Windows PowerShell Language Quick Reference

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Windows PowerShell Language Quick Reference

Native Support for Different Type Systems
Windows PowerShell adapts WMI, XML, ASDI, <city w:st="on"><place w:st="on">ADO</place></city>, and COM objects to provide a common syntax to access their properties and methods.   Example $g = Get-WmiObject Win32_Process $g[0].Name  # instead of $g[0].Properties[“Name”]
Arithmetic Binary Operators
[table]
+	addition, concatenation
-	Subtraction
*	multiplication, string repetition
/	Division
%	Modulus

[/td][/tr][tr][td=1,1,288]Array Operations
[/td][/tr][tr][td=1,1,288]Does this array have a <metricconverter w:st="on" productid="3 in">3 in</metricconverter> it
1,2,3,5,3,2 –contains 3

Return all elements equal to 3:
1,2,3,5,3,2 –eq 3

Return all elements less than 3:
1,2,3,5,3,2 –lt 3

Test if 2 exists in collection:
if (1, 3, 5 –contains 2) …
Other operators:  -gt, -le, -ge, -ne

[/td][/tr][tr][td=1,1,288]Arrays
[/td][/tr][tr][td=1,1,288]

“a”,“b”,”c”	array of strings
1,2,3	array of integers
@()	empty array
@(2)	array of 1 element
1,(2,3),4	array within array
,”hi”	Array of one element
$a[5]	sixth element of array*
$a[2][3]	fourth element or the third
	element of an array
$a[2..20]	Return elements 3 thru 21

·        Arrays are zero based.

[/td][/tr][tr][td=1,1,288]Assignment Operators
[/td][/tr][tr][td=1,1,288]=, +=, -=, *=, /=, %=


[/td][/tr][tr][td=1,1,288]Associative Arrays (Hashtables)
[/td][/tr][tr][td=1,1,288]

$hash = @{ }	Create empty hashtable
$h =@{foo=1;bar=2}	Create and initialize a hashtable
$hash.key1 = 1	Assign 1 to key “key1”
$hash.key1	Returns value of key1
$hash["key1"]	Returns value of key1

[/td][/tr][tr][td=1,1,288]Boolean Values and Operators
[/td][/tr][tr][td=1,1,288]

TRUE	FALSE
$TRUE	$FALSE
Any string of length > 0 except the word “false”	Empty string or the string “false”
Any number !=0	Any number = 0
Array of length > 1	Array of length 0
Array of length 1 whose element is TRUE	Array of length 1 whose element is FALSE
A reference to any object	Null

[/td][/tr][tr][td=1,1,288]Break (Scripting)
[/td][/tr][tr][td=1,1,288]The break commands exits a loop. It can take an optional LABEL to break to
Example:
while (1)
{        $a = something
          if ($a –eq 1) break;
}

[/td][/tr][tr][td=1,1,288]Command Expansion Operators
[/td][/tr][tr][td=1,1,288]

$( )	Returns null
$(1,2,3)	Returns an array containing1,2,3.
$(Get-Alias a*)	Returns evaluation of the expression
@(Get-Alias;Get-Process)	Executes the two commands and returns the results in an array

[/td][/tr][tr][td=1,1,288]Comments
[/td][/tr][tr][td=1,1,288]# This is a comment because # is the first char of a token
$a = “#This is not a comment…”
$a = “something” # …but this is.
Write-Host Hello#world

[/td][/tr][tr][td=1,1,288]Comparison Operators
[/td][/tr][tr][td=1,1,288]

-eq	Equal
-ne	Not equal
-gt –ge	Greater than, greater than or equal to
-lt –le	Less than, less than or equal to

“i” or “c” may be prepended to get case-insensitive or case-sensitive operations (for example, –ceq )
[/td][/tr][tr][td=1,1,288]Continue (Scripting)
[/td][/tr][tr][td=1,1,288]The continue statement continues the next iteration of a loop without breaking out of it. Example:
while (1)
{               $a = something
      if ($a –eq 1) (continue)
      # This line is not reached unless $a == 1
}
#  This line is never reached.
[/td][/tr][tr][td=1,1,288]Dot Sourcing
[/td][/tr][tr][td=1,1,288]Dot sourcing allows running functions, script blocks, and scripts in the current scope rather than a local one. Example:
. MyFunction

If MyFunction sets a variable, it is set in the current scope rather than the function’s local scope.
$a = {$x = Get-Process | Select –First 2}
. $a    #Evaluates the script block in the current scope

[/td][/tr][tr][td=1,1,288]Escape Sequences
[/td][/tr][tr][td=1,1,288]The Windows PowerShell escape character is the backwards apostrophe, or `.  To make a character literal, precede it with `.  To specify a ` use ``.

Special escape sequences
`0	(null)
`a	(alert)
`b	(backspace)
`f	(form feed)
`n	(new line)
`r	(carriage return)
`t	(tab)
`v	(vertical quote)

[/td][/tr][tr][td=1,1,288]Execution Order
[/td][/tr][tr][td=1,1,288]Windows PowerShell attempts to resolve commands in the following order: aliases, functions, cmdlets, scripts, executables, and normal files.

[/td][/tr][tr][td=1,1,288]For (Scripting)
[/td][/tr][tr][td=1,1,288][:label] for ([initializer]; [condition]; [iterator]) {}

Example:
for ($i = 0; $i –lt 5; $i++) {Write-Object $i}

[/td][/tr][tr][td=1,1,288]Foreach (Scripting)
[/td][/tr][tr][td=1,1,288][:label]
foreach (identifier in collection) {}
Expression | foreach {}
Expression | foreach {BEGIN{} PROCESS{} END{}}

Examples:
$i = 1,2,3
foreach ($z in $i) {Write-Object $z}
Get-Process |foreach {BEGIN{$x=1}
       PROCESS{$X++}
       END{“$X Processes”}}

[/td][/tr][tr][td=1,1,288]Functions (Scripting)
[/td][/tr][tr][td=1,1,288]function MyFunction {
      write-object $args[0]
}

function test ([string]$label=”default label”,[int]$start=0)
{ BEGIN {$x=$start} PROCESS {“$label: $_”’; $x++}
     END{“$x total”}
}
[/td][/tr][tr][td=1,1,288]Filters (Scripting)
[/td][/tr][tr][td]padding-right: 5.4pt; border-top: #ece9d8; padding-left: 5.4pt; padding-bottom: 0cm; width: 216pt; padding