/tags/regex/ Recent content in regex on Shylock Hg Hugo -- gohugo.io en-us Thu, 05 Apr 2018 00:00:00 +0000 /post/2018/04/05/flavor-of-regular-expression/ Thu, 05 Apr 2018 00:00:00 +0000 /post/2018/04/05/flavor-of-regular-expression/ POSIX It’s POSIX specification for regular expression in UNIX-like environment tools,such as vim,sed,awk,grep. BRE |Metacharacters|Meaning| |:–|:–| |.|match any one character| |\\|escape character| |[|| |^|anchor for start of characters,complement set in backet expression| |$|anchor for end of characters| |*|| note:in GNU implement,you can use ERE special metacharacters by \\. BRE tools:sed,grep ERE |Metacharacters|Meaning| |:–|:–| |(|| |)|| |{|| |}|| |+|| |?|| |\||| note:ERE include all BRE metachatacters. ERE tools:awk,egrep,sed -E POSIT character class example: [:digit:] /post/2018/03/31/overview-of-regular-expression/ Sat, 31 Mar 2018 00:00:00 +0000 /post/2018/03/31/overview-of-regular-expression/ Base elements literal characters,(eg.abc) meta characters,(eg..) note:all valid regex is composed by printable ascii characters reducing rules position anchor,(eg.$) lookground,(eg.``) set character class,(eg.[0-9]) shorthand,(eg.\d) unicode properties,(eg.\p{L}) dot match,(eg..) escape character non-printable characters,(eg.\t) literal meta characters,(eg.\\) non ascii characters,(eg.\uFFFF) logic alternation,(eg.a|b) repetition(greedy,lazy),(eg.[0-9]+) grouping and caturing group,(eg.set(Value)?) group without caturing,((eg.set(?:Value)?) back reference,(eg.([abc])=\1) named group,(eg.(?<mygroup>[abc])=\k<mygroup>)