아파치 로그포맷에 PID 값을 넣어주고 싶으면 아래에 보듯이
$P 를 추가 시켜 주면 된다.

아래는 자세한 로그 포맷들...........

%...b:          Bytes sent, excluding HTTP headers.
%...f:          Filename
%...{FOOBAR}e:  The contents of the environment variable FOOBAR
%...h:          Remote host
%...{Foobar}i:  The contents of Foobar: header line(s) in the request
               sent to the server.
%...l:          Remote logname (from identd, if supplied)
%...{Foobar}n:  The contents of note "Foobar" from another module.
%...{Foobar}o:  The contents of Foobar: header line(s) in the reply.
%...p:          The port the request was served to
%...P:          The process ID of the child that serviced the request.
%...r:          First line of request
%...s:          Status.  For requests that got internally redirected, 
this
               is status of the *original* request --- %...>s for the 
last.
%...t:          Time, in common log format time format
%...{format}t:  The time, in the form given by format, which should
               be in strftime(3) format.
%...T:          The time taken to serve the request, in seconds.
%...u:          Remote user (from auth; may be bogus if return status () 
is 401)
%...U:          The URL path requested.
%...v:          The name of the server (i.e. which virtual host?)