Recursion of the only pattern of the numbered capturing group, here group 1 The number of steps necessary to obtain the result. Whenever possible, it is always better to “anchor” the lookarounds, to reduce Placed at the end of the pattern prevents to select within a tag or a style embedded in the file. Negative lookahead (to be placed after the selection) Positive lookahead (to be placed after the selection) Twoĭifferent groups can use the same name. Pattern by (?P=name) and in the replace by \g. The selection can be recalled later in the search Atomic groups do notīranch reset group: the branches of the alternations included in theĮxpression share the same group numbers (?expression)
Try other combinations with the expression.
Passes, and if the rest of the pattern fails, it will not backtrack to Group that does not capture the selection (?>expression)Ītomic Group: As soon as the expression is satisfied, the regexp engine Sequence number of the capturing group (starting at 1 in reading order) (?:expression) In the search or replace patterns with \n, where n is the The most useful anchors for text processing are:Ĭapturing group, which stores the selection and can be recalled later Anchors ¶Īn anchor is a way to match a logical location in a string, rather than aĬharacter. Selects Blabla, in the strings Blabla or “Blabla or Blabla”, but not in “Blabla”. Pattern_to_exclude(*SKIP)(*FAIL)|pattern_to_select That either the preceding or the following expression can match. The | character in a regular expression is a logical OR. ? follows a quantifier to make it lazy.Īvoid putting two in the same expression, the result can be unpredictable.īeware of nesting quantifiers, for example, the pattern (a*)*, as itĮxponentially increases processing time. Number of occurrences between 0 and the maximum value includedīy default, with quantifiers, the regular expression engine is greedy: itĮxtends the selection as much as possible. Number of occurrences between the minimum value included and the infinite
Number of occurrences between the minimum and maximum values included Number of occurrences of the expression preceding the quantifierĠ or 1 occurrence of the expression. Use the “dot all” checkbox or the (?s) regexp modifier to include the newline character. Space, non-breaking space, tab, return lineĪny character except newline. ] +> to select an HTML tag Shorthand character classes ¶Īny non-numeric character (same as )Īn alphanumeric character ( ) including characters with accent mark and ligatures Abbreviated classes can be used inside a class The characters - exclude what follows themĪll letters (including foreign accented characters). The caret (^) placed at the beginning of the class excludes the characters of the class (complemented class) To include the dash in a class, you must put it at the beginning or at the end so as not to confuse it with the hyphen that specifies a range of charactersĪny character except a digit. Uppercase or lowercase letters, or a dash. Lowercase letters from a to z or numbers from 0 to 9
Does not include characters with accent mark and ligatures Regexp engine available in most parts of calibre.Ĭharacter classes are useful to represent different groups of characters, This checklist summarizes the most commonly used/hard to remember parts of the
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