# Introduction to PowerShell for Unix People The point of this section is to outline a few areas which I think \*nix people should pay particular attention to when learning Powershell. ## Resources for learning PowerShell A *full* introduction to PowerShell is beyond the scope of this e-book. My recommendations for an end-to-end view of PowerShell are: * [Learn Windows PowerShell in a Month of Lunches](http://www.manning.com/jones3/) - Written by powershell.org's Don Jones and Jeffery Hicks, I would guess that this is the book that most people have used to learn Powershell. * Microsoft Virtual Academy's two PowerShell 'Jump Start' videos [Getting Started with PowerShell](http://www.microsoftvirtualacademy.com/training-courses/getting-started-with-powershell-3-0-jump-start) and [Advanced Tools & Scripting with PowerShell](http://www.microsoftvirtualacademy.com/training-courses/advanced-tools-scripting-with-powershell-3-0-jump-start) ## unix-like aliases PowerShell is a friendly environment for Unix people to work in. Many of the concepts are similar, and the PowerShell team have built in a number of Powershell aliases that look like unix commands. So, you can, for example type: ``` ls ``` ....and get this: ``` Directory: C:\temp Mode LastWriteTime Length Name ---- ------------- ------ ---- -a--- 22/02/2015 16:51 25773 all_the_details.md -a--- 20/02/2015 07:31 3390 commands-summary.md ``` These can be quite useful when you're switching between shells, although I found that it can be irritating when the 'muscle-memory' kicks in and you find yourself typing `ls -ltr` in PowerShell and get an error. ## the pipeline The PowerShell pipeline is much the same as the Bash shell pipeline. The output of one command is piped to another one with the '`|`' symbol. The big difference between piping in the two shells is that in the unix shells you are piping *text*, whereas in PowerShell you are piping *objects*. This sounds like it's going to be a big deal, but it's not really. In practice, if you wanted to get a list of process names, in bash you might do this: ``` ps -ef | cut -c 49-70 ``` ...whereas In PowerShell you would do this: ``` get-process | select ProcessName ``` In Bash you are working with characters, or tab-delimited fields. In PowerShell you work with field names, which are known as 'properties'. You can determine the properties of a Powershell object with the command `get-member` ## get-help, get-command, get-member ### get-member When you run a PowerShell command, such as `get-history` only a subset of the `get-history` output is returned to the screen. In the case of `get-history`, by default two properties are shown - 'Id' and 'Commandline'... ``` $ get-history Id CommandLine -- ----------- 1 dir -recurse c:\temp ``` ...but get-history has 4 other properties which you might or might not be interested in: ``` $ get-history | select * Id : 1 CommandLine : dir -recurse c:\temp ExecutionStatus : Completed StartExecutionTime : 06/05/2015 13:46:56 EndExecutionTime : 06/05/2015 13:47:07 ``` The disparity between what is shown and what is available is even greater for more complex entities like 'process'. By default, on my screen, `get-process` shows 8 columns, but there are actually over 50 properties (as well as 20 or so methods) available. The full range of what you can return from a PowerShell command is given by the `get-member` command\[2]. To run `get-member`, you pipe the output of the command you're interested in to it, for example: ``` get-process | get-member ``` ....or, more typically: ``` get-process | gm ``` `get-member` is one of the 'trinity' of 'help'-ful commands: * get-member * get-help * get-command ### get-help `get-help` is similar to the Unix `man`\[3]. So if you type `get-help get-process`, you'll get this: ``` NAME Get-Process SYNOPSIS Gets the processes that are running on the local computer or a remote computer. SYNTAX Get-Process [[-Name] ] [-ComputerName ] [-FileVersionInfo] [-Module] [] Get-Process [-ComputerName ] [-FileVersionInfo] [-Module] -Id [] Get-Process [-ComputerName ] [-FileVersionInfo] [-Module] -InputObject [] DESCRIPTION The Get-Process cmdlet gets the processes on a local or remote computer. Without parameters, Get-Process gets all of the processes on the local computer. You can also specify a particular process by process name