import re
s='''178.197.215.191:46582 - - [25/Sep/2023:17:02:59 +0000] "GET /web/login HTTP/1.1" 502 2200 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/117.0" "178.197.215.191" "bluestar-proxy.jcloud.ik-server.com" sn="bluestar-proxy.jcloud.ik-server.com" rt=4.830 ua="10.100.24.98:8069 : 10.100.26.168:5000" us="502 : 200" ut="3.006 : 1.823" ul="0 : 2200" cs=-
178.197.215.191:46582 - - [25/Sep/2023:17:03:00 +0000] "GET /favicon.ico HTTP/1.1" 200 15086 "http://b...content-available-to-author-only...r.com/web/login" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/117.0" "178.197.215.191" "bluestar-proxy.jcloud.ik-server.com" sn="bluestar-proxy.jcloud.ik-server.com" rt=0.000 ua="-" us="-" ut="-" ul="-" cs=-
'''
m = re.search(r'(?s:.*)^.*\[(.*)\]', s, re.M)
if m:
print(m.groups(1))
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