We’ll cover the commands from above that get the most traffic here on DevCentral. The remaining documented list handling commands, lrepeat, lreverse, & dict, are not available within iRules. lsearch - See if a list contains a particular element.lreplace - Replace elements in a list with new elements.lrange - Return one or more adjacent elements from a list.lindex - Retrieve an element from a list.llength - Count the number of elements in a list.join - Create a string by joining together list elements.split - Split a string into a proper Tcl list.Most of the TCL commands for use in manipulating lists are available in iRules: Then remove the old cookie.We've talked about variables in the Getting Started with iRules series, but we're going to cover specifically the list object type of variable. # Rename a cookie by inserting a new cookie name with the same value as the original. For now the idea is to start making iRules look and feel more familiar. If you're not fully comfortable with the code yet, don't let that scare you, we'll dig into each part of what you'll need to build iRules as the series continues. You can see a basic example iRule below, this is what iRules look like, and we will explore the different parts of an iRule in far more depth in coming parts of this series. At the end of the day iRules is a network aware, customized language with which a user can add business and application logic to their deployment at the network layer. ![]() As such, rather than forcing them to submit requests for us to modify our core architecture every time they wanted to be able to use their F5 devices in a manner that slightly diverged from the collection of check boxes and drop downs available in the standard UI, we offered them iRules, and thereby a way to do what they need, when they need it. We recognized early on the need for users to be able to configure their systems to interact with network traffic in many ways that either we haven’t thought of, or are simply corner cases and/or in the minority of traffic being dealt with by our users. The idea behind iRules is to make the BIG-IP nearly infinitely flexible. ![]() IRules can route, re-route, redirect, inspect, modify, delay, discard or reject, log or … do just about anything else with network traffic passing through a BIG-IP. Whether you’re looking to do some form of custom persistence or rate limiting that isn’t currently available within the product’s built-in options, or looking to completely customize the user experience by granularly controlling the flow or even the contents of a given session/packet(s), that’s what iRules was built for. The idea is pretty straightforward iRules gives you the capability to write simple, network aware pieces of code that will influence your network traffic in a variety of ways. ![]() That’s pretty vague, though, so let’s try and define a bit more about what actually occurs within an iRule. To give a general introduction to iRules as a technology we’ll try to answer the following questions:Īn iRule, in its most simple terminology, is a script that executes against network traffic passing through an F5 device. Following a similar style as the first two introduction articles in this series, we’ll outline a few topics to cover, and then delve into them. Don't worry, we'll wait!īack for more? Great! Now that everyone is equally equipped, let’s dig in a bit to the meat of the topic at hand: iRules. If you’re new to F5, new to programming, new to both, or just looking for a refresher on some very rudimentary concepts and terminology, I recommend checking out the first two articles in this series so that we’re all on the same page as we wade into iRules proper. That may sound odd, but there has been some important foundational work to do before diving too deep into the technology behind iRules themselves. Welcome to the third installment of this series, wherein we will, for the first time, actually discuss iRules at length.
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