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