Windows PowerShell Language Quick Reference

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

+ addition, concatenation - Subtraction * multiplication, string repetition / Division % Modulus

Array Operations

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

Arrays

“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.

Assignment Operators

=, +=, -=, *=, /=, %=

Associative Arrays (Hashtables)

$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

Boolean Values and Operators

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

Break (Scripting)

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; }

Command Expansion Operators

$( ) 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

Comments

# 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

Comparison Operators

-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 )

Continue (Scripting)

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.

Dot Sourcing

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

Escape Sequences

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)

Execution Order

Windows PowerShell attempts to resolve commands in the following order: aliases, functions, cmdlets, scripts, executables, and normal files.

For (Scripting)

[:label] for ([initializer]; [condition]; [iterator]) {}   Example: for ($i = 0; $i –lt 5; $i++) {Write-Object $i}

Foreach (Scripting)

[: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”}}

Functions (Scripting)

function MyFunction {       write-object $args[0] }   function test ([string]$label=”default label”,[int]$start=0) { BEGIN {$x=$start} PROCESS {“$label: $_”’; $x++}      END{“$x total”} }

Filters (Scripting)