Powershell

Powershell

Windows Powershell is a shell / scripting environment created by Microsoft. You can read more about the technical stuff here. This page serves as not a complete description of Powershell or its history, but a guide on how to use it. Some programming knowledge is expected but not absolutely required. Experience with bash is also probably helpful, but you could learn something even if you have zero experience with any kind of shell or scripting environment.

Rationale

I think Powershell is pretty neat. I used Linux as my main OS for about 5 years and had to switch to Windows very recently for a myriad of reasons. Ironically I might have to switch back soon (taking a *NIX Systems Programming class), but in the meantime I wanted a scripting language for Windows that was better for the everyday grind than Python, so I did some research and found Powershell. Its no bash, but its close, and I think if it was embraced by the world and the Internet (re: people give M$ a reason to care about it) then it could be really great. The fact that Microsoft is actively trying to make Windows a more dev-friendly environment shows that exciting things are happening (See: SSH on Windows), and I believe those changes will start begin with the upcoming changes to Powershell in Windows 10.

- Anon, June 9th 2015

Getting Started

Here is a chart that I made. File:PsQuickReference-20150609.pdf (I made it as a .pdf because I can't be assed to learn how to use WikiMedia properly, so if you don't like that please contribute yourself.) It was designed to get someone familiar with the *NIX shell up and scripting as fast as possible, and includes all the common commands I remember using often on *NIX.

Let's do a quick analysis of this chart and come up with some pros and cons.

Pros of Powershell:

• Syntax is sometimes much clearer than bash. Powershell's syntax is also much more consistent. This makes it much easier to compose and read scripts.
• Syntax is generally not case sensitive. Some people might put this as a con but I like it and I think many others do too.
• Familiar conventions to get *NIX people started, such as $ for variables, cp, mv, mkdir, etc.
• Familiar object-oriented conventions are baked in. If you come from a Java, C#, or even Ruby background, lots of things should feel familiar.
• Decently fast, both performance-wise and to learn.
• .NET environment, meaning its extensible with your own .NET objects. * Lots of juicy default aliases for juicy shortcuts. You can tell whoever wrote this shit actually uses a shell.
• Access to lots of Windows APIs/features such as the registry and Internet Explorer.
• Powershell Community Extensions and/or PsGet.
• Its not cmd.exe ! ! !

Cons of Powershell:

• Windows only, whereas bash or sh is on basically every OS (including Windows with Cygwin).
• Cannot run scripts by default, and Powershell only comes by default with Win7 and up. Makes scripts unportable because they are not necessarily guarunteed to run on another machine.
• Sometimes the commands are quite verbose. It can be especially annoying to type out very verbose arguments, such as '-Recurse' as opposed to '-r'.
• Fairly slow autocomplete (hopefully will be fixed in Windows 10).
• No reverse i-search by default.
• Capitals everywhere. Why? I know it usually doesn't matter but its still kind of ugly.
• Binary logs (Get-History is an example, I think).

Initial Configuration

First thing you're gonna wanna do is fix Microsoft's idiocy and make scripts executable. To do that, run this command:

   Set-ExecutionPolicy -CurrentUser RemoteSigned

You might need to do it in an elevated prompt. To do that, open the Start Menu, type 'Windows Powershell', right-click the link, and select 'Run as Administrator'. Then enter the command.

Next, you'll probably want a config file to store custom aliases, functions, and the like. To do this, run this little snippet:

   if ( -Not (Test-Path $profile)) {
       New-Item -Type File $profile
   }
   Notepad $profile

This will be where you store your customized Powershell configuration.

Some Helpful Default Aliases

Here are some useful aliases that are baked into Powershell. You'll probably find yourself using them often, and they may seem familiar, so take a good, long look.

