part 4 apache conditional handling

conditional handling features:

A) make decisions based on current conditions:
 1) modules available
 2) remote HOST
 3) browser type - useragent(http header request)

B) <IfDefine> parameter - directives to be processed at server startup
C) <IfModule> - directive to be processed based on module existence. Eg mod_ssl
D) <IfVersion> - directive processed based on version of apache
E) SetEnvIf[NoCase] -sets environmental VAR (variable) based on :
   HTTP Request Header : i,e User-Agent, Referer , Accept-Language
   Remote_(Addr|Host) server_addr, Request_(method|Protocol), Request_URI
   Predefined Environmental VARs using : SetEnvIf[NoCase]
  
Task:

 Explore <IfModule>

 apachectl -D DUMP_MODULES 
 or
 apache2ctl -M | grep -E "(static|shared)" | wc -l

 cd /etc/apache2 && grep -R -i 'ifmodule' *   --searches for ifmodule

 inside the <VirutalHost>
 <VirtualHost>
 ..
 SetEnvIf Referer "site1.linuxcbt.internal" site1_referrer
 CustomLog /var/log/apache2/site2.site1_referral.access.log combined env=site1_referrer
 </VirtualHost>