PowerShell: post-project reflections, or: PowerShell foundations

23 May, 2024

Whew!

For a recent project, I wrote around almost ~2,000 lines of PowerShell code. Not that quantity means much by itself, but it was a significant effort, and it was definitely entering the region where "normal people" with pretty good Excel skills would not have been able to do the task with the same rigour or expedience.

This was a chunk of work that solved a real business problem. Below, I list the techniques that I used. It is just applying the basics over and over again.

I've ordered the list below from fundamental to a bit more advanced. There are about 20 major dot points or concepts here.

I would consider this a pretty robust foundation that, if I had a grad under my wing, I would get them to learn and practice.

Techniques

"Coding"

• Setting variables

• Manually creating arrays

  • $numbersAsWords = @("one", "two", "three)
  • $numbersAsNumbers = @(1, 2, 3)

• Manually creating hashtables

  • Using this as an "enum" (this is more advanced)

Reading and writing data

• Reading data files

  • Get-Content $file.json | ConvertTo-Json
  • Import-Csv $file.csv
  • Import-Csv $file.csv -Delimiter "`t"

• Writing data files

  • Export-CSV
  • Export-CSV -Encoding unicode -Delimiter "`t"
    • Especially relevant if there are special characters (like diacritics in European names)
  • Set-Content, or >
  • Add-Content, or >>

Checking stuff

• Checking if something is a part of something else (-in for arrays, -like for text)

• Checking logic, using -eq, -ne, -not, -gt, -lt

Filtering

• Filtering a table, using Where-Object (or ?)

• Array access (including after splitting a phrase into an array)

  • $wordParts[0]
  • $wordParts[1..4]

• Select-Object

  • -First
  • -Last
  • -Property
  • -Unique

If

• if() {} else {}
• switch

Doing stuff over and over

• Doing a ForEach-Object (or %) loop on a table, to do:

  • Changing properties on each object in a table
  • Adding more properties (i.e. adding moe columns) onto a table

• Grouping, and looping through groups using Group-Object

• Writing functions so they can be re-used

  • function eatSomething ($food) {}

Text manipulation

• Text manipulation

  • .split or -split
  • -join
  • .Substring()
  • .Trim()

• Using string interpolation

  • "I like to eat $food"
  • "I like it when my $food is $($food.colour)"

Advanced stuff

• Dot-sourcing
• Using advanced data types
  • like [List[]] and [StringBuilder]
• Stopwatch
• Using code from a library/module (someone else's code)

#powershell