   CommandType     Name
   -----------     ----
   Alias           % -> ForEach-Object
   Alias           % -> ForEach-Object
   Alias           ? -> Where-Object
   Alias           h -> Get-History
   Alias           r -> Invoke-History
   Alias           ac -> Add-Content
   Alias           cd -> Set-Location
   Alias           compare -> Compare-Object
   Alias           cp -> Copy-Item
   Alias           curl -> Invoke-WebRequest
   Alias           diff -> Compare-Object
   Alias           foreach -> ForEach-Object
   Alias           ft -> Format-Table
   Alias           fw -> Format-Wide
   Alias           gc -> Get-Content
   Alias           kill -> Stop-Process
   Alias           ls -> Get-ChildItem
   Alias           man -> help
   Alias           measure -> Measure-Object
   Alias           nal -> New-Alias
   Alias           nv -> New-Variable
   Alias           ps -> Get-Process
   Alias           pwd -> Get-Location
   Alias           r -> Invoke-History
   Alias           ren -> Rename-Item
   Alias           rm -> Remove-Item
   Alias           rmdir -> Remove-Item
   Alias           rv -> Remove-Variable
   Alias           sc -> Set-Content
   Alias           select -> Select-Object
   Alias           sort -> Sort-Object
   Alias           start -> Start-Process
   Alias           sv -> Set-Variable
   Alias           tee -> Tee-Object
   Alias           type -> Get-Content
   Alias           wget -> Invoke-WebRequest
   Alias           where -> Where-Object

Getting Help

As you can see above, man is an alias for a command called Get-Help. It does exactly what you think it does.

   PS C:\> get-help get-help
   
   NAME
       Get-Help
   
   SYNTAX
       Get-Help [[-Name] <string>] [-Path <string>] [-Category <string[]> {Alias | Cmdlet | Provider | General | FAQ
       | Glossary | HelpFile | ScriptCommand | Function | Filter | ExternalScript | All | DefaultHelp | Workflow}]
       [-Component <string[]>] [-Functionality <string[]>] [-Role <string[]>] [-Full]  [<CommonParameters>]
   
       Get-Help [[-Name] <string>] -Detailed [-Path <string>] [-Category <string[]> {Alias | Cmdlet | Provider |
       General | FAQ | Glossary | HelpFile | ScriptCommand | Function | Filter | ExternalScript | All | DefaultHelp |
       Workflow}] [-Component <string[]>] [-Functionality <string[]>] [-Role <string[]>]  [<CommonParameters>]
   
       Get-Help [[-Name] <string>] -Examples [-Path <string>] [-Category <string[]> {Alias | Cmdlet | Provider |
       General | FAQ | Glossary | HelpFile | ScriptCommand | Function | Filter | ExternalScript | All | DefaultHelp |
       Workflow}] [-Component <string[]>] [-Functionality <string[]>] [-Role <string[]>]  [<CommonParameters>]
   
       Get-Help [[-Name] <string>] -Parameter <string> [-Path <string>] [-Category <string[]> {Alias | Cmdlet |
       Provider | General | FAQ | Glossary | HelpFile | ScriptCommand | Function | Filter | ExternalScript | All |
       DefaultHelp | Workflow}] [-Component <string[]>] [-Functionality <string[]>] [-Role <string[]>]
       [<CommonParameters>]
   
       Get-Help [[-Name] <string>] -Online [-Path <string>] [-Category <string[]> {Alias | Cmdlet | Provider |
       General | FAQ | Glossary | HelpFile | ScriptCommand | Function | Filter | ExternalScript | All | DefaultHelp |
       Workflow}] [-Component <string[]>] [-Functionality <string[]>] [-Role <string[]>]  [<CommonParameters>]
   
       Get-Help [[-Name] <string>] -ShowWindow [-Path <string>] [-Category <string[]> {Alias | Cmdlet | Provider |
       General | FAQ | Glossary | HelpFile | ScriptCommand | Function | Filter | ExternalScript | All | DefaultHelp |
       Workflow}] [-Component <string[]>] [-Functionality <string[]>] [-Role <string[]>]  [<CommonParameters>]
   
   ALIASES
       None
   
   REMARKS
       Get-Help cannot find the Help files for this cmdlet on this computer. It is displaying only partial help.
           -- To download and install Help files for the module that includes this cmdlet, use Update-Help.
           -- To view the Help topic for this cmdlet online, type: "Get-Help Get-Help -Online" or
              go to http://go.microsoft.com/fwlink/?LinkID=113316.

