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About Comparison Operators

JuanPablo Jofre|Last Updated: 11/17/2016
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2 Contributors

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: -Contains

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: -NotContains

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: -in

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: -NotIn

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:

<_string5b_5d_> -Match <_string5b_5d_> -NotMatch

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 placeholder represents the characters to be replaced, and the 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:

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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