Notepad regular expressions: description, replacement and examples

Table of contents:

Notepad regular expressions: description, replacement and examples
Notepad regular expressions: description, replacement and examples

Notepad's regular expression is a formal language theory, a sequence of characters that defines a search pattern. Typically, this pattern is then used by string search algorithms for "find" or "find and replace" operations on strings. But let's take everything in order and consider this topic in more detail.

Description of how regular expressions work

The concept originated in the 1950s when the American mathematician Stephen Cole Kleene formalized the description of ordinary language. This concept has been widely used with Unix text processing utilities. Since the 1980s, there have been various syntaxes for writing regular expressions, one of which is the POSIX standard and the other, widely used, is the Perl syntax.

notepad regular expressions
notepad regular expressions

Notepad regular expressions are used in search engines, for searching and replacing dialogs in word processors and text editors, in word processing utilities such as sed and AWK, and in lexical analysis. Many programming languages provide regularexpressions built in or through libraries.

How to remove blank lines in Notepad regular expressions?

The term "regular expressions" is often used to refer to a specific standard textual syntax (other than the mathematical notation described below) for representing patterns that must match text. Each character in a regular expression is treated as either a metacharacter (with its special meaning) or a normal character (with its literal meaning). Together, metacharacters and literal characters can be used to identify textual material of a given pattern, or to process multiple instances.

otepad regular expression replacement
otepad regular expression replacement

Patterns can range from exact equality to very general similarity controlled by metacharacters. The metacharacter syntax is designed specifically to represent given targets in a concise and flexible way to control text processing automation from various inputs. This is convenient for typing using a standard ASCII keyboard.

Notepad regular expression examples and patterns

A regular expression, often referred to as a pattern, is an expression used to specify a set of strings required for a specific purpose. An easy way to specify a finite set of rows is to list its elements. However, there are often more concise ways to specify the desired set of rows. For example, a set containing three strings, Handel, Händel, and Haendel, can be given by the pattern H (ä | ae?) Ndel, since this pattern matches each ofthree lines. In most formalisms, if there is at least one Notepad regular expression that matches a certain set, there are an infinite number of other regular expressions that also match it, and the specification is not unique. Most formalisms provide the following operations for building regular expressions.

History of occurrence

Regular expressions originated in 1951, when mathematician Stephen Cole Kleene described ordinary languages using a mathematical notation called regular sets. They originated in theoretical computer science, in subfields of automata theory (computation models), description and classification of formal languages. Other early implementations of pattern matching include the SNOBOL language, which does not use regular expressions but its own pattern-matching constructs.

regular expressions notepad examples
regular expressions notepad examples

Line breaks in Notepad regular expressions have been widely used since 1968 for two purposes: pattern matching in a text editor and lexical analysis in a compiler. Among the first appearances of regular expressions in programmatic form was that Ken Thompson built the Klein notation in the QED editor as a means for pattern matching in text files. For speed, Thompson implemented regular expression comparison using just-in-time (JIT) compilation to IBM code 7094 in a compatible time system-an important early example of JIT compilation. He later added this capability to the Unix ed editor, which ineventually led to the use of the popular grep search tool to use regular expressions. Around the same time that Thompson developed QED, a group of researchers including Douglas T. Ross introduced a tool based on regular expressions, which are used for lexical analysis in compiler design.

Development of the concept

Many variations of these original Notepad regular expression substitution forms were used in Unix programs at Bell Labs in the 1970s, including vi, lex, sed, AWK, and expr, as well as other utilities such as Emacs. Subsequently, these forms were adopted by a wide range of programs, and they were in the POSIX.2 standard in 1992.

notepad regular expressions in search
notepad regular expressions in search

In the 1980s, more complex regular expressions originated in Perl, which was originally derived from a regular expression library written by Henry Spencer (1986). He later wrote an implementation of extended regular expressions for Tcl. The Tcl library is a hybrid implementation of NFA/DFA with improved performance.

Software projects that have used Spencer's Tcl regular expression implementation include PostgreSQL. Perl later extended to the original Spencer library to add many new features, but has yet to implement Spencer's extended regular expressions in terms of performance or Unicode handling. Part of the effort in the development of Perl 6 is to improve the integration of regular expressions and increase their capabilities, allowingdetermine the parsing of grammatical expressions.

notepad regular expression line break
notepad regular expression line break

The result of this is a mini-language called Perl 6 rules, which are used to define the grammar and also provide a tool for programmers in that language. These rules support existing regular expression features.

The current stage of development

The use of Notepad regular expressions in search and in structured information standards for document and database modeling began in the 1960s and expanded in the 1980s as industry standards such as ISO SGML were consolidated. The core of the structure specification language standards consists of regular expressions. Since 1997, Philip Hazel has developed PCRE (Perl Compatible Regular Expressions), which attempts to closely mimic Perl's regular expression functionality and is used by many modern tools, including PHP and Apache HTTP Server.

Scope and use

Today, regular expressions are widely supported in programming languages, word processing programs, advanced text editors, and some other programs. Regular expression support is part of the standard library of many programming languages, including Java and Python, and built into the syntax of others, including Perl and ECMAScript.

notepad remove empty lines regex
notepad remove empty lines regex

The implementation of regular expressions is often referred to as the regular expression engine, and for reusemultiple libraries available.

Popular topic

Editor's choice

  • Windows 7 password bypass: possible methods and recommendations from experts
    Windows 7 password bypass: possible methods and recommendations from experts

    The fact that users (most often computer administrators) protect Windows operating systems from unauthorized use, for example, in their absence at the computer, does not surprise anyone. However, often the administrator may not give the registered user enough rights to perform any actions or set personal settings, and therefore it may be necessary to log in with an administrator registration

  • How to remove a virus from a flash drive without losing data?
    How to remove a virus from a flash drive without losing data?

    Removable USB storage devices in the form of the most common flash drives are susceptible to viruses no less than hard drives with operating systems installed on them. And it is often quite problematic to identify the presence of such a threat or neutralize it. How to remove a virus from a flash drive and restore files (hidden or infected) will be discussed further

  • File viruses are computer code to achieve goals bypassing security systems
    File viruses are computer code to achieve goals bypassing security systems

    File viruses are computer code to achieve goals bypassing security systems. This is what inspired people to create antiviruses, what allows hackers to learn and steal millions of dollars every day

  • PC prevention for stable operation - expert advice. Computer help
    PC prevention for stable operation - expert advice. Computer help

    The fact that almost all modern computer systems require constant care, apparently, all users know. But not everyone has a clear enough idea of what this should manifest itself in. To keep the computer, operating system and installed applications in the most efficient condition, it is necessary to carry out preventive maintenance of the PC software and monitor the hardware components (installed equipment)

  • Detector software: what is it in the field of anti-virus protection?
    Detector software: what is it in the field of anti-virus protection?

    Apparently, many users of modern computer systems have heard or know that there are so-called detector programs. What they are is easy to understand if you just turn to the translation or interpretation of the English word detect, which literally means “to detect”