Often you may want to use PowerShell to find all lines in a particular file that do not match a specific pattern.
You can use the following basic syntax with the -notmatch operator to do so:
Get-Content employees.txt | Where {$_ -notmatch 'A\d\d\d'}
This particular example will return all lines from the text file named employees.txt that do not contain a string with the letter ‘A’ followed by three numeric characters.
Note that we used the Regex pattern \d to match numbers between 0 and 9.
Note that you can use any Regex pattern you would like in the quotes following the -notmatch operator to search for specific patterns.
The following example shows how to use this syntax in practice.
Example: How to Use Regex with -notmatch in PowerShell
Suppose we have a file named employees.txt that contains the ID numbers for various employees at some company.
We can use the Get-Content cmdlet to view the contents of this file:
Suppose that we would like to return all lines in the file that do not contain a pattern that matches the letter ‘A’ followed by three numeric characters.
We can use the following syntax to do so:
Get-Content employees.txt | Where {$_ -notmatch 'A\d\d\d'}
The following screenshot shows how to use this syntax in practice:
Notice that this returns all lines in the file that do not contain the pattern that we specified.
Feel free to use any Regex pattern that you’d like following the -notmatch operator to search for any specific pattern.
Note: You can find the complete documentation for the -notmatch operator in PowerShell here.
Related Tutorials
The following tutorials explain how to perform other common tasks in PowerShell:
PowerShell: How to Use Regex in Switch Statement
PowerShell: How to Use Regex to Capture All Matches
PowerShell: How to Split String Based on Regex Pattern
