background preloader

Regular Expressions Reference - Basic Syntax

Regular Expressions Reference - Basic Syntax
The regular expressions reference on this website functions both as a reference to all available regex syntax and as a comparison of the features supported by the regular expression flavors discussed in the tutorial. The reference tables pack an incredible amount of information. To get the most out of them, follow this legend to learn how to read them. The tables have six columns for each regular expression feature. The final two columns indicate whether your two chosen regular expression flavors support this particular feature. When this legend says "all versions" or "no version", that means all or none of the versions of each flavor that are covered by the reference tables: For the .NET flavor, some features are indicated with "ECMA" or "non-ECMA". For the std::regex and boost::regex flavor there are additional indicators ECMA, basic, extended, grep, egrep, and awk. For the PCRE2 flavor, some replacement string features are indicated with "extended". Related:  Regular Expressions

PowerShell Tutorial – Try Catch Finally and error handling in PowerShell One of the key parts of any good PowerShell script is error handling. Even in the shortest script, being able to handle errors helps to ensure that an unexpected event will not go on to wreck the system you are working on. Take the example below. Every week in our sample company (MyCompany.Com) Human Resources are going to upload a list telling us who should have access to the Expenses database. If a name isn’t in the list from HR we’re going to remove it from the group and that user will no longer be able to log expense claims: $AuthorizedUsers= Get-Content \\ FileServer\HRShare\UserList.txt $CurrentUsers=Get-ADGroupMember "Expenses Claimants" Foreach($User in $CurrentUsers){ If($AuthroizedUsers -notcontains $User) { Remove-ADGroupMember -Identity "Expenses Claimants" -User $User }} Now, you can see where this is going to go wrong. Terminating and Non-Terminating Errors One of the key things to know when catching errors is that only certain errors can be caught by default.

Example: Matching Floating Point Numbers with a Regular Expression This example shows how you can avoid a common mistake often made by people inexperienced with regular expressions. As an example, we will try to build a regular expression that can match any floating point number. Our regex should also match integers and floating point numbers where the integer part is not given. At first thought, the following regex seems to do the trick: [-+]? Spelling out the regex in words makes it obvious: everything in this regular expression is optional. Not escaping the dot is also a common mistake. When creating a regular expression, it is more important to consider what it should not match, than what it should. Here is a better attempt: [-+]? This is a far better definition. We can optimize this regular expression as: [-+]? If you also want to match numbers with exponents, you can use: [-+]? Did this website just save you a trip to the bookstore?

Regular-Expressions.info - Regex Tutorial, Examples and Reference - Regexp Patterns PowerShell: Creating Custom Objects - TechNet Articles - United States (English) Link to Parent: PowerShell - Deep Dive and Best Practice Different Methods For Creating Custom Objects 1. You can use the New-Object cmdlet to generate an object of any type. You can also specify -ComObject to create a COM Object, but that is not covered in this article. #Example 1.1 $obj = new-objectpsobject There are two different ways to add members to an object 1.1 Add-Member The best (and most verbose) method is to use Add-Member. #Example 1.2 $obj = New-Object PSObject Add-Member -InputObject $obj -MemberType NoteProperty -Name customproperty -Value "" A note about this is that you need to specify a value where as with select-object you do not. 1.2 Hash If you have a lot of properties to create and they all have values you can assign a hash table to the object to quickly create the objects properties. #Example 1.3 $props = @{ Property1 = 'one' Property2 = 'two' Property3 = 'three' $object= new-objectpsobject -Property $props 1.3 Hash with V3 #Example 1.4 $obj = [PSCustomObject]@{ 2. [int]$n1=$null

Regex Tutorial - \b Word Boundaries The metacharacter \b is an anchor like the caret and the dollar sign. It matches at a position that is called a "word boundary". This match is zero-length. There are three different positions that qualify as word boundaries: Before the first character in the string, if the first character is a word character. Simply put: \b allows you to perform a "whole words only" search using a regular expression in the form of \bword\b. Exactly which characters are word characters depends on the regex flavor you're working with. Most flavors, except the ones discussed below, have only one metacharacter that matches both before a word and after a word. Since digits are considered to be word characters, \b4\b can be used to match a 4 that is not part of a larger number. \B is the negated version of \b. Looking Inside The Regex Engine Let's see what happens when we apply the regex \bis\b to the string This island is beautiful. \b cannot match at the position between the T and the h. Tcl Word Boundaries

Regular Expression HOWTO — Python v2.7.2 documentation Introduction The re module was added in Python 1.5, and provides Perl-style regular expression patterns. Earlier versions of Python came with the regex module, which provided Emacs-style patterns. Regular expressions (called REs, or regexes, or regex patterns) are essentially a tiny, highly specialized programming language embedded inside Python and made available through the re module. Regular expression patterns are compiled into a series of bytecodes which are then executed by a matching engine written in C. The regular expression language is relatively small and restricted, so not all possible string processing tasks can be done using regular expressions. Simple Patterns We’ll start by learning about the simplest possible regular expressions. For a detailed explanation of the computer science underlying regular expressions (deterministic and non-deterministic finite automata), you can refer to almost any textbook on writing compilers. Matching Characters \d \s \w Repeating Things Grouping