or process ID (PID) or pass a process object through the pipeline to Get-Process. By default, Get-Process returns a process object that has detailed information about the process and supports methods that let you start and stop the process. You can also use the parameters of Get-Process to get file version information for the program that runs in the process and to get the modules that the process loaded. RELATED LINKS Online Version: http://go.microsoft.com/fwlink/?LinkID=113324 Debug-Process Get-Process Start-Process Stop-Process Wait-Process REMARKS To see the examples, type: "get-help Get-Process -examples". For more information, type: "get-help Get-Process -detailed". For technical information, type: "get-help Get-Process -full". For online help, type: "get-help Get-Process -online" ``` There are a couple of wrinkles which actually make the PowerShell 'help' even more *help*-ful. * you get basic help by typing `get-help`, more help by typing `get-help -full` and...probably the best bit as far as I'm concerned...you can cut to the chase by typing `get-help -examples` * there are lots of '`about_`' pages. These cover concepts, new features (in for example `about_Windows_Powershell_5.0`) and subjects which dont just relate to one particular command. You can see a full list of the 'about' topics by typing `get-help about` * get-help works like `man -k` or `apropos`. If you're not sure of the command you want to see help on, just type `help process` and you'll see a list of all the help topics that talk about processes. If there was only one it would just show you that topic * Comment-based help. When you write your own commands you can (and should!) use the comment-based help functionality. You follow a loose template for writing a comment header block, and then this becomes part of the get-help subsystem. It's good. ### get-command If you don't want to go through the help system, and you're not sure what command you need, you can use `get-command`. I use this most often with wild-cards either to explore what's available or to check on spelling. For example, I tend to need to look up the spelling of `ConvertTo-Csv` on a fairly regular basis. PowerShell commands have a very good, very intuitive naming convention of a verb followed by a noun (for example, `get-process`, `invoke-webrequest`), but I'm never quite sure where 'to' and 'from' go for the conversion commands. To quickly look it up I can type: `get-command *csv*` ... which returns: ``` $ get-command *csv* CommandType Name ModuleName ----------- ---- ---------- Alias epcsv -> Export-Csv Alias ipcsv -> Import-Csv Cmdlet ConvertFrom-Csv Microsoft.PowerShell.Utility Cmdlet ConvertTo-Csv Microsoft.PowerShell.Utility Cmdlet Export-Csv Microsoft.PowerShell.Utility Cmdlet Import-Csv Microsoft.PowerShell.Utility Application ucsvc.exe Application vmicsvc.exe ``` ## Functions Typically PowerShell coding is done in the form of *functions*\[4]. What you do to code and write a function is this: Create a function in a plain text .ps1 file\[5] ``` gvim say-HelloWorld.ps1 ``` ![say-helloworld.png](https://github.com/devops-collective-inc/unix-persons-guide-to-powershell/tree/880be7ecc8a6345a2406f5e528bbd4e5f9d8c91f/manuscript/images/say-helloworld.png) ...then source the function when they need it ``` $ . .\say-HelloWorld.ps1 ``` ...then run it ``` $ say-helloworld Hello, World ``` Often people autoload their functions in their `$profile` or other startup script, as follows: ``` write-verbose "About to load functions" foreach ($FUNC in $(dir $FUNCTION_DIR\*.ps1)) { write-verbose "Loading $FUNC.... " . $FUNC.FullName } ``` ## Footnotes \[1] If you wanted the equivalent of `ls -ltr` you would use `gci | sort lastwritetime`. 'gci' is an alias for 'get-childitem', 'sort' is an alias for 'sort-object'. \[2] Another way of returning all of the properties of an object is to use 'select \*'...so in this case you could type `get-process | select *` \[3] There is actually a built-in alias `man` which tranlates to `get-help`, so you can just type `man` if you're pining for Unix. \[4] See the following for more detail on writing functions rather than scripts: \[5] I'm using 'gvim' here, but notepad would work just as well. PowerShell has a free 'scripting environment' called *PowerShell ISE*, but you don't have to use it if you dont want to.