Some time ago I received the question what the operators ‘-eq’, ’-lt’ and ‘-ne’ mean, what other operators they are and whatever else I could tell about them. I think this is a good topic for a blog post since most beginning PowerShell scripters don’t know which operators are available to them… and for your convenience I’ve provided some real-life examples 
There are two kinds: Comparison and logical operators.
Comparison Operators
These operators are used to compare values to conditions you specify. There are a bunch of operators in this category, so let’s name and explain them one at a time:
| Operator |
-eq |
| Name: |
Equal to. |
| Description: |
Used to compare an identical value. |
| Example: |
Get-childitem | where {$_.Name –eq “PowerShell notes”} |
| Explanation: |
Will find all files where the name of the file is equal to “PowerShell notes”. |
| Operator |
-ne |
| Name: |
Not equal to. |
| Description: |
Used to compare a different value. |
| Example: |
Get-childitem | where {$_.Name –ne “PowerShell notes”} |
| Explanation: |
Will find all files where the name is not equal to “PowerShell notes”. |
| Operator |
-gt |
| Name: |
Greater than |
| Description: |
Used to compare a different value in size. |
| Example: |
Get-childitem | where {$_.Length –gt 1MB} |
| Explanation: |
Will find all files where the size is greater than 1MB. |
| Operator |
-ge |
| Name: |
Greater than or equal to |
| Description: |
Used to compare a different or identical value in size. |
| Example: |
Get-childitem | where {$_.Length –ge 1MB} |
| Explanation: |
Will find all files where the size is equal to or greater than 1MB. |
| Operator |
-lt |
| Name: |
Less than |
| Description: |
Used to compare a different value in size. |
| Example: |
Get-childitem | where {$_.Length –lt 1MB} |
| Explanation: |
Will find all files where the size is less than 1MB. |
| Operator |
-le |
| Name: |
Less than or equal to |
| Description: |
Used to compare a different or identical value in size. |
| Example: |
Get-childitem | where {$_.Length –le 1MB} |
| Explanation: |
Will find all files where the size is equal to or less than 1MB. |
| Operator |
-like |
| Name: |
Like |
| Description: |
Match an identical value using a wildcard character. |
| Example: |
Get-childitem | where {$_.Name –like “PowerShell*”} |
| Explanation: |
Will find all files where the name begins with “PowerShell”. |
| Operator |
-notlike |
| Name: |
Not like |
| Description: |
Does not match an identical value using a wildcard character. |
| Example: |
Get-childitem | where {$_.Name –notlike “PowerShell*”} |
| Explanation: |
Will find all files where the name does not begin with “PowerShell”. |
| Operator |
-match |
| Name: |
Match |
| Description: |
Used to compare a string using a regular expression. |
| Example: |
Get-childitem | where {$_.Name –match “Power”} |
| Explanation: |
Will find all files where the name contains “Power”. |
| Operator |
-notmatch |
| Name: |
Not match |
| Description: |
Used to compare a string using a regular expression. |
| Example: |
Get-childitem | where {$_.Name –notmatch “Power”} |
| Explanation: |
Will find all files where the name does not contain “Power”. |
| Operator |
-contains |
| Name: |
Contains |
| Description: |
Used to see if all of the objects that are provided contain a specific value. |
| Example: |
“Microsoft”, “Windows”, “PowerShell” –contains “Power” |
| Explanation: |
Looks if the string “Power” is included in all of the provided objects and therefor it will answer “False” to that question. |
| Operator |
-notcontains |
| Name: |
Not contains |
| Description: |
Used to see if all of the objects that are provided do not contain a specific value. |
| Example: |
“Windows”, “PowerShell” -notcontains “Power” |
| Explanation: |
Looks if the string “Power” is not included in all of the provided objects and therefor it will answer “True” to that question. |
| Operator |
-replace |
| Name: |
Replace |
| Description: |
Used to change the value of an element. |
| Example: |
Get-childitem –include *.doc | where {$_ –replace “.doc”, “.docx”} |
| Explanation: |
Will find all *.doc files and changes their extension from .doc to .docx |
| Note: |
This command only changed the extension, it does not convert the file to a new format! |
Logical Operators
These operators are used to connect multiple expressions and/or statements to each other. This will allow you to use a one expression and test them against multiple conditions:
| Operator |
-and |
| Name: |
And |
| Description: |
Logical “and”. Only true when both statements are true. |
| Example: |
Get-childitem | where {($_.Length -gt 1MB ) -and ($_.Length -lt 10MB ) } |
| Explanation: |
Will find all files where the size is between 1MB and 10 MB. |
| Operator |
-or |
| Name: |
Or |
| Description: |
Logical “or”. Only true when either or both statements are true. |
| Example: |
Get-childitem | where {($_.Name –like “*Microsoft*” ) –or ($_.Name –like “*Citrix*” ) } |
| Explanation: |
Will find all files where the name includes either “Microsoft” or “Citrix”. |
| Operator |
-xor |
| Name: |
Exclusive or |
| Description: |
Logical “exclusive or”. Only true when one of the statements is true and the other is false. |
| Example: |
Get-childitem | where {($_.Name –like “*Microsoft*” ) –xor ($_.Name –like “*RDS*” ) } |
| Explanation: |
Will find all files where the name includes “Microsoft” but does not include “RDS”. |
| Operator |
-not |
| Name: |
Not |
| Description: |
Logical “not”. Negates the statement that follows. |
| Example: |
Get-childitem | where {($_.Name –like “*Microsoft*” ) –and –not ($_.Length –gt 1MB ) } |
| Explanation: |
Will find all files where the name includes “Microsoft” and the file is not greater than 1MB. |
| Operator |
! |
| Name: |
Not |
| Description: |
The same as operator –not |
| Example: |
Get-childitem | where {($_.Name –like “*Microsoft*” ) –and !($_.Length –gt 1MB ) } |
| Explanation: |
The same as operator –not |
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