Get-Help works with any command and any alias. Some useful parameters to Get-Help are -Online and -ShowWindow for the GUI babbies and -Example for hands-on learners.

If you notice in the 'Remarks' section, Powershell has the unhelpful feature of not actually coming with complete documentation. To fix this, use the cmdlet Update-Help, either standalone or with a cmdlet passed as a parameter, to download the online help files to your local machine.

Another great tool for getting help is Get-Member. Unsure of how to use an object? Piping it to Get-Member will display all the object's data members and methods so that you can find and use the one you want.

   PS C:\> "abcd" | get-member
   
   
      TypeName: System.String
   
   Name             MemberType            Definition
   ----             ----------            ----------
   Clone            Method                System.Object Clone(), System.Object ICloneable.Clone()
   CompareTo        Method                int CompareTo(System.Object value), int CompareTo(string strB), int IComp... Contains         Method                bool Contains(string value)
   CopyTo           Method                void CopyTo(int sourceIndex, char[] destination, int destinationIndex, in... EndsWith         Method                bool EndsWith(string value), bool EndsWith(string value, System.StringCom... Equals           Method                bool Equals(System.Object obj), bool Equals(string value), bool Equals(st... GetEnumerator    Method                System.CharEnumerator GetEnumerator(), System.Collections.Generic.IEnumer... GetHashCode      Method                int GetHashCode()
   GetType          Method                type GetType()
   GetTypeCode      Method                System.TypeCode GetTypeCode(), System.TypeCode IConvertible.GetTypeCode()
   IndexOf          Method                int IndexOf(char value), int IndexOf(char value, int startIndex), int Ind... IndexOfAny       Method                int IndexOfAny(char[] anyOf), int IndexOfAny(char[] anyOf, int startIndex... Insert           Method                string Insert(int startIndex, string value)
   IsNormalized     Method                bool IsNormalized(), bool IsNormalized(System.Text.NormalizationForm norm... LastIndexOf      Method                int LastIndexOf(char value), int LastIndexOf(char value, int startIndex),... LastIndexOfAny   Method                int LastIndexOfAny(char[] anyOf), int LastIndexOfAny(char[] anyOf, int st... Normalize        Method                string Normalize(), string Normalize(System.Text.NormalizationForm normal... PadLeft          Method                string PadLeft(int totalWidth), string PadLeft(int totalWidth, char paddi... PadRight         Method                string PadRight(int totalWidth), string PadRight(int totalWidth, char pad... Remove           Method                string Remove(int startIndex, int count), string Remove(int startIndex)
   Replace          Method                string Replace(char oldChar, char newChar), string Replace(string oldValu... Split            Method                string[] Split(Params char[] separator), string[] Split(char[] separator,... StartsWith       Method                bool StartsWith(string value), bool StartsWith(string value, System.Strin... Substring        Method                string Substring(int startIndex), string Substring(int startIndex, int le... ToBoolean        Method                bool IConvertible.ToBoolean(System.IFormatProvider provider)
   ToByte           Method                byte IConvertible.ToByte(System.IFormatProvider provider)
   ...

Scripting Stuff

Variables and Data Types

Powershell has lots of weird types (hell, everything is an object), but primitives are pretty tame, and work as expected.

   PS C:\> $a = 1
   PS C:\> $a++
   PS C:\> echo $a
   2
   PS C:\> 1 + 3 / 2
   2.5
   PS C:\> (1+3)/2
   2
   PS C:\> 4 % 2
   0
   PS C:\>

Strings work pretty much exactly like in Java. The backtick (`) is used for escapes, you can compare and concatenate strings, search within them, the list goes on.

