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If you aren’t familiar with sed and grep you may want to stop reading here.

If you are and this is bringing Unix flashbacks, you should read on. I started my career on Unix systems and quickly found that grep and sed were just part of getting the job done and I ended up using them for pretty much everything.

When I started working with PowerShell and I was piping output around I found myself quickly missing good old sed and grep.

As a quick summary, grep just matched something in the text. As an example, directory a file pipe it to grep for part of the name of the file that you were looking for.

Sed provided a way to quickly replace a value within a file with something else (such as replace all instances of XYZCO with ABCCO).

A filter to perform grep

From this blog post I found that you can define a filter which you can then use to perform something like grep. His filter is as follows:

filter grep($keyword) { if ( ($_ | Out-String) -like “*$keyword*”) { $_ } }

Using the blog post concept, I was able to build a similar filter for sed. The following is my filter:

filter sed($before,$after) { %{$_ -replace $before,$after} }

For examples of this let’s start with grep – the PowerShell below lists all services which include the word “Background”

Get-Service | grep Background

grep01.png

 

Or another example of this, listing all SCOM classes which include the word database as shown below (get-scomclass | grep database).

Or a search for all SCOM classes which include “SQL Database” (get-scomclass | grep “SQL database”).

Sed examples

For examples of this let’s go next to sed – the PowerShell below lists all processes and changes the reference to w32time to Timer.

Get-Service | sed w32time Timer

Summary: By putting these filters into the top of my scripts (or using them when I launch PowerShell) I’ve been able to take most of the times where I would need a grep or a sed and utilize this approach to accomplish the same type of functionality.

Additional reference:

http://powershell.com/cs/blogs/tips/archive/2010/06/18/replace-text-in-files.aspx

http://powershell.com/cs/blogs/tips/archive/2011/03/25/filter-powershell-results-fast-and-text-based.aspx

http://blogs.msdn.com/b/zainnab/archive/2007/07/09/grep-and-sed-with-powershell.aspx

http://opensysblog.directorioc.net/2013/03/emulating-sed-command-with-powershell.html

http://pscx.codeplex.com/