Chapter 2. Pipelines
2.0. Introduction
One of the fundamental concepts in a shell is called the pipeline. It also forms the basis of one of the most significant advances that PowerShell brings to the table. A pipeline is a big name for a simple concept—a series of commands where the output of one becomes the input of the next. A pipeline in a shell is much like an assembly line in a factory: it successively refines something as it passes between the stages, as shown in Example 2-1.
Get-Process | Where-Object { $_.WorkingSet -gt 500kb } | Sort-Object -Descending Name
In PowerShell, you separate each stage in the pipeline with the pipe (|) character.
In Example 2-1, the Get-Process
cmdlet generates objects that represent actual processes on the system. These process objects contain information about the process’s name, memory usage, process id, and more. The Where-Object
cmdlet, then, gets to work directly with those processes, testing easily for those that use more than 500 kb of memory. It passes those along, allowing the Sort-Object
cmdlet to also work directly with those processes, sorting them by name in descending order. This brief example illustrates a significant advancement in the power of pipelines: PowerShell passes full-fidelity objects along the pipeline, not their text representations.
In contrast, all other shells pass data as plain text between the stages. Extracting meaningful information from plain-text output turns the authoring of pipelines ...
Get Windows PowerShell Cookbook now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.