PowerShell's Comparison Operators

Windows PowerShell's Comparison Operators

For PowerShell newbies one of the strangest comparison operators is -eq.  While you still need the equals sign '=' for declaring variables, in most other cases you need PowerShell's -eq.

At first using -ne for 'not equal' also seems odd, but once you warm to this theme of dash followed by initial letters, then -gt (greater than) or -lt (less than) will seem a logical continuation.  Consequently, abandon > <, instead employ -gt or -lt instead.

Examples of Comparison Operators in PowerShell

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A Classic Example of PowerShell's -eq in a 'Where clause'

# PowerShell script to list DLLs under system32 folder
$Dir = Get-Childitem C:\windows\system32 -recurse -EA SilentlyContinue
$List = $Dir | Where-Object {$_.extension -eq ".dll"}
$List | Format-Table Name, CreationTime -auto

Learning Points

Note 1:  About the only tricky aspect of the -eq syntax is whether to put the comparison object in single or double quotes.  The difference is that "Double Quotes" expands any variables; whereas 'single quotes' are treated as literals.  In this example either ".dll" or '.dll' would achieve the desired listing.   See more about quotes here.

Example of PowerShell's -eq and -ne Operators

The point of the following real-life script is to test for internet connectivity.  If there is none, then PowerShell can cure this particular browser problem by restarting the dnscache service.

# PowerShell Script to Test An Internet Connection
$DNS = (Test-Connection www.google.com -quiet)
If($DNS -eq "True") {Write-Host "The internet is available"}
ElseIf($DNS -ne "True") {Restart-Service dnscache}

Learning Points

Note 2: We employ an 'If' statement to act upon the output of the Test-Connection cmdlet.

Note 3: Remember that instead of an equal sign (=), PowerShell uses -eq.  One benefit is that it's easy to use the negative -ne (PowerShell's not equal).

-Eq Operator with .txt File Extensions

# PowerShell Comparison Operator -eq in Foreach Loop
"File Name " + "`t Size" +"`t Last Accessed"
foreach ($file in Get-Childitem)
{If ($file.extension -eq ".txt")
    {
     $file.name + "`t " +$file.length + "`t " +    $file.LastAccessTime
    }
}

Note 4: For the sake of completeness, there is also -Ceq where 'c' means case-sensitive.

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Example of PowerShell's Greater Than Comparison Operator -gt

In PowerShell, greater than is abbreviated to -gt.  Observe how both -gt and -lt (less than) are preceded by a dash.

Clear-Host
$FileSource ="D:\"
$Block = Get-ChildItem -path $Filesource -Recurse
$Block | Where-Object {$_.length -gt 2MB}

Learning Points

Note 5:  The point of the above comparison example is to find large files; to be precise to list files greater than 2MB.

Note 6:  As 2MB is a pure number it needs no quotes.

Note 7:  Be aware that if you want to get this example to work you either need a D: drive, or else change the value of $FileSource.

PowerShell's Less Than Comparison Operator -lt

Just as -eq has an opposite in -ne, so -gt (greater than) has a mirror image in -lt (less than).  In other scripting languages these would be represented by > and < symbols, however PowerShell uses the dash then an abbreviation of the comparison operator, thus -lt.

Speaking of > and <, they have >= and <= to represent greater than or equal and less than or equal.  In PowerShell such concepts involving equal are represented by -ge and -le, where 'e' stands for equal.

Here is an example not of -lt, but -le meaning less than or equal.  What it does is calculate and display the 12 times table.

For ( $i = 12; $i -le 144; $i+=12 ) { $i }

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Similar PowerShell Operators

Research with: About_Comparison_Operators

# For even more information about PowerShell Operators try:
Get-Help about_Comparison_Operators

Here is the Complete List of PowerShell's Comparison Operators

-eq
-ne
-gt
-ge
-lt
-le
-Like
-NotLike
-Match
-NotMatch
-Contains
-NotContains
-In
-NotIn
-Replace

Normally all these comparison operators are not case sensitive. However, to select on the precise UPPER or Proper case precede the operator name with a "c".
For example, "-cmatch"

See a review of PowerShell math »

Summary of PowerShell's Comparison Operators

PowerShell uses the equals sign '=' for declaring variables, but for genuine comparison operations you need -eq.  Also, for not equal, use the -ne operator.  When comparing greater than or less than, it is logical to use -gt and -lt, avoid > or < in these instances.

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See more Windows PowerShell flow control examples

PowerShell Switch Statement  • PowerShell Real-life Techniques  • Free Permissions Analyzer

Differences between For, ForEach and ForEach-Object  • PowerShell Loops  • PowerShell Home

Conditional Operators   • Do While Loop  • PowerShell If Statement  • PowerShell Brackets

Please email me if you have a better example script. Also please report any factual mistakes, grammatical errors or broken links, I will be happy to correct the fault.

 

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