about_Comparison_Operators | Easy Powershell 2.0 Reference

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.

    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”.

    All comparison operators except the containment operators
    (-contains, -notcontains) and type operators (-is, -isnot) return a Boolean
    value when the input to the operator (the value on the left side of the
    operator) is a single value (a scalar). When the input is a collection of
    values, the containment operators and the type operators return any
    matching values. If there are no matches in a collection, these operators
    do not return anything. The containment operators and type operators always
    return a Boolean value.

Windows PowerShell supports the following comparison operators.

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

C:\PS> “abc”, “def” -eq “abc”
abc

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

C:\PS> “abc”, “def” -ne “abc”
def

    -gt
     Description: Greater-than.
     Example:

C:\PS> 8 -gt 6
True

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

C:\PS> 8 -ge 8
True

    -lt
     Description: Less-than.
     Example:

C:\PS> 8 -lt 6
False

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

C:\PS> 6 -le 8
True

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

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

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

C:\PS> “Windows PowerShell” -notlike “*shell”
False

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

C:\PS> “Sunday” -match “sun”
True

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

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

C:\PS> “Sunday” -notmatch “sun”
False

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

    -contains
     Description: Containment operator. Includes an identical value that is
     not part of a value. Always returns a Boolean value.
     Example:

C:PS> “abc”, “def” -contains “def”
True

    -notcontains
     Description: Containment operator. Does not include an identical value.
     Always returns Boolean.
     Example:

C:PS> “Windows”, “PowerShell” -notcontains “Shell”
True

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

C:\PS> “Get-Process” -replace “Get”, “Stop”
Stop-Process

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.

The following examples show the effect of the equal to operator:

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

C:PS> “PowerShell” -eq “Shell”
False

C:PS> “Windows”, “PowerShell” -eq “Shell”
C:PS>

C:\PS> “abc”, “def”, “123” -eq “def”
def

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

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

C:\PS> “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.

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

C:\PS> 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:

C:\PS> “Windows”, “PowerShell” -match “.shell”
PowerShell

C:\PS> (Get-Command Get-Member -syntax) -match “-view”
True

C:\PS> (Get-Command Get-Member -syntax) -notmatch “-path”
True

         C:\PS> (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.

C:\PS> “Sunday”, “Monday”, “Tuesday” -match “sun”
Sunday

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

     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.

C:\PS> “Sunday” -match “sun”
True

C:\PS> $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.

C:\PS> “Sunday” -notmatch “rain”
True

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

C:\PS> “Sunday” -notmatch “day”
False

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

         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:

     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:

         C:\PS> “book” -replace “B”, “C”
         Cook
         C:\PS> “book” -ireplace “B”, “C”
         Cook
         C:\PS> “book” -creplace “B”, “C”
         book

Bitwise Operators
     Windows PowerShell supports the standard bitwise operators, including
     bitwise-AND (-band), and inclusive and exclusive bitwise-OR operators
     (-bor and -bxor). Beginning in Windows PowerShell 2.0, all bitwise
     operators work with 64-bit integers.

Windows PowerShell supports the following bitwise operators.

     Operator Description             Example
     ——– ———————-    ——————-
     -band     Bitwise AND             C:\PS> 10 -band 3
                                         2

-bor Bitwise OR (inclusive) C:\PS> 10 -bor 3
11

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

     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.

         00001010     (10)
         00000011     ( 3)
         —————— bAND
         00000010     ( 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.

         00001010     (10)
         00000011     ( 3)
         —————— bOR (inclusive)
         00001011     (11)

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

         00001010     (10)
         00000011     ( 3)
         —————— bXOR (exclusive)
         00001001     ( 9)

SEE ALSO
    about_operators
    about_regular_expressions
    about_wildcards
    Compare-Object