Tag: PowerShell Cheat Sheet

# Do something if 1 is equal to 1
if (1 -eq 1) { }

# Loop while a condition is true (always executes at least once)
do { 'hi' } while ($false)

# While loops are not guaranteed to run at least once
while ($false) { 'hi' }
# Do something indefinitely
while ($true) { }
# Break out of an infinite while loop conditionally
while ($true) { if (1 -eq 1) { break } }

# Iterate using a for..loop
for ($i = 0; $i -le 10; $i++) { Write-Host $i }
# Iterate over items in an array
foreach ($item in (Get-Process)) { }

# Use the switch statement to perform actions based on conditions. Returns string 'matched'
switch ('test') { 'test' { 'matched'; break } } 

# Use the switch statement with regular expressions to match inputs
# NOTE: $PSItem or $_ refers to the "current" item being matched in the array
switch -regex (@('Trevor', 'Daniel', 'Bobby')) { 
  'o' { $PSItem; break } 
}

# Switch statement omitting the break statement. Inputs can be matched multiple times, in this scenario.
switch -regex (@('Trevor', 'Daniel', 'Bobby')) {
  'e' { $PSItem }
  'r' { $PSItem }
}

# A basic PowerShell function

function add ($a, $b) { $a + $b }

# A PowerShell Advanced Function, with all three blocks declared: BEGIN, PROCESS, END

function Do-Something {
  [CmdletBinding]()]
  param ()
  begin { }
  process { }
  end { }
}

# Do While Loop

$a=1
Do {$a; $a++}
While ($a –lt 10)

# Do Until Loop

$a=1
Do {$a; $a++}
Until ($a –gt 10)

# For Loop

For ($a=1; $a –le 10; $a++)
{$a}

# ForEach – Loop Through Collection of Objects

Foreach ($i in Get-Childitem c:\windows)
{$i.name; $i.creationtime}

Below is a regular expression list

#Match while tagging match groups 
'CowColour Brown' -match '(?<Attribute>\w+) (?<Value>\w+)' | out-null $matches.Attribute $matches.Value 
#cowColour 
#Brown

#Matching groups - your $matches object will have properties containing the valid matches 
"Subnet:10.1.1.0/24" -match 'Subnet:(?<SiteSubnet>(?:\d{1,3}\.){3}\d{1,3}/\d+)'

#Replace to reformat a string 
'This is a wild test' -replace '.*(w[^ ]+).*','Not so $1' 
#Not so wild

#Lazy matching (to prevent over-matching) use a ? after the + or * 
"<h1>MyHeading</h1>" -replace '<([^/]+?)>','<cow>' -replace '</([^/]+?)>','</cow>' 
#<cow>MyHeading</cow>

#negative lookbehind 
($DistinguishedName -split '(?<!\\),')[1..100] -join ','