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Expression

As explained in Learn PowerShell in a Month of Lunches: Fourth Edition, Covers Windows, Linux, and macOS

An expression is a PowerShell construct that evaluates to a value.

An expression is a PowerShell construct that evaluates to a value. In formatted output, it can calculate a custom property, rename its column, or change the displayed type. section 11.6

Expressions become practical when they are placed inside familiar commands:

  • Use arithmetic such as 100*10, assign the result to a variable, or write it directly. section 17.7
  • Use a formatting hash table to divide a process's VM value by 1MB and convert the result to an integer. section 11.6
Get-Process | Format-Table Name, @{name='VM(MB)';expression={$_.VM / 1MB 
 -as [int]}}

This command demonstrates an expression that produces a VM(MB) column from each process object. section 11.6

How Learn PowerShell in a Month of Lunches: Fourth Edition, Covers Windows, Linux, and macOS covers it

How deep it goes
Explains expressions through arithmetic, variables, formatting hash tables, and type conversion, but defers deeper operator coverage.
Examples
Demonstrates formulas, variable assignment, process memory conversion, custom column labels, and formatted process listings.
What it assumes
Assumes familiarity with basic commands such as Get-Process while introducing formulas, variables, and expressions through simple examples.
What you can do after
Apply expressions via PowerShell commands to calculate values, assign results, filter input, and improve formatted output.
How it connects
Connects expressions with hash tables, formatting cmdlets, arithmetic operators, type conversion, and pipelines.
Cover of Learn PowerShell in a Month of Lunches: Fourth Edition, Covers Windows, Linux, and macOS
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This explainer was generated by Manning's knowledge graph from the text of Learn PowerShell in a Month of Lunches: Fourth Edition, Covers Windows, Linux, and macOS. The section links point to the parts of the book it draws on.