How to Grep in PowerShell:

Applies To : PowerShell

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For those who have lived in the Linux/Unix command line, the ‘grep‘ command is a commonly used way of finding something that you want in a chunk of data.

Øyvind Kallstad did a great writeup of comparing a bunch of ways to use PowerShell instead of grep which is worth reading.

The article covers a bunch of scenarios, and is centered around starting with the ‘grep’ command and working with it. However, there’s the other common use case of running a different command, then piping those results to grep to search for something.

This blogpost was triggered by Janet who asked me this fair question:

https://twitter.com/missjte/status/834132904045342720

https://twitter.com/missjte/status/834133021829664770

As with poor cute cats, there’s more than one way to skin PowerShell.

I had to do some research and asking around on this, because normally I’d filter out the property of the object I was looking at, and work with that. Using the get-process example:

get-process | where ProcessName -like "*foo*

That works, but it’s still a lot clunkier than what a grep user would expect. An easier way would be to use the ‘findstr‘ program (which also has a bunch of useful swtiches):

get-process | findstr foo

I say program because ‘findstr’ is not a PowerShell cmdlet, but it’s still native to Windows and works perfectly fine. It’s case sensitive though, so you need to use -i for case insensitive results.

That’s great for simple stuff, but we’re sort of breaking what PowerShell does. You’re no longer dealing with a standard PowerShell object, so further piping and processing won’t really work.

The ‘proper’ PowerShell way would be to use the ‘Where-Object’ command:

Get-Process | Where-Object {$_ | Select-String "foo"}

A bit longer, but you can shorten ‘Where-Object’ to ‘Where’. Although more involved, it’s good to get into the habit of doing it this way, so when you’re piping this to the next command, it still says as a standard object that can be read and manipulated.’

(Update 24th Feb 2017) As Steve_N points out in the comments section, there’s a much shorter way of doing this:

ps *foo*

That’s it. Many PowerShell commands have inbuilt aliases, including ‘get-process’. You can see what this is with the command ‘get-alias -definition get-process’

This shows that ‘gps’ and ‘ps’ are both aliases to the command  ‘get-process’. You can also create your own aliases with the ‘set-alias‘ command.

The ‘*foo*’ part works because the command assumes the -name switch has been used, which lets you define what criteria to search and show in the ProcessName field. This is the same way that many commands don’t need the -identity switch used, because it’s written to assume you’re going to tell it what identity/username/upn to work with.

This can also be piped to something else, so it’s a winner. It’s less ideal for scripts though, because it’s much harder to read, and you can’t assume that everyone will know the short alias of a full command.

Also note that this isn’t grep related at all, so part of the answer to the original question is that you may not even need grep or select-string as it adds unnecessary overhead of getting data and parsing it, whereas this updated example filters the data as it’s obtained.

(Update ends)

PowerShell isn’t a Linux/Unix command line, but Microsoft have incorporated many of the concepts from bash. If you still can’t bear to use PowerShell on Windows, there’s always the Linux Bash Shell on Windows.

Thanks again to Steve Mclnerey for the grep advice :)