linux - Extract value from .gz log files in unix -

i'm trying extract specific value (e.g useragent in case) bunch of .gz log files compressed log files. format of each log statement in these log files looks :

2013-06-20;02:00:02.503 [664492205@qtp-446095113-8883]-activity [response@12293 appid=testapp useragent=bundledevicefamily/iphone,ipad (ipad; ipad2,5; ipad2,5; iphone os 6.1.3) exec_tm=123  flow=response tokn_tm=0 gw_tm=2314.529 http.status=200 id=029dde45-802c-462a-902b-138bc5490fba offeringid=ipad httpurl= test.com aud_tm=0 ipaddress=10.10.10.10 ]\  2013-06-20;02:00:02.504 [664492205@qtp-446095113-8883]-activity [response@12293 appid=testapp useragent=fnetwork/609.1.4 darwin/13.0.0 id=029dde45-802c-462a-902b-138bc5490fba exec_tm=123  flow=response tokn_tm=0 gw_tm=2314.529 http.status=200  offeringid=ipad httpurl= test.com aud_tm=0 ipaddress=10.10.10.10 ] 

in case, want extract useragent field , display result either in 1 of below formats:

useragent=bundledevicefamily/iphone,ipad (ipad; ipad2,5; ipad2,5; iphone os 6.1.3) useragent=fnetwork/609.1.4 darwin/13.0.0 

and on..

or print values such :

bundledevicefamily/iphone,ipad (ipad; ipad2,5; ipad2,5; iphone os 6.1.3) fnetwork/609.1.4 darwin/13.0.0 

edit : add more info, these space seperated fields such key1=value1 key2=value2 appear in order

appreciate help. thanks!

since mentioned key=value pairs can appear in order, here 1 way of doing awk.

zcat input.gz | awk -f= ' {   for(i=1;i<=nf;i++) {     if($i~/useragent/) {        sub(/[^ ]+$/,"",$(i+1))       print "useragent="$(i+1)      }   } }'