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about_Comparison_Operators

Updated: December 3, 2014

Applies To: Windows PowerShell 2.0, Windows PowerShell 3.0, Windows PowerShell 4.0

TOPIC
    about_Comparison_Operators

SHORT DESCRIPTION
    Describes the operators that compare values in Windows PowerShell.

LONG DESCRIPTION
    Comparison operators let you specify conditions for comparing values and
    finding values that match specified patterns. To use a comparison operator,
    specify the values that you want to compare together with an operator that
    separates these values.

    Windows PowerShell includes the following comparison operators:

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

    By default, all comparison operators are case-insensitive. To make a 
    comparison operator case-sensitive, precede the operator name with a "c".
    For example, the case-sensitive version of "-eq" is "-ceq". To make the
    case-insensitivity explicit, precede the operator with an "i". For example,
    the explicitly case-insensitive version of "-eq" is "-ieq".

    When the input to an operator is a scalar value, comparison operators
    return a Boolean value. When the input is a collection of values, the 
    comparison operators return any matching values. If there are no matches
    in a collection, comparison operators do not return anything. 

    The exceptions are the containment operators (-Contains, -NotContains),
    the In operators (-In, -NotIn), and the type operators (-Is, -IsNot),
    which always return a Boolean value.

    Windows PowerShell supports the following comparison operators.

    -eq
      Description: Equal to. Includes an identical value.
      Example:

        PS C:\> "abc" -eq "abc"
        True

        PS C:\> "abc" -eq "abc", "def"
        False

        PS C:\> "abc", "def" -eq "abc"
        abc


    -ne
      Description: Not equal to. Includes a different value.
      Example:

        PS C:\> "abc" -ne "def"
        True

        PS C:\> "abc" -ne "abc"
        False

        PS C:\> "abc" -ne "abc", "def"
        True

        PS C:\> "abc", "def" -ne "abc"
        def



    -gt
      Description: Greater-than.
      Example:

          PS C:\> 8 -gt 6
          True

          PS C:\> 7, 8, 9 -gt 8
          9


    -ge
      Description: Greater-than or equal to.
      Example:

          PS C:\> 8 -ge 8
          True         

          PS C:\> 7, 8, 9 -ge 8
          8
          9


    -lt
      Description: Less-than.
      Example:

          PS C:\> 8 -lt 6
          False

          PS C:\> 7, 8, 9 -lt 8
          7

    -le
      Description: Less-than or equal to.
      Example:

          PS C:\> 6 -le 8
          True

          PS C:\> 7, 8, 9 -le 8
          7
          8

    -Like
      Description: Match using the wildcard character (*).
      Example:

          PS C:\> "Windows PowerShell" -like "*shell"
          True

          PS C:\> "Windows PowerShell", "Server" -like "*shell"
          Windows PowerShell


    -NotLike
      Description: Does not match using the wildcard character (*).
      Example:

          PS C:\> "Windows PowerShell" -NotLike "*shell"
          False

          PS C:\> "Windows PowerShell", "Server" -NotLike "*shell"
          Server               


    -Match 
      Description: Matches a string using regular expressions. 
                   When the input is scalar, it populates the
                   $Matches automatic variable. 
      Example:

                                      
          PS C:\> "Sunday" -Match "sun" 
          True 

          PS C:\> $matches 
          Name Value 
          ---- ----- 
          0    Sun
 
          PS C:\> "Sunday", "Monday" -Match "sun" 
          Sunday
 

    -NotMatch
      Description: Does not match a string. Uses regular expressions.
                   When the input is scalar, it populates the $Matches
                   automatic variable. 
      Example:

          PS C:\> "Sunday" -NotMatch "sun"
          False

          PS C:\> $matches 
          Name Value 
          ---- ----- 
          0    sun

          PS C:\> "Sunday", "Monday" -NotMatch "sun" 
          Monday


    -Contains
      Description: Containment operator. Tells whether a collection of reference
      values includes a single test value. Always returns a Boolean value. Returns TRUE
      only when the test value exactly matches at least one of the reference values. 

      When the test value is a collection, the Contains operator uses reference
      equality. It returns TRUE only when one of the reference values is the same
      instance of the test value object.

