05-conditional-trycatch

Math & Comparison

Supported

• +, -, *, /, %

Powershell do not use == or !=, <=

(1 -eq 2)

• -ge/le/gt/lt - common comparison, greater/less than or equal to
• by adding c into eq will make the search case sensitive

File based operation with `Test-Path

Test-Path $filePath

• whether a folder or file exist

If/Else

if(condition){ action } elseif(){} else {}

• uses () for condition and {} for action

(-not $true) # negate a condition
($true -and -or $false) # multiple conditions

Switch

Where there are many conditions

switch($variable){
	"value" {action; break}
	"value2" {action2; break}
	default {defaultAction}
}

• similar to dictionary, the lines can be shortened with ;
• best practice to put break so only 1 case executes

If the switch statement need a conditional with $variable, use {$_}

switch($variable){
	{$_ -eq 123} {action}
}

Try catch will only catch terminating error

try{ failed } catch { echo failed }

To adjust error types of some commands

command -ErrorAction $

• continue - will keep executing and show error
• ignore - continue and not show anything
• inquire - ask the user what to do
• silentlycontinue - store into error variable and continue
• stop - stop executing the script
• break - enter debug mode (VSCode)

Get Exception message

$_.Exception.Message

Raise an error

throw "custom error"

Change default error action (similar to `set -e)

$ErrorActionPreference = "Stop"

Errors are stored in a variable $Error

• the latest error is stored in the first index `$Error[0]