSD ports are also available

Other features of RCONVLOG:

  • converts web server log files from W3C Log Format to NCSA Common Log format
  • supports browser agents
  • supports referrers
  • supports both upload and download
  • a powerful and efficient DNS lookup and a caching mechanism
  • a call format is compatible with Microsoft convlog.

Note: Currently, RCONVLOG only understands W3C Extended format. If you need to process MS Internet Standard Log File Format or NCSA Common Log format, mail us - we will add it upon first request.


FREEWARE. Can be downloaded from



  • Windows
  • Cygwin (Unix environment for Windows -
  • Linux (tested on RedHat 7 and Debian 3, but should compile with other distributions as well)
  • FreeBSD (tested on 4.6.2)


  • Microsoft Visual C++
  • GCC

Thanks to Christophe Paquin ( for initial unix port.
Thanks to for initial cookies support.


rconvlog [options] LogFile1 [LogFile2] [LogFile3] ...


File(s) is W3C format to be converted - may contain wildcards such
as ? and *.


Directory where logfiles in NCSA Combined format will be created.
Default is current directory. Created files will have filename
of the original ones + extension ".ncsa" (or "ncsa.dns" for -d option).


Use this file as hostname cache. If filename without path is specified,
path of RCONVLOG.exe (use .\filename to specify
file in current directory). Cache saves time when executing RCONVLOG
multiple - resolved hostnames can be reused.

-t <ncsa[:GMTOffset]>

Specifies GTM Offset to use in NCSA logfile. Default is ncsa:+0000.

-d Convert IP addresses to domain names if possible.

-w Overwrite existing NCSA log files (default is append).


How to log bytes sent:
0 = be compatible with convlog (default)
1 = log bytes sent from server to client only (download)
2 = log bytes sent from client to server only (upload)
3 = log sum of bytes sent both ways (upload and download)


Ignore records older than specified datetime (eg. -n 2001-12-20T00:00:00)

-u Turn on cookie support

Urchin ( log analysis feature called UTM
(urchin tracking module) requires IIS to turn on the cs(Cookie) field.
This option appends the cookie field to the NCSA-format log.
Sample IIS log header from Urchin UTM-enabled site:

#Fields: date time c-ip cs-username s-ip s-port cs-method cs-uri-stem cs-uri-query
sc-status cs(User-Agent) cs(Cookie) cs(Referer)

-h H Ignore records older than H hours (eg. -h 164)

Version history

v1.0 - 2001-05-17 - initial version
v1.1 - 2001-10-30 - added support for ignoring old records (-n and -h arguments)
v1.2 - 2002-01-06 - fixed a simple bug which caused rconvlog to ignore january records
v1.3 - 2002-12-17 - many enhancements and smaller bug fixes
                  - rconvlog now compiles on windows and unix
                  - changed the way of progress reporting
v1.4 - 2004-07-08 - fixed a bug that caused fields to be ignored if their number
                    exceeded 21
v1.5 - 2005-04-29 - fixed a bug that caused negative offsets of -t argument to fail
                  - output directory specified by -o and input files specified
                    by LogFile arguments are now combined to an output path
v1.6 - 2009-01-22 - added switch to append cookie field to NCSA-format log

Copyright (c) 2001-2009 Rebex
Written by Lukas Pokorny (


Multiplatform 'convlog' replacement




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