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
- PowerShell’s -eq in a ‘Where clause’
- Example of PowerShell’s -eq and -ne Operators
- PowerShell’s Greater Than Comparison Operator -gt
- -Match, -Like, and -Contains
- PowerShell If and ElseIf
- PowerShell 3’s -In and -NotIn
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 -autoLearning 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
- Compare-Object
- Compare-Object Registry
- Conditional Operators: -Like -Match – contains
- If Statement (also ElseIf)
- -Match and -NotMatch
- Quotes ‘Single’ or “Double”?
- Syntax
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.
