New PowerShell 3.0 Comparators -NotIn and -In
PowerShell 1.0 not only has comparison operators such as -Match, -Like and -Contains, but also their negative counterparts such as -NotContains.
Here in PowerShell 3 we have two new members of the comparsion operators team: -In and -NotIn.
Windows PowerShell -In Topics
- Example 1: Testing Numbers in a Range
- Example 2: PowerShell’s -NotIn
- The Secret to Understanding PowerShell 3’s -In and -NotIn
- Comparing PowerShell’s -In with -Match
- Troubleshooting PowerShell -In and -NotIn
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Example 1: Testing Numbers in a Range
In this example we are asking PowerShell the question: ‘Is 77 in the range 70 to 80?’
# PowerShell -In
77 -In 70..80
True
Note 1: The key to using -In (and -NotIn) is mastering the ranging dots .. between the values
Example 2: PowerShell’s -NotIn
Once you have mastered the -In comparator, you’ll have no trouble with its sister command -NotIn, it works in a complimentary manner in according to what logic would predict.
# PowerShell -NotIn
5 -NotIn 70..80
True
The Secret to Understanding PowerShell 3’s -In and -NotIn
The easiest way to learn which comparator to choose for which script is to compare them! That is how I appreciated the nuances of -Like and -Match. In the case of -In, substitute -Contains and observe the similarities and differences. For me, it all comes down to those two ranging dots, which -In loves, but -Contains seems to ignore.
# Windows PowerShell -Contains
77 -Contains 70..80
False
Note 2: This makes no sense, thus abandon -Contains and go back to -In. See Example 2 above
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Comparing Windows PowerShell’s -In with -Match
# PowerShell -Match
‘8080’ -Match ’80’
True
But ’80’ -Match ‘8080’ would be False
# PowerShell -In
‘8080’ -In ’80’
False
Also ’80’ -In ‘8080’ would be False
Conclusion: PowerShell’s -In works best with a range expressed as: 0..8080. In my opinion -In (or -NotIn) are rarely the best comparison operator for text.
# PowerShell -In
’80’ -In ‘1..8080’
True
Troubleshooting PowerShell -In and -NotIn
Incorrect version of PowerShell
You must provide a value expression on the right-hand side of the ‘-‘ operator.
At line:2 char:6
Unexpected token ‘in’ in expression or statement.
This is what you get in PowerShell 1.0 or 2.0, -In is new in PowerShell 3.0
Dottiness
You get the ‘wrong’ result, 'False' when all logic tells you it should be true. Check you have two ranging dots .. and not three … dots. Strange but true!
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Further Research on Conditional Operators
-In and -NotIn are members of PowerShell's conditional operators. A good way to research these operators is with:
Help about_Comparison_Operators
See more of what’s new in PowerShell v 3.0 »
Summary of PowerShell -In and -NotIn
PowerShell 1.0 uses comparison operators such as, -Match, -Like and -Contains, PowerShell 3.0 brings -In and -NotIn. The key to understanding these latest operators is to pay close attention to the ranging .. dots.
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See more Microsoft PowerShell v 3.0
• PowerShell 3.0 • What’s New in PowerShell 3.0 • PowerShell 3.0 Foreach-Object
• PowerShell Show-Command • Out-GridView -PassThru • PowerShell Ordered Hash Tables
• PowerShell Home • PowerShell 3.0 Get-ChildItem • PowerShell 3 -NotIn • PowerShell 3.0 Where