   PS C:\> $a = "Hello World!"
   PS C:\> echo $a
   Hello World!
   PS C:\> $a = "Hello `n World!"
   PS C:\> echo $a
   Hello
    World!
   PS C:\> $a = "Hello`t`tWorld!"
   PS C:\> $a
   Hello           World!
   PS C:\> $a = "Hello ``World``!"
   PS C:\> $a
   Hello `World`!
   PS C:\> echo "`$"
   $

   PS C:\> $a = "Hello ``World``!"
   PS C:\> $a.contains("ello")
   True
   PS C:\> $a.startswith("He")
   True
   PS C:\> $a.endswith("!")
   True

   PS C:\> $a = "Hello ``World``!"
   PS C:\> $a + "`n`t- Babbies first words" # Concatenation!
   Hello `World`!
           - Babbies first words
   PS C:\> $a.CompareTo("Hello")
   1
   PS C:\> $a.CompareTo("ZZZZZ")
   -1
   PS C:\> $a.CompareTo($a)
   0
   PS C:\> $a.indexof("W")
   7

Arrays are declared either purely with commas or with the @( ) syntax, and can contain mixed types.

   PS C:\> $a = $(1, 2, 3, 4)
   PS C:\> $a = 1,2,3,4
   PS C:\> $a = "a",1,"b",2
   PS C:\> $a.Length
   4

They can also be indexed as you would expect and sliced with ranges:

   PS C:\> $a[0]
   a
   PS C:\> $a[1..2]
   1
   b

Hash tables, or dictionaries, are also implemented in Powershell, and work similarly to arrays and dictionaries in other languages:

   PS C:\> $a = @{Key1=1;Key2=2;Key3="YourName"}
   PS C:\> $a["Key1"] + 2
   3
   PS C:\> $a["Key3"] + "IsBob"
   YourNameIsBob
   PS C:\>

Most everything implements .getType():

   PS C:\> $a = "asdf"
   PS C:\> $a.getType()
   
   IsPublic IsSerial Name                                     BaseType
   -------- -------- ----                                     --------
   True     True     String                                   System.Object
   
   
   PS C:\> (1).getType()
   
   IsPublic IsSerial Name                                     BaseType
   -------- -------- ----                                     --------
   True     True     Int32                                    System.ValueType
   
   
   PS C:\> ("asdf").getType()
   
   IsPublic IsSerial Name                                     BaseType
   -------- -------- ----                                     --------
   True     True     String                                   System.Object
   
   
   PS C:\> (@{}).getType()
   
   IsPublic IsSerial Name                                     BaseType
   -------- -------- ----                                     --------
   True     True     Hashtable                                System.Object

and types can be casted and declared with square brackets.

   PS C:\> [int32]$i = 40;
   PS C:\> [int32]$j = "asdf";
   Cannot convert value "asdf" to type "System.Int32". Error: "Input string was not in a correct format."
   At line:1 char:1
   + [int32]$j = "asdf";
   + 22:19, 9 June 2015 (EDT)22:19, 9 June 2015 (EDT)22:19, 9 June 2015 (EDT)Hevnoraak (talk)
       + CategoryInfo          : MetadataError: (:) [], ArgumentTransformationMetadataException
       + FullyQualifiedErrorId : RuntimeException
   PS C:\> [int32](0.0001)
   0
   PS C:\>

Working with Data

Format Commands

Powershell provides several commands for changing the way that it displays data within the shell.

   PS C:\> get-command | ? { $_.Verb -eq "Format" -and $_.ModuleName -eq "Microsoft.Powershell.Utility" }
   
   CommandType     Name                                               ModuleName
   -----------     ----                                               ----------
   Cmdlet          Format-Custom                                      Microsoft.PowerShell.Utility
   Cmdlet          Format-List                                        Microsoft.PowerShell.Utility
   Cmdlet          Format-Table                                       Microsoft.PowerShell.Utility
   Cmdlet          Format-Wide                                        Microsoft.PowerShell.Utility

For now I'm only going to cover Format-Table, Format-Wide, and Format-List.

