Regex ignore part of the string in matches -

suppose have tags object such:

["warn-error-fatal-failure-exception-ok","parsefailure","anothertag","syslog-warn-error-fatal-failure-exception-ok"] 

i able use regex match on "failure" exclude "warn-error-fatal-failure-exception-ok".

so in above case if used regex search failure should match failure on parsefailure , ignore rest.

how can accomplished using regex?

note: regex has exclude whole string "warn-error-fatal-failure-exception-ok"

edit

after documenting answer below, realized maybe looking is:

(?<!warn-error-fatal-)failure(?!-exception-ok) 

so i'm adding here in case fits looking better. regex looking "failure" using negative lookbehind , negative lookahead specify "failure" may not preceded "warn-error-fatal-" or followed "-exception-ok".

answer developed comments:

the following regex captures "failure" substring in "parsefailure" tag, , puts in group 1:

^.*"(?![^"]*warn-error-fatal-failure-exception-ok[^"]*)[^"]*(failure)[^"]*".*$ 

detail

i break regex in parts, , i'll explain each. first, let's forget in between first set of parentheses, , let's @ rest.

^.*"[^"]*(failure)[^"]*".*$ 

the important part of regex trying capture in group, word "failure" part of tag surrounded double-quotes. regular expression above matches whole test string, focuses on tag surrounded double-quotes , containing substring "failure".

^.*" matches character beginning of string quote

"[^"]*(failure)[^"]*" matches tag surrounded double-quotes , containing substring "failure". literally: double-quote, followed 0 or more characters not double-quotes, followed "failure", followed 0 or more characters not double-quotes, followed double-quote. parentheses capture word "failure" in group 1.

".*$ matches character double-quote end of test string

because [^"]*(failure)[^"]* matches tags containing substring "failure", ^.*"[^"]*(failure)[^"]*".*$ capture substring "failure" first tag containing string. in other words, capture "failure" warn-error-fatal-failure-exception-ok tag not want, exclude warn-error-fatal-failure-exception-ok tag being possible match tag portion of regex: [^"]*(failure)[^"]*. achieved negative lookahead:

(?![^"]*warn-error-fatal-failure-exception-ok[^"]*) 

this negative lookahead means: "the regular expression following negative lookahead can't match [^"]*warn-error-fatal-failure-exception-ok[^"]*". (?! , ) part of syntax. can read more here.

more breakdown

^ matches beginning of test string

.* matches character 0 or more times

" matches double-quote character

[^"]* matches character other double-quote character 0 or more times

(failure) matches word "failure", , since in parentheses, capture in group; in case, captured in group 1 because there 1 set of capturing parentheses. parentheses of negative lookahead non-capturing.

$ matches end of test string