      Syntax: 
          <Reference-values> -Contains <Test-value>

      Examples:

          PS C:\> "abc", "def" -Contains "def"
          True

          PS C:\> "Windows", "PowerShell" -Contains "Shell"
          False  #Not an exact match


          # Does the list of computers in $domainServers
          # include $thisComputer?
          # -------------------------------------------
          PS C:\> $domainServers -Contains $thisComputer
          True

          PS C:\> "abc", "def", "ghi" -Contains "abc", "def"
          False

          PS C:\> $a = "abc", "def"
          PS C:\> "abc", "def", "ghi" -Contains $a
          False
          PS C:\> $a, "ghi" -Contains $a
          True


    -NotContains
      Description: Containment operator. Tells whether a collection of reference
      values includes a single test value. Always returns a Boolean value. Returns
      TRUE when the test value is not an exact matches for at least one of the reference
      values. 

      When the test value is a collection, the NotContains operator uses reference
      equality. 

      Syntax: 
          <Reference-values> -NotContains <Test-value>

      Examples:

          PS C:\> "Windows", "PowerShell" -NotContains "Shell"
          True  #Not an exact match


          # Get cmdlet parameters, but exclude common parameters
          function get-parms ($cmdlet)
          {
              $Common = "Verbose", "Debug", "WarningAction", "WarningVariable", `
                        "ErrorAction", "ErrorVariable", "OutVariable", "OutBuffer" 
    
              $allparms = (Get-Command $Cmdlet).parametersets | foreach {$_.Parameters} | `
                          foreach {$_.Name} | Sort-Object | Get-Unique
    
              $allparms | where {$Common -NotContains $_ }
          }


          # Find unapproved verbs in the functions in my module
          # -------------------------------------------
          PS C:\> $ApprovedVerbs = Get-Verb | foreach {$_.verb}
          PS C:\> $myVerbs = Get-Command -Module MyModule | foreach {$_.verb}

          PS C:\> $myVerbs | where {$ApprovedVerbs -NotContains $_}      
          ForEach
          Sort
          Tee
          Where


    -In
      Description: In operator. Tells whether a test value appears in a collection
      of reference values. Always return as Boolean value. Returns TRUE only when
      the test value exactly matches at least one of the reference values. 

      When the test value is a collection, the In operator uses reference equality. 
      It returns TRUE only when one of the reference values is the same
      instance of the test value object.
   
      The In operator was introduced in Windows PowerShell 3.0.

      Syntax: 
         <Test-value> -in <Reference-values> 

      
      Examples:

          PS C:\> "def" -in "abc", "def"
          True

          PS C:\> "Shell" -in "Windows", "PowerShell"
          False  #Not an exact match

          PS C:\> "Windows" -in "Windows", "PowerShell"
          True  #An exact match

          PS C:\> "Windows", "PowerShell" -in "Windows", "PowerShell", "ServerManager"
          False  #Using reference equality

          PS C:\> $a = "Windows", "PowerShell"
          PS C:\> $a -in $a, "ServerManager"
          True  #Using reference equality

          # Does the list of computers in $domainServers
          # include $thisComputer?
          # -------------------------------------------
          PS C:\> $thisComputer -in  $domainServers
          True
     

    -NotIn
      Description: NotIn operator. Tells whether a test value appears in a collection
      of reference values. Always returns a Boolean value. Returns TRUE when the test
      value is not an exact match for at least one of the reference values. 

      When the test value is a collection, the In operator uses reference equality. 
      It returns TRUE only when one of the reference values is the same
      instance of the test value object.

      The NotIn operator was introduced in Windows PowerShell 3.0.

      Syntax: 
         <Test-value> -NotIn <Reference-values> 

      
      Examples:

          PS C:\> "def" -NotIn "abc", "def"
          False

          PS C:\> "ghi" -NotIn "abc", "def"
          True

          PS C:\> "Shell" -NotIn "Windows", "PowerShell"
          True  #Not an exact match

          PS C:\> "Windows" -NotIn "Windows", "PowerShell"
          False  #An exact match



          # Find unapproved verbs in the functions in my module
          # -------------------------------------------
          PS C:\> $ApprovedVerbs = Get-Verb | foreach {$_.verb}
          PS C:\> $myVerbs = Get-Command -Module MyModule | foreach {$_.verb}

          PS C:\> $myVerbs | where {$_ -NotIn $ApprovedVerbs}      
          ForEach
          Sort
          Tee
          Where



    -Replace
      Description: Replace operator. Changes the specified elements of a value.
      Example:


          PS C:\> "Get-Process" -Replace "Get", "Stop"
          Stop-Process

          # Change all .GIF file name extension to .JPG
          PS C:\> dir *.gif | foreach {$_ -Replace ".gif", ".jpg"} 
               




  Equality Operators
      The equality operators (-eq, -ne) return a value of TRUE or the matches
      when one or more of the input values is identical to the specified 
      pattern. The entire pattern must match an entire value.