Format-Table

Running Format-Table on just about anything will produce results which look familiar. I'm not 100% sure about this (need to find a source), but I'm pretty sure Powershell runs every object that goes into stdout through Format-Table before printing it. So just the cmdlet standalone will give you nothing; its the parameters that go into making the magic happen. Look at this example, taken [https://technet.microsoft.com/en-us/library/ee692794.aspx | straight from the horse's mouth]:

   PS C:\> $a = @{Expression={$_.Name};Label="Process Name";width=25}, `
   >>> @{Expression={$_.ID};Label="Process ID";width=15}, `
   >>> @{Expression={$_.MainWindowTitle};Label="Window Title";width=40}

   PS C:\> Get-Process | Format-Table $a

   Process Name                   Process ID Window Title
   ------------                   ---------- ------------
   lsass                                1284
   LSSrvc                               2112
   MDM                                  2240
   notepad                              2348 Untitled - Notepad
   notepad                              3944 Untitled - Notepad
   OUTLOOK                              1192 Inbox - Microsoft Outlook
   powershell                           1348 Script Center

The assignment to $a looks incredibly confusing until you realize that @{} is how Powershell does hash tables and/or dictionaries, and that arrays are defined simply with commas. (Read the Variables and Data Types section if you haven't already). Format-Table simply takes in hash tables which describe how each column of the table is going to look with different keys and values inside the hash table.

Format-Wide

The most boring format command: it simply puts the data in multiple columns to make better use of horizontal screen space, like so:

   PS C:\> get-process
   
   Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)     Id ProcessName
   -------  ------    -----      ----- -----   ------     -- -----------
        82       7     1076       4216    44            1672 armsvc
       135       9     5800       8480    39     0.09   5320 audiodg
       316      25    15748      23808   200     6.48   2776 ConEmu
       130      11     2952       6520    91     7.09   3660 ConEmuC64
        51       6      964       4008    49     0.02   4936 conhost
        55       7     1404       4628    50     7.23   5828 conhost
       212      12     1792       3756    44             524 csrss
       180      16     2428      38256   202             600 csrss
       314      17     3880      10912    44            1728 dasHost
   ...

   PS C:\> get-process | format-wide
   
   armsvc                ConEmu
   ConEmuC64             conhost
   conhost               csrss
   csrss                 dasHost
   ....

Note that this seems to kill your use of Select-Object:

   PS C:\> ps | select-object -Property Name,ID,Handles

   Name        Id    Handles
   ----        --    -------
   armsvc    1672         82
   audiodg   5320        126
   ...

   PS C:\> ps | select-object -Property Name,ID,Handles | fw
   
   armsvc                ConEmu
   ConEmuC64             conhost
   conhost               csrss
   csrss                 dasHost
   ...

Format-List

Format-List takes an object or an array of objects and gives a descriptive output of the object's (or objects') properties and values associated with said properties. To be honest, Format-List is kind of a crappy name; the output doesn't really look like a list to me, more like a table. This command is similar to Get-Member but doesn't produce as much output and gives you the data instead of just what data members the object has.

   PS C:\> get-date
  
   Tuesday, June 9, 2015 8:58:23 PM
   
   PS C:\> get-date | format-list
   
   DisplayHint : DateTime
   Date        : 6/9/2015 12:00:00 AM
   Day         : 9
   DayOfWeek   : Tuesday
   DayOfYear   : 160
   Hour        : 20
   Kind        : Local
   Millisecond : 922
   Minute      : 58
   Month       : 6
   Second      : 27
   Ticks       : 635694803079228445
   TimeOfDay   : 20:58:27.9228445
   Year        : 2015
   DateTime    : Tuesday, June 9, 2015 8:58:27 PM

References

• http://www.tomsitpro.com/articles/powershell-variables,2-797.html
• http://softwaresalariman.blogspot.com/2007/12/slicing-powershell-arrays-and-ranges.html