Regular Expression Glossary
Specifies a location in a line or string. For example, the caret or circumflex character (
^) signifies the beginning of a line or string of characters, and the dollar sign character (
$), the end of a line or string.
Separating a list of regular expressions with a vertical bar (
|) character, indicating or. In other words, match any of the regular expressions separated by one or more | characters. In some applications, such as grep or sed that use basic regular expressions (BREs), the
|is preceded by a backslash, as in
\|. See also basic regular expressions.
American Standard Code for Information Interchange. A 128-character encoding scheme for English (Latin) characters developed in the 1960s. See also Unicode.
- atomic group
Refers to a previous regular expression captured with parentheses using a reference in the form of \1, \2, and so forth.
Stepping back, character by character, through an attempted match to find a successful match. Used with a greedy match, but not a lazy or possessive match. Catastrophic backtracking occurs when a regex processor makes perhaps thousands of attempts to make a match and consumes a vast amount (read most) of the computing resources available. One way to avoid catastrophic backtracking is with atomic ...