Powershell

Powershell Tutorial is available at http://www.powershellpro.com/powershell-tutorial-introduction/

How to Write a PowerShell Script
Reference : http://www.suite101.com/content/how-to-write-a-powershell-script-a115669

There are no restrictions as to where the scripts are placed on the computer, but they must always have the same file name extension - .ps1.

An Example PowerShell Script

The best way to learn about scripting is to examine a real example, in this case a script that will:

• list all running processes that are using more that 1M of memory
• ignore the PowerShell process
• sort the result
• place the result in a file formatted for viewing on a web site

The script is quite simple, although it is worth noting the use of pipes (represented by |). Pipes allow the output of one Cmdlet to be used as the input to another:

get-process |

where-object {$_.WS -ge 1048576} |

where-object {$_.processname -ne "powershell"} |

sort-object WS –descending |

convertto-html -property Name,WS > c:\Inetpub\wwwroot\ps.html

If this script is saved to “c:\powershell\check_memory.ps1” then it can be run from the command prompt by typing:

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powershell c:\powershell\check_memory

However, life is never quite that simple.

Enabling PowerShell Scripts

Anyone running a PowerShell at this point will probably receive an error something like:

File c:\powershell\check_memory.ps1 cannot be loaded because the execution of scripts is disabled on this system. Please see "get-help about_signing" for more details.

At line:1 char:26

+ c:\powershell\check_memory <<<<

That’s because PowerShell does not automatically allow scripts. It actually has four levels of security (known as execution policies):

• Restricted: This is the default execution policy, and stops all scripts from running
• AllSigned: Allows scripts to run, but only if they have an associated digital signature from a trusted publisher.
• RemoteSigned: Allows all scripts on the computer to run and any other scripts that have an associated digital signature from a trusted publisher
• Unrestricted: Allows all scripts to run (but this should be avoided)

The current execution policy can be examined from the command prompted:

powershell get-executionpolicy

It will, in all likelihood, return “Restricted”. It’s then just a matter of setting the execution policy to be less restrictive:

powershell set-executionpolicy RemoteSigned

The script can now be run and the results examined in the HTML file that it produces.


Read more at Suite101: How to Write a PowerShell Script: An Introduction to Automating PowerShell http://www.suite101.com/content/how-to-write-a-powershell-script-a115669#ixzz11gSjWgZD