One of the fundamental concepts in a shell is called the pipeline. It also forms the basis of one of PowerShell’s most significant advances. 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.
Example 2-1. A PowerShell pipeline
Get-Process | Where-Object WorkingSet -gt 500kb | Sort-Object -Descending Name
In PowerShell, you separate each stage in the pipeline with
the pipe (
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.
Get-Process cmdlet generates
output, it passes it along. Simultaneously, the
Where-Object cmdlet gets to work directly with
those processes, testing easily for those that use more than 500 KB of
memory. It passes those along immediately as it processes them, allowing
Sort-Object cmdlet to also work
directly with those processes and sort them by name in descending
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 ...