Ezine 172 - Getting Started with Microsoft PowerShell
Ezine 172 - Getting Started with Microsoft PowerShell
I have designed this week's ezine for those who are new to PowerShell.
It is also aimed at those who have had one flirtation with this scripting
language, and are now returning for a second romance. For those who have followed my previous
scripts I say to
them, 'Focus on the Learning Notes in the examples below'.
Topics for Getting Started with PowerShell
Even though Microsoft make their help files comprehensive, even though the
internet has a vast source of information, people are still reluctant to
take advantage of this help. I am convinced that the root
cause of this avoidance is now psychological rather than any inadequacy of the
help files. Asking for help seems to have a stigma, particularly for
men. Perhaps my expressing this view will spur people to take the contrary
view, and as a result they will seek help at every opportunity - just to
prove me wrong!
With learning PowerShell I have performed the mental trick of 'seeking assistance'
rather than 'pleading for help'. Here are five techniques that served me
well in getting started with PowerShell, this week I will concentrate on
item #2. get-Command.
- Read the screen. Examine each PowerShell error message, in
particular, note the line number.
- get-Command. What cmdlets are out there?
- get-Help verb-Noun -full. This gives detailed assistance with the parameters,
and good examples of the cmdlet in use.
- get-Member. This displays properties which we can then employ
in making better scripts.
- get-Help about* Please note there is a little known family of
help files beginning with 'About_'.
This week I want to feature a technique which lists all the built-in PowerShell
cmdlets. From this simple beginning, we will move on to investigating processes currently
running on your computer. I have twin aims of introducing you to get-Command, and
then doing some real work with get-Process.
Preparation: Install Microsoft PowerShell
Overview
I am assuming that you have installed
PowerShell, and you are sitting at the PowerShell prompt. If you don't
yet have PowerShell then downloaded the appropriate version of PowerShell and
of .Net Framework
from Microsoft's site.
Detailed instructions
For detailed instruction on getting PowerShell up and running
see the previous ezine.
Always remember that each PowerShell cmdlet consist of a verb-Noun couplet. All that get-Command does is let you know which PowerShell cmdlets
exist and are
available. A simple reason for researching with this command is that I cannot remember
the names of all the objects that go with the 'get' verb. A more advanced
reason for employing get-Command, I don't know what commands are available after I add a PowerShell snap-in such as QAD cmdlets.
For a basic form of this example, just type these three words:
get-Command get*
# PowerShell script to research
Microsoft PowerShell commands
# Author: Guy Thomas
# Version 1.2 September 2008 tested on PowerShell v 1.0
$Research = get-Command get*
$Research
"There are " + $Research.count
+ " commands beginning with get"
Learning Points
Note 1: Introducing the variable $Research is not
strictly necessary, however, it increases our capability and knowledge by
exposing the .count property.
Note 2: Observe how flexible the plus sign is.
Not only does (+) add numbers, but also it joins text strings.
Incidentally, I once spent ages looking for PowerShell's concatenator, when
all I needed was (+).
Note 3: 'Get' is the default action of every PowerShell
cmdlet. By that I mean you could try plain 'Command' instead of
'get-Command'. It is also no surprise that you see more cmdlets
beginning with 'get' than other verb. Furthermore, 'get' is safer to
experiment with than 'set', 'remove', or 'stop'.
Challenge: Seek out other PowerShell commands, for
instance instead of get*, substitute: start*, new*, or any of the verbs
mentioned in Note 3.
Calculating IP Address
ranges is a black art, which many network managers solve by creating custom
Excel spreadsheets. IPAT cracks this problem of allocating IP addresses
in networks in two ways:
For Mr Organized there is a nifty subnet
calculator, you enter the network address and the subnet mask, then IPAT
works out the usable addresses and their ranges.
For Mr Lazy IPAT
discovers and then displays the IP addresses of existing computers.
Download the Free IP Address Tracker
Please excuse the jump from help techniques with get-Command to get-Process, but I am keen
to show you scripts that perform real tasks. One theme that I keep
revisiting is how
PowerShell scripts mimic what you can do with a GUI. Take every
opportunity to compare the GUI with the script, and thus discover a little more
about the operating system, while you learn about PowerShell.
Scripts are usually superior to the GUI particularly when it comes to repetitive tasks. In the case of the Task Manager and its
Process tab, you can also do stuff with PowerShell that I have not found a way of
achieving with the GUI.
This script groups 'Processes' by their PriorityClass. Thus any
unknown program in the High, or AboveNormal group, maybe a rogue process,
or at least one worth investigating.
Real Life Mission: To group processes by their PriorityClass or Company name,
incidentally, I cannot display this company information with Task Manager.
Purely PowerShell Missions: To introduce the pipeline | and to introduce
group-Object
# PowerShell script to list
processes grouped by Priority Class
# Author: Guy Thomas
# Version 1.2 August 2008 tested on PowerShell v 1.0
get-Process | group-Object -property PriorityClass
Learning Points
Note 1: The pipeline (|) is a famous PowerShell technique
for pumping the output of the first command (get-Process) into the second clause
(group-Object).
Note 2: The simplest form of this command is plain
get-Process.
Note 3: To apply what we learned in Example 1, and
to count the processes try:
$Proc = get-Process
$Proc; "The number of processes is : " + $Proc.count
This cmdlet will list your processes grouped by their company name.
# PowerShell script to list
processes grouped by Company
# Author: Guy Thomas
# Version 1.2 August 2008 tested on PowerShell v 1.0
get-Process | group Company
Note 1: The verb 'group' is only ever associated
with one noun called 'Object'. Thus you can omit the (-Object) part and
PowerShell will deduce that there is only one meaning and so run the
truncated command, group Company.
Note 2: group-Object expects a property in
position one, directly after the command, thus you can omit the -property
parameter and PowerShell will 'assume' that company is a property.
If you are looking for handy network utilities, try some of the free downloads at
Tools4Ever
Summary of Getting Started with Microsoft PowerShell
There are 5 techniques for getting self-help with Microsoft PowerShell.
Sometimes when I am trying to develop a script it does not produce the
output that I want. At this point I realize
that I a different command could produce better results. This
week we have listed the available cmdlets with get-Command. Next week
we will investigate the operating system's event logs.
If you like this page then please share it with your friends
See more Microsoft PowerShell tutorials
• PowerShell Tutorials •
Methods • Cmdlets
• PS Snapin •
Profile.ps1 • Exchange 2007
•
Command & Expression Mode •
PowerShell pipeline (|) •
PowerShell 'where' •
PowerShell 'Sort'
If you see an error of any kind, do let me know. Please report any factual mistakes, grammatical errors or broken links, I will be happy to not only to correct the fault, but also to give you credit.
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