A do-while loop in PowerShell runs its block once, then keeps repeating it as long as the condition after while is true. Because the check comes at the end, the block always runs at least one time: Output: A plain while loop checks its condition first instead, so its block may never run. Below I’ll … Read more
Think of a hashtable in PowerShell as a lookup list: each value sits under a key, and you get it back by that key instead of by position. Create one with @{ Key = ‘Value’ } and read it with $table[‘Key’]: Output: A hashtable is PowerShell’s built-in dictionary, so you’ll also see it called a … Read more
The PowerShell -in operator checks whether a value is in a collection, and -contains runs the same check with the collection written first. Both return True or False: They compare whole items, never parts of text, and that trips up a lot of scripts. I ran each example below in PowerShell 7 and Windows PowerShell … Read more
To convert a variable to a string in PowerShell, cast it with [string], call its ToString() method, or put it inside double quotes. For a number, all three give the same text: Output: They don’t always agree, though. Dates, decimals, arrays and $null each behave a little differently depending on which one you use, and … Read more
Get-FileHash is the built-in PowerShell cmdlet that calculates a file’s hash. Give it a path and you get a SHA256 hash; add -Algorithm MD5 when a download page lists an MD5 checksum: A hash is a fingerprint of a file’s content. Rename the file and the hash stays the same, but change a single character … Read more
Remove-Item with -Recurse is how you delete a directory in PowerShell, files and subfolders included. Add -Force so hidden and read-only files don’t stop it: Output: There’s no Recycle Bin and no undo. I ran everything below in a throwaway test folder, C:\psfaqs\Purge, in PowerShell 7.6 and Windows PowerShell 5.1. Where the two behaved differently, … Read more
PowerShell function parameters live in a param() block at the top of the function. Each one is a variable with an optional type and default value, and you pass it by name when you call the function: Output: That’s the whole idea. Once a function has parameters, it acts like a small cmdlet, with named … Read more
A PowerShell foreach loop repeats a block of code once for each item in a collection: an array, a folder of files, command output, or a number range such as 1..10. The current item lands in the variable you name before in: Here’s a real one that walks through an array of office names: Output: … Read more
To make PowerShell wait for a command to finish, start it with Start-Process -Wait. Add -PassThru as well, and you get the process object back, so you can read its exit code once it closes: Output: Without -Wait, Start-Process hands control back right away while the program keeps running. I’ll show what -Wait really waits … Read more
PowerShell doesn’t ship a grep command, but Select-String does the same job. Give it a pattern and a file, and it returns every matching line, the way grep in PowerShell should: Below, I map the grep options you already know to Select-String parameters and run each one on a sample log. Every result came from … Read more