          C:PS> 2 -eq 2
          True

          C:PS> 2 -eq 3
          False

          C:PS> 1,2,3 -eq 2
          2

          C:PS> "PowerShell" -eq "Shell"
          False

          C:PS> "Windows", "PowerShell" -eq "Shell"
          C:PS> 

          PS C:\> "abc", "def", "123" -eq "def"
          def
 
          PS C:\> "abc", "def", "123" -ne "def"
          abc
          123


  Containment Operators
      The containment operators (-Contains and -NotContains) are similar to the
      equality operators. However, the containment operators always return a 
      Boolean value, even when the input is a collection. 

      Also, unlike the equality operators, the containment operators return a 
      value as soon as they detect the first match. The equality operators 
      evaluate all input and then return all the matches in the collection.
      The following examples show the effect of the -Contains operator:

          C:PS> 1,2,3 -contains 2
          True

          C:PS> "PowerShell" -contains "Shell"
          False

          C:PS> "Windows", "PowerShell" -contains "Shell"
          False

          PS C:\> "abc", "def", "123" -contains "def"
          True

          PS C:\> "true", "blue", "six" -contains "true"
          True
 

      The following example shows how the containment operators differ from the
      equal to operator. The containment operators return a value of TRUE on the 
      first match.
 

          PS C:\> 1,2,3,4,5,4,3,2,1 -eq 2
          2
          2

          PS C:\> 1,2,3,4,5,4,3,2,1 -contains 2
          True
 
      
      In a very large collection, the -Contains operator returns results 
      quicker than the equal to operator.


  Match Operators
      The match operators (-Match and -NotMatch) find elements that match or
      do not match a specified pattern using regular expressions. 

      The syntax is:

          <string[]> -Match <regular-expression>
          <string[]> -NotMatch <regular-expression>


      The following examples show some uses of the -Match operator:


          PS C:\> "Windows", "PowerShell" -Match ".shell"
          PowerShell

          PS C:\> (Get-Command Get-Member -Syntax) -Match "-view"
          True

          PS C:\> (Get-Command Get-Member -Syntax) -NotMatch "-path"
          True

          PS C:\> (Get-Content Servers.txt) -Match "^Server\d\d"
          Server01
          Server02

         
      The match operators search only in strings. They cannot search in arrays
      of integers or other objects. 

      The -Match and -NotMatch operators populate the $Matches automatic
      variable when the input (the left-side argument) to the operator
      is a single scalar object. When the input is scalar, the -Match and
      -NotMatch operators return a Boolean value and set the value of the
      $Matches automatic variable to the matched components of the argument.

      If the input is a collection, the -Match and -NotMatch operators return
      the matching members of that collection, but the operator does not
      populate the $Matches variable.

      For example, the following command submits a collection of strings to
      the -Match operator. The -Match operator returns the items in the collection
      that match. It does not populate the $Matches automatic variable.

          PS C:\> "Sunday", "Monday", "Tuesday" -Match "sun"
          Sunday

          PS C:\> $matches
          PS C:\>


      In contrast, the following command submits a single string to the
      -Match operator. The -Match operator returns a Boolean value and 
      populates the $Matches automatic variable.

          PS C:\> "Sunday" -Match "sun"
          True

          PS C:\> $matches

          Name                           Value
          ----                           -----
          0                              Sun


      The -NotMatch operator populates the $Matches automatic variable when
      the input is scalar and the result is False, that it, when it detects
      a match.


          PS C:\> "Sunday" -NotMatch "rain"
          True

          PS C:\> $matches
          PS C:\>
          
          PS C:\> "Sunday" -NotMatch "day"
          False

          PS C:\> $matches
          PS C:\>

          Name                           Value
          ----                           -----
          0                              day

        
  Replace Operator
      The -Replace operator replaces all or part of a value with the specified 
      value using regular expressions. You can use the -Replace operator for 
      many administrative tasks, such as renaming files. For example, the 
      following command changes the file name extensions of all .gif files
      to .jpg:
 

          Get-ChildItem | Rename-Item -NewName { $_ -Replace '.gif$','.jpg$' }

 
      The syntax of the -Replace operator is as follows, where the <original> 
      placeholder represents the characters to be replaced, and the
      <substitute> placeholder represents the characters that will replace 
      them:


          <input> <operator> <original>, <substitute> 


      By default, the -Replace operator is case-insensitive. To make it case 
      sensitive, use -cReplace. To make it explicitly case-insensitive, use 
      -iReplace. Consider the following examples:


          PS C:\> "book" -Replace "B", "C"
          Cook
          PS C:\> "book" -iReplace "B", "C" 
          Cook
          PS C:\> "book" -cReplace "B", "C"
          book
 
         PS C:\> '<command:parameter required="false" variableLength="true" globbing="false"'`
                 | foreach {$_ -replace 'globbing="false"', 'globbing="true"'}
         <command:parameter required="false" variableLength="true" globbing="true"



  Bitwise Operators
      Windows PowerShell supports the standard bitwise operators, including
      bitwise-AND (-bAnd), the inclusive and exclusive bitwise-OR operators 
      (-bOr and -bXor), and bitwise-NOT (-bNot). 

