Regular expressions operate by moving character by character, from left to right, through a piece of text. When regex finds a character that matches the first piece of the expression, it looks to find a continuous sequence of matching characters.<\/p>\n\n\n
Match text<\/strong><\/p>\n Match the string “abc”<\/p>\n Alternation<\/strong><\/p>\n Match the string “abc” OR “def” Character Sets<\/strong><\/p>\n Square brackets [] are used to match one character from a series of possible characters<\/p>\n Match the string where any combination of the series characters are used, e.g.: “abcefgij” or “abdefgij” or “abdefhij” or “abdef ij” ^ character negates the character set, so will allow any character OTHER than the characters used<\/p>\n “abzefgij” would match, “abdefgij” would not.<\/p>\n Wildcards<\/strong><\/p>\n . = Match a single character<\/p>\n Will match any 3 characters, but there must be 3 characters. “qur.” would match, “qurk” wouldn’t match<\/p>\n See also the “Quantifiers – 0 or More, 1 or More” section below for multicharacter wildcard options<\/em><\/p>\n Ranges<\/strong><\/p>\n Use a hyphen to specify a range of character values that are allowed (remember we are still only matching to a single character)<\/p>\n [a-c] is the same as saying [abc]<\/p>\n [a-cA-D] is the same as saying [abcABCD]<\/p>\n Some typical ranges that are often used<\/p>\n Shorthand Character Classes<\/strong><\/p>\n \u201cword character\u201d class, represents regex range [A-Za-z0-9_]<\/p>\n \u201cdigit character\u201d class, represents regex range [0-9]<\/p>\n \u201cwhitespace character\u201d, represents regex range [ \\t\\r\\n\\f\\v] \u201cnon-word character\u201d class, represents regex range [^A-Za-z0-9_] (any character not included in the range represented by \\w )<\/p>\n \u201cnon-digit character\u201d class, represents regex range [^0-9] (any character not included in the range represented by \\d )<\/p>\n \u201cnon-whitespace character\u201d, represents regex range [^ \\t\\r\\n\\f\\v] (any character that is not included in the range represented by \\s )<\/p>\n An example: \\d\\s\\w\\w<\/p>\n Matches a digit character, followed by a whitespace character, followed by 2 word characters<\/p>\n Grouping<\/strong><\/p>\n Groups a section of the regex expression. E.g. Hello (Dave|David)! Quantifiers – Fixed<\/strong><\/p>\n Specify the number of characters to match using the last expression<\/p>\n Specify the quantity of the previous character definition to match Quantifiers – Optional<\/strong><\/p>\n Specify that the previopus character definition is optional<\/p>\n Some examples:<\/p>\n “abc?d” will match for “abd” and “abcd” Quantifiers – 0 or More, 1 or More<\/strong><\/p>\n Preceeding character doesn’t need to appear, or can appear an unlimited number of times<\/p>\n Preceeding character must appear 1 or more times<\/p>\n Examples<\/p>\n “abc*d” will match for “abd”, “abcd”, “abcccccd”, etc <\/p>\n Anchors (start and end markers)<\/strong><\/p>\n Start of string marker – will not match if tested string starts before this point<\/p>\n End of strng marker – will not match if tested string continues past this point<\/p>\n Examples<\/p>\n “^bcd ef” will match “bcd ef”, “bcd efghi”, etc, but not match for “abcd ef” <\/p>\n\n\n Characters used as special characters in regex that you need to escape if you want to specify that actual character in your regex:<\/p>\n\n\n <\/p>\n\n\n <\/p>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" Regular expressions operate by moving character by character, from left to right, through a piece of text. When regex finds a character that matches the first piece of the expression, it looks to find a continuous sequence of matching characters. Match text abc Match the string “abc” Alternation abc|def Match the string “abc” OR “def”Note […]<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[69],"tags":[],"class_list":["post-3945","post","type-post","status-publish","format-standard","hentry","category-regex-regular-expressions"],"_links":{"self":[{"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/posts\/3945","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/comments?post=3945"}],"version-history":[{"count":29,"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/posts\/3945\/revisions"}],"predecessor-version":[{"id":3997,"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/posts\/3945\/revisions\/3997"}],"wp:attachment":[{"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/media?parent=3945"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/categories?post=3945"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ibex.tech\/cloud\/wp-json\/wp\/v2\/tags?post=3945"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}abc<\/pre>\n
abc|def<\/pre>\n
Note that the | symbol matches the entire expression before or after itself. Use Grouping (see below) to OR specific parts of the regex expression. e.g. “Hello (Dave|David)!”<\/p>\nab[cd]ef[gh ]ij<\/pre>\n
“abcdefgij”, for example, will not match.<\/p>\nab[^cd]ef[gh]ij<\/pre>\n
...<\/pre>\n
(If you need o use a period as a character in a regex expression, you escape it with a forward slash “\\.” )<\/p>\n...\\.<\/pre>\n
[a-z]
[A-Z]
[a-zA-Z]
[0-9]
[a-zA-Z0-9]<\/pre>\n\\w<\/pre>\n
\\d<\/pre>\n
\\s<\/pre>\n
(Matches a single space, tab, carriage return, line break, form feed, or vertical tab)<\/p>\n\\W<\/pre>\n
\\D<\/pre>\n
\\S<\/pre>\n
()<\/pre>\n
will match for “Hello Dave!”, “Hello David!”, <\/p>\n{}<\/pre>\n
“\\w{4}” would match exactly 4 word characters
“\\w{2,5}” would match min 2 word characters and max 5 word characters. The quantifier is greedy – it will match the greatest quantity of characters it possibly can when a min and max is specified. <\/p>\n?<\/pre>\n
“Hello (cheeky )?boy”, will match for “Hello boy” and “Hello cheeky boy”
“Hello (loud |cheeky )?boy”, will match for “Hello boy”, “Hello cheeky boy” and “Hello loud boy”<\/p>\n*<\/pre>\n
+<\/pre>\n
“abc+d” will match for “abcd”, “abcccccd”, etc, but not for “abd”<\/p>\n^<\/pre>\n
$<\/pre>\n
“^bcd ef$” will match “bcd ef”, but not match for “abcd ef” or “bcd efghi”<\/p>\nSpecial character escaping<\/h4>\n\n\n\n
\\\\
\\.
\\?
\\*
\\+
\\{
\\(
\\)
\\^
\\$
\\[
\\|<\/pre>\n