"A regular expression is a sequence of characters that specifies a match pattern in text."
Regular expressions are a notation to describe patterns of strings in a language. They are used to define regular languages.
Introduction to Regular Expressions: An overview of what Regular Expressions are and their importance in computer programming.
Character Classes: The use of square brackets to match and identify sets of characters.
Anchors: The use of special characters to match patterns at the beginning and end of a string.
Quantifiers: The use of special characters to match patterns that repeat or occur a certain number of times.
Alternations: The use of vertical bars to match two or more patterns, providing multiple options for a match.
Grouping and Backreferences: The use of parentheses to group patterns together and refer back to them later in the Regular Expression.
Lookarounds: The use of special characters to look ahead or behind a pattern without including it in the match result.
Greediness: The tendency of Regular Expressions to match as much as possible, and how it can be controlled with quantifiers and other operators.
Escape characters: The use of backslashes to remove special meaning from characters that would otherwise be interpreted as part of a Regular Expression.
Creating Regular Expressions: Best practices for building effective and efficient Regular Expressions, including testing and debugging techniques.
Basic Regular Expressions (BRE): These are a simple form of regular expressions that use basic metacharacters to match text patterns.
Extended Regular Expressions (ERE): These are a more advanced form of regular expressions that use extended metacharacters to match more complex text patterns.
Perl-Compatible Regular Expressions (PCRE): These are very powerful regular expressions that are commonly used in scripting and programming, especially in the Perl programming language.
JavaScript Regular Expressions (JSRE): These are a subset of PCRE that are used in JavaScript programming.
Java Regular Expressions (JRE): These are another set of regular expressions that are used in Java programming.
.NET Regular Expressions (NRE): These are another set of regular expressions that are used in the .NET Framework.
POSIX Regular Expressions (PRE): These are a standardized set of regular expressions that are used in Unix-based systems.
XML Schema Regular Expressions (XRE): These are used in XML schema validation to describe complex data patterns.
XPath Regular Expressions (XPRE): These are used in XPath expressions to select data from XML documents.
XQuery Regular Expressions (XQRE): These are used in XQuery expressions to manipulate XML data.
AWK Regular Expressions (AWKRE): These are used in AWK programs to manipulate text data.
Sed Regular Expressions (SEDRE): These are used in Sed commands to manipulate text data.
Grep Regular Expressions (GREPRE): These are used in grep commands to search for specific patterns in text files.
Vim Regular Expressions (VIMRE): These are used in the Vim text editor to search for and manipulate text data.
Emacs Regular Expressions (EMACSRE): These are used in the Emacs text editor to search for and manipulate text data.
"Usually such patterns are used by string-searching algorithms for 'find' or 'find and replace' operations on strings, or for input validation."
"Regular expression techniques are developed in theoretical computer science and formal language theory."
"The concept of regular expressions began in the 1950s when the American mathematician Stephen Cole Kleene formalized the concept of a regular language."
"They came into common use with Unix text-processing utilities."
"Different syntaxes for writing regular expressions have existed since the 1980s."
"One being the POSIX standard and another, widely used, being the Perl syntax."
"Regular expressions are used in search engines, in search and replace dialogs of word processors and text editors, in text processing utilities such as sed and AWK, and in lexical analysis."
"Regular expressions are used in search engines."
"In search and replace dialogs of word processors and text editors."
"In text processing utilities such as sed and AWK."
"Regular expressions are used in lexical analysis."
"Yes, regular expressions are supported in many programming languages."
"Regular expressions are used by string-searching algorithms for input validation."
"The concept of regular expressions began in the 1950s."
"Regular expressions are used by string-searching algorithms for 'find' or 'find and replace' operations on strings."
"Different syntaxes for writing regular expressions have existed since the 1980s."
"The American mathematician Stephen Cole Kleene formalized the concept of a regular language."
"They came into common use with Unix text-processing utilities."
"Regular expressions are used in search engines and lexical analysis." Note: The quotes provided above may not be exact, but they capture the essence of the corresponding answer.