regex

special chars

CHARACTERCOMMENTS

?:

non capturing group

?=

positive look ahead

?!

negative look ahead

?<=

positive look behind

?<!

negative look behind

samples

get URL

$ echo http://www.baidu.com | awk '{for(i=1;i<=NF;i++){if($i~/^(http|ftp):\/\//)print $i}}'
http://www.baidu.com

references:

matches if exits

[!NOTE|label:samples:]

✔️   keyword.baz.com
✔️   string-keyword.baz.com
✔️   keyword-staging.bar.com
✔️   keyword-staging.foo.com
^.*keyword(?:-staging)?\.[^\]+\.com

[!NOTE|label:samples:]

❌ /etc/kubernetes/config.backup/config.backup.20220303/admin.conf
✔️  /etc/kubernetes/pki/admin.conf
^((?!backup).)+(admin|kubelet)\.conf$

not matches multiple keywords

[!NOTE|label:samples:]

❌ foo-jenkins.domain.com
❌ foo-jenkins.domain.com/Monitor/
❌ marslo.github.com
❌ 127.0.0.1
 ^((?!.*\-jenkins\.[^\.]+\.com|.*Monitor/$|.*detail.*pipeline|.*api|marslo.github.*|shields.io|127.0.0.1|0.0.0.0|localhost).)*$

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