      Beginning in Windows PowerShell 2.0, all bitwise operators work with 
      64-bit integers.

      Beginning in Windows PowerShell 3.0, the -shr (shift-right) and 
      -shl (shift-left) are introduced to support bitwise arithmetic in 
      Windows PowerShell.


      Windows PowerShell supports the following bitwise operators.

      Operator  Description               Example  
      --------  ----------------------    -------------------
      -bAnd     Bitwise AND               PS C:\> 10 -band 3
                                          2
 
      -bOr      Bitwise OR (inclusive)    PS C:\> 10 -bor 3
                                          11    

      -bXor     Bitwise OR (exclusive)    PS C:\> 10 -bxor 3
                                          9

      -bNot     Bitwise NOT               PS C:\> -bNot 10
                                          -11

      -shl      Shift-left                PS C:\> 100 -shl 2
                                          400
 
      -shr      Shift-right               PS C:\> 100 -shr 1
                                          50
 


      Bitwise operators act on the binary format of a value. For example, the
      bit structure for the number 10 is 00001010 (based on 1 byte), and the
      bit structure for the number 3 is 00000011. When you use a bitwise 
      operator to compare 10 to 3, the individual bits in each byte are
      compared.
 

      In a bitwise AND operation, the resulting bit is set to 1 only when both 
      input bits are 1.


          1010      (10)
          0011      ( 3)
          --------------  bAND
          0010      ( 2)

 
      In a bitwise OR (inclusive) operation, the resulting bit is set to 1 
      when either or both input bits are 1. The resulting bit is set to 0 only
      when both input bits are set to 0.


          1010      (10)
          0011      ( 3)
          --------------  bOR (inclusive)
          1011      (11)


      In a bitwise OR (exclusive) operation, the resulting bit is set to 1 only
      when one input bit is 1.


          1010      (10)
          0011      ( 3)
          --------------  bXOR (exclusive)
          1001      ( 9)
 

      The bitwise NOT operator is a unary operator that produces the binary
      complement of the value. A bit of 1 is set to 0 and a bit of 0 is set
      to 1. 

      For example, the binary complement of 0 is -1, the maximum unsigned 
      integer (0xffffffff), and the binary complement of -1 is 0.


          PS C:\> -bNOT 10
          -11


          0000 0000 0000 1010  (10)
          ------------------------- bNOT
          1111 1111 1111 0101  (-11, xfffffff5) 



      In a bitwise shift-left operation, all bits are moved "n" places to 
      the left, where "n" is the value of the right operand. A zero is 
      inserted in the ones place. 

      When the left operand is an Integer (32-bit) value, the lower 5 bits
      of the right operand determine how many bits of the left operand are 
      shifted.

      When the left operand is a Long (64-bit) value, the lower 6 bits of 
      the right operand determine how many bits of the left operand are 
      shifted.

        PS C:\> 21 -shl 1
        42

          00010101  (21)
          00101010  (42)

        PS C:\> 21 -shl 2
        84

          00010101  (21)
          00101010  (42)
          01010100  (84)


      In a bitwise shift-right operation, all bits are moved "n" places
      to the right, where "n" is specified by the right operand. The 
      shift-right operator (-shr) inserts a zero in the left-most 
      place when shifting a positive or unsigned value to the right.

      When the left operand is an Integer (32-bit) value, the lower 5 bits
      of the right operand determine how many bits of the left operand are 
      shifted.

      When the left operand is a Long (64-bit) value, the lower 6 bits of 
      the right operand determine how many bits of the left operand are 
      shifted.

        PS C:\> 21 -shr 1
        10

          00010101  (21)
          00001010  (10)

        PS C:\> 21 -shr 2
        5

          00010101  (21)
          00001010  (10)
          00000101  ( 5)



SEE ALSO
    about_Operators
    about_Regular_Expressions
    about_Wildcards
    Compare-Object
    Foreach-Object
    Where-Object



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