![]() Local VariablesĪll variables, unless otherwise specified, are created as local variables within an iRule. There are two main types of variables in iRules, local and global. For the purposes of this article, however, we're going to focus on the two main types of actual variables and leave the discussion of other data structures for later. ![]() From simple variables to arrays to tables and data groups, there are many ways to manage data in memory. This topic can creep in scope pretty darn quickly, given that variables are just a simple memory structure, and there are many different types of memory structures available to you via Tcl and iRules. What types of variables are available to me in iRules? #Basic variable reference to retrieve and use the value stored in memory You'll almost certainly be referencing the variables in relation to something or from another command. Simple referring to a variable within your code will do pretty much nothing. Of course calling them by themselves won't do much good. For instance "$integer" and "$hostname" would reference the values from the above example. To retrieve the value associated with a given variable you simply reference that variable directly and you will get the resulting value. The desired value is then stored in memory and associated with the variable name supplied. This can be a static or dynamic value, such as an integer or the result of a command. To set a variable in Tcl you simply use the set command and specify the desired value. There are two main functions when it comes to any variable: setting and retrieving. How do I work with variables in my iRule? You can, of course, modify, or delete variables at will also. Then, later, you can recall the value of that data by simply referencing the name you created to represent it. The idea is simple, take a piece of data, whether it's a number or a string or.anything, and store it in memory with a unique name. Whether it's storing the data from a math operation to be compared against a desired result, or checking to see if a given condition has been met yet, variables are at the very core of just about everything in programming, and aren't something that we could live without in modern coding. Variables are a large part of what allows dynamic programming to account for multiple conditions and use cases. Without them you'd be building static scripts to perform one off, iterative tasks. ![]() Every scripting language has variables of some form or another, and they're quite important in the grand scheme of things. those things would be stored in a variable. For instance if you want to store the hostname of an incoming connection so that you can reference that hostname on the response, or if you want to store the result of a given command, etc. This is done usually with the notion of using that data again at some point, recalling it to make use of it later in your script. Is there a performance impact when using variables?Ī variable, in simple terms, is a piece of data stored in memory. ![]()
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