Powershell monitor log file for string with select-string and regex

25 April,2017 by Jack Vamvas

Question: I am trying to monitor a log file – used by a third party software. It is a text file where results are dumped if a file transfer is successful. I want to use a powershell script to parse the log file and check if a certain string exists.

I already have the scheduling and communication aspect of the job in place.

I want to return all the lines which match the criteria , and then only the part of the line which is relevant.

For example:

12 May 2017 the file myBACKUPfile.BAK was transferred to the target destination

I want to return the text file myBACKUPfile.BAK

How can I use powershell to get this result?


Answer: Powershell has a cmdlet called select-string. Combining select-string with regex is a good basis to start. There are alternative ways of getting the same results.But in terms of simplicity and functionality – this method is effective

Here is an example of a line of Powershell code.

get-content "N:\mypath\myfile.txt"|select-string "^(?!.*(file)).*[a-zA-Z0-9].BAK"


This code grabs the content with the get-content cmdlet. We are asking for some action to occur on this content. The select-string cmdlet is used to search for a text pattern between two words.

In this case I’m using regular expressions to apply the pattern, The two words are “file” and “.BAK” .

In summary , the code is consuming a file , and then searching for a text pattern between two words and returns a list.

You may then want to push to another file and  Send email from Powershell with attachment  or place into a database etc



Author: Jack Vamvas (http://www.sqlserver-dba.com)


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