Something to -notlike about the -like operator in PowerShell

I recently ran into a problem with the PowerShell like operator that I wanted to share since what’s occurring may not be immediately apparent.

The like operator allows for comparison tests of strings using wildcard characters instead of exact matches. I think of it being similar to the match operator except like uses simple wildcards instead of regular expressions.


Easy enough, right? A string on the left and another string with wildcards on the right. If it matches, true is returned otherwise if it doesn’t match, false is returned.

The dilemma is when you decide to use wildcard characters on the left side instead of on the right:


Conventional wisdom would make you think that either of these examples would return true but as you can see in the previous set of results, don’t make assumptions otherwise you could spend countless hours troubleshooting a larger script or function where something like the second example is used and it could cost you a lot of time as well as your sanity.

The characters listed in the about_Wildcards help topic have special meaning when used on the right side of the like operator. If they’re used on the left side of the like operator, they’re literals and have no special meaning.

Their special meaning can be escaped on the right side of the like operator using the backtick character as mentioned in the about_Quoting_Rules help topic.


See the about_Comparision_Operators help topic to learn more about the PowerShell like operator. Also consider taking a look at the previously referenced about_Wildcards help topic to learn more about advanced wildcards that can be used with the like operator such as a range of characters.


1 Comment

  1. jtbailey

    In almost all shells flow is almost always left to right, only in certain circumstances would it be right to left. Conventional Wisdom from a mathematics point of view, you are correct, however, you’re not working in an environment that handles just mathematics.


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