Group hostname(?<hostname>\S+?) \S+?any non-whitespace character, repeated at least once
?repeats the group contents below at most once:
\sany whitespace character
:the literal : (5810 / 728 / 3A16)
?repeats the group contents below at most once:
\sany whitespace character
\%the literal % (3710 / 458 / 2516)
ASAthe literal text ASA (case insensitive) .+?any character (except for line terminators), repeated at least once
\sany whitespace character
forthe literal text for (case insensitive) \sany whitespace character
fromthe literal text from (case insensitive) .+?any character (except for line terminators), repeated at least once
?repeats the group contents below at most once:
:the literal : (5810 / 728 / 3A16)
=the literal = (6110 / 758 / 3D16)
\ban ASCII word boundary
Group srcip(?<srcip>(?:[0-9]{1,3}\.){3}[0-9]{1,3}) Non-Capturing Group(?:[0-9]{1,3}\.){3} {3}repeats the group contents below exactly 3 times:
Character Class[0-9]{1,3} {1,3}matches between 1 and 3 characters from the set below:
0-9one character from 0 (4810) to 9 (5710)
\.the literal . (4610 / 568 / 2E16)
Character Class[0-9]{1,3} {1,3}matches between 1 and 3 characters from the set below:
0-9one character from 0 (4810) to 9 (5710)
?repeats the group contents below at most once:
\/the literal / (4710 / 578 / 2F16)
:the literal : (5810 / 728 / 3A16)
Group 8((?<srcport>\d+))? ?repeats the group contents below at most once:
Group srcport(?<srcport>\d+) \d+a digit, repeated at least once
.+?any character (except for line terminators), repeated at least once
i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string