Script Windows Update PowerShell Module Verified on the following platforms This script is tested on these platforms by the author. It is likely to work on other platforms as well. If you try it and find that it works on another platform, please add a note to the script discussion to let others know. Online peer support For online peer support, join The Official Scripting Guys Forum! Disclaimer The sample scripts are not supported under any Microsoft standard support program or service. Example: Matching Numeric Ranges with a Regular Expression Since regular expressions deal with text rather than with numbers, matching a number in a given range takes a little extra care. You can't just write [0-255] to match a number between 0 and 255. Though a valid regex, it matches something entirely different. [0-255] is a character class with three elements: the character range 0-2, the character 5 and the character 5 (again). This character class matches a single digit 0, 1, 2 or 5, just like [0125]. Since regular expressions work with text, a regular expression engine treats 0 as a single character, and 255 as three characters. The regex [0-9] matches single-digit numbers 0 to 9. [1-9][0-9] matches double-digit numbers 10 to 99. Matching the three-digit numbers is a little more complicated, since we need to exclude numbers 256 through 999. 1[0-9][0-9] takes care of 100 to 199. 2[0-4][0-9] matches 200 through 249. Putting this all together using alternation we get: [0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5].

Advanced Regular Expression Tips and Techniques Twice a month, we revisit some of our readers’ favorite posts from throughout the history of Nettuts+. Regular Expressions are the Swiss Army knife for searching through information for certain patterns. They have a wide arsenal of tools, some of which often go undiscovered or underutilized. Today I will show you some advanced tips for working with regular expressions. Adding Comments Sometimes, regular expressions can become complex and unreadable. For example, here is something we might use to check for US phone numbers. It can become much more readable with comments and some extra spacing. Let's put it within a code segment. The trick is to use the 'x' modifier at the end of the regular expression. Using Callbacks In PHP preg_replace_callback() can be used to add callback functionality to regular expression replacements. Sometimes you need to do multiple replacements. Let's look at this example, where we have an e-mail template. Notice that each replacement has something in common. Other

What happened to a CustomMenu property? - get-life | add-powershell If you'd like to customize your Windows PowerShell ISE be prepared for some breaking changes in Windows PowerShell ISE that comes with Windows 7 RC (May I call it Windows PowerShell ISE RC?). In Windows PowerShell ISE CTP3 $psISE, custom host variable, has following properties: PS C:\> $psISE | gm -MemberType property TypeName: System.Management.Automation.Host.PSGHost Name MemberType Definition ---- ---------- ---------- CurrentOpenedFile Property System.Management.Automation.Host.OpenedFile CurrentOpenedFile {get;} CurrentOpenedRunspace Property System.Management.Automation.Host.OpenedRunspace CurrentOpenedRunspace {get;} CustomMenu Property System.Management.Automation.Host.PSMenuItem CustomMenu {get;} OpenedRunspaces Property System.Management.Automation.Host.OpenedRunspaceCollection OpenedRunspaces {get;}Options Property System.Management.Automation.Host.Options Options {get;} Same command in Windows PowerShell ISE RC will give renamed type and properties: Bingo! What the fluff?!

Regular Expression Examples Below, you will find many example patterns that you can use for and adapt to your own purposes. Key techniques used in crafting each regex are explained, with links to the corresponding pages in the tutorial where these concepts and techniques are explained in great detail. If you are new to regular expressions, you can take a look at these examples to see what is possible. RegexBuddy offers the fastest way to get up to speed with regular expressions. Oh, and you definitely do not need to be a programmer to take advantage of regular expressions! Grabbing HTML Tags <TAG\b[^>]*>(.*?) <([A-Z][A-Z0-9]*)\b[^>]*>(.*?) Trimming Whitespace You can easily trim unnecessary whitespace from the start and the end of a string or the lines in a text file by doing a regex search-and-replace. More Detailed Examples Numeric Ranges. Matching a Floating Point Number. Matching an Email Address. Matching an IP Address. Matching Valid Dates. Finding or Verifying Credit Card Numbers. Matching Complete Lines.

CIM_Error class CIM_Error is a specialized class that contains information about the severity, cause, recommended actions and other data related to the failure of a CIM Operation. Instances of this type can be included as part of the response to a CIM Operation. CIM_Errors like CIM_Indications do not persist, and do not have keys. Currently, this is only allowed by defining a concrete class with the Indication qualifier. Until the CIM Specification is modified to allow other concrete classes without keys, the CIM_Error class must be qualified by both Indication and Exception. After this, the Indication qualifier can be removed. The CIM_Error class must be qualified with a Version qualifier. Important The DMTF (Distributed Management Task Force) CIM (Common Information Model) classes are the parent classes upon which WMI classes are built. The following syntax is simplified from Managed Object Format (MOF) code and includes all of the inherited properties. Syntax Members Properties CIMStatusCode ErrorSource

Popular Tools, Utilities and Programming Languages That Support Regular Expressions These tools and utilities have regular expressions as the core of their functionality. grep - The utility from the UNIX world that first made regular expressions popular PowerGREP - Next generation grep for Microsoft Windows RegexBuddy - Learn, create, understand, test, use and save regular expressions. RegexMagic - Generate regular expressions using RegexMagic's powerful patterns instead of the cryptic regular expression syntax. General Applications with Notable Support for Regular Expressions There are a lot of applications these days that support regular expressions in one way or another, enhancing certain part of their functionality. EditPad Lite - Basic text editor that has all the essential features for text editing, including powerful regex-based search and replace. EditPad Pro - Convenient text editor with a powerful regex-based search and replace feature, as well as regex-based customizable syntax coloring and file navigation. Programming Languages and Libraries Databases

Related: