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       clfmerge - merge Common-Log Format web logs based on time-stamps


       clfmerge [--help | -h] [-b size] [-d] [file names]


       The  clfmerge program is designed to avoid using sort to merge multiple
       web log files.  Web logs for big sites consist of multiple files in the
       >100M  size  range from a number of machines.  For such files it is not
       practical to use a program such as gnusort to merge the  files  because
       the  data  is  not  always  entirely  in  order (so the merge option of
       gnusort doesn’t work so well), but it is not in random order (so  doing
       a  complete  sort would be a waste).  Also the date field that is being
       sorted on is not particularly easy to specify for gnusort (I have  seen
       it done but it was messy).

       This  program is designed to simply and quickly sort multiple large log
       files with no need for temporary storage space or overly large  buffers
       in memory (the memory footprint is generally only a few megs).


       It  will take a number (from 0 to n) of file-names on the command line,
       it will open them for reading and read CLF format  web  log  data  from
       them all.  Lines which don’t appear to be in CLF format (NB they aren’t
       parsed fully, only minimal parsing to determine the date is  performed)
       will be rejected and displayed on standard-error.

       If  zero  files are specified then there will be no error, it will just
       silently output nothing, this is for scripts which use the find command
       to  find log files and which can’t be counted on to find any log files,
       it saves doing an extra check in your shell scripts.

       If one file is specified then the data will be read into  a  1000  line
       buffer  and  it  will  be  removed  from  the  buffer (and displayed on
       standard output) in date order.  This is to  handle  the  case  of  web
       servers which date entries on the connection time but write them to the
       log at completion time and thus generate log files that aren’t in order
       (Netscape  web  server  does  this  -  I haven’t checked what other web
       servers do).

       If more than one file is specified then a line will be read  from  each
       file, the file that had the earliest time stamp will be read from until
       it returns a time stamp later than one of the other  files.   Then  the
       file with the earlier time stamp will be read.  With multiple files the
       buffer size is 1000 lines or 100 * the number of  files  (whichever  is
       larger).   When  the buffer becomes full the first line will be removed
       and displayed on standard output.


       -b buffer-size
              Specify the buffer-size to use, if 0 is specified then it  means
              to disable the sliding-window sorting of the data which improves
              the speed.

       -d     Set domain-name mangling to on.   This  means  that  if  a  line
              starts with as the name of the site that was requested then that
              would be removed from the start of the line and the GET /  would
              be  changed to GET which allows programs
              like Webalizer to produce good graphs for large  hosting  sites.
              Also it will make the domain name in lower case.


       0 No errors

       1 Bad parameters

       2 Can’t open one of the specified files

       3 Can’t write to output


       This  program,  its manual page, and the Debian package were written by
       Russell Coker <>.