Export (0) Print
Expand All
Expand Minimize
This topic has not yet been rated - Rate this topic

about_Arithmetic_Operators

Updated: August 9, 2012

Applies To: Windows PowerShell 2.0, Windows PowerShell 3.0

TOPIC
    about_Arithmetic_Operators

SHORT DESCRIPTION
    Describes the operators that perform arithmetic in Windows PowerShell.

LONG DESCRIPTION

    Arithmetic operators calculate numeric values. You can use one or
    more arithmetic operators to add, subtract, multiply, and divide
    values, and to calculate the remainder (modulus) of a division operation.

    In addition, the addition operator (+) and multiplication operator (*)
    also operate on strings, arrays, and hash tables. The addition operator
    concatenates the input. The multiplication operator returns multiple copies
    of the input. You can even mix object types in an arithmetic statement.
    The method that is used to evaluate the statement is determined by the type
    of the leftmost object in the expression.

    Beginning in Windows PowerShell 2.0, all arithmetic operators work
    on 64-bit numbers. 

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



    Windows PowerShell supports the following arithmetic operators:


    Operator  Description                             Example
    --------  -----------                             -------
    +         Adds integers; concatenates strings,    6+2
              arrays, and hash tables.                "file" + "name"

    -         Subtracts one value from another        6-2
              value.                                  (get-date).date - 1

    -         Makes a number a negative number.       -6+2
                                                      -4
 
    *         Multiplies integers; copies strings     6*2
              and arrays the specified number of      "w" * 3
              times.

    /         Divides two values.                     6/2

    
    %         Returns the remainder of a division     7%2
              operation.
 
    -shl      Shift-left                              100 -shl 2

    -shr      Shift-right                             100 -shr 1




    OPERATOR PRECEDENCE
    Windows PowerShell processes arithmetic operators in the following order:

        Parentheses ()
        - (for a negative number)
        *, /, %
        +, - (for subtraction)


    Windows PowerShell processes the expressions from left to right according
    to the precedence rules. The following examples show the effect of the
    precedence rules: 

        C:\PS> 3+6/3*4 
        11

        C:\PS> 10+4/2
        12

        C:\PS> (10+4)/2
        7

        C:\PS> (3+3)/ (1+1)
        3
 
    The order in which Windows PowerShell evaluates expressions might differ 
    from other programming and scripting languages that you have used. The 
    following example shows a complicated assignment statement.

        C:\PS> $a = 0
        C:\PS> $b = 1,2
        C:\PS> $c = -1,-2
        
        C:\PS> $b[$a] = $c[$a++]
        
        C:\PS> $b
        1
        -1

    In this example, the expression $a++ is evaluated before $c[$a++]. 
    Evaluating $a++ changes the value of $a. The variable $a in $b[$a] 
    equals 1, not 0, so the statement assigns a value to $b[1], not $b[0].

    DIVISION AND ROUNDING
    When the quotient of a division operation is an integer, Windows
    PowerShell rounds the value to the nearest integer. When the value
    is .5, it rounds to the nearest even integer.

    The following example shows the effect of rounding to the nearest 
    even integer.


        C:\PS> [int]( 5 / 2 )
        2

        C:\PS> [int]( 7 / 2 )
        4

    ADDING AND MULTIPLYING NON-NUMERIC TYPES
    You can add numbers, strings, arrays, and hash tables. And, you can
    multiply numbers, strings, and arrays. However, you cannot multiply hash
    tables.

    When you add strings, arrays, or hash tables, the elements are 
    concatenated. When you concatenate collections, such as arrays or hash
    tables, a new object is created that contains the objects from both
    collections. If you try to concatenate hash tables that have the same key,
    the operation fails.

    For example, the following commands create two arrays and then add them:


C:\PS> $a = 1,2,3
C:\PS> $b = "A","B","C"
C:\PS> $a + $b
1
2
3
A
B
C
 

    You can also perform arithmetic operations on objects of different types. 
    The operation that Windows PowerShell performs is determined by the
    Microsoft .NET Framework type of the leftmost object in the operation.
    Windows PowerShell tries to convert all the objects in the operation to the
    .NET Framework type of the first 
    object. If it succeeds in converting the objects, it performs the operation
    appropriate to the .NET Framework type of the first object. If it fails to 
    convert any of the objects, the operation fails. 

    The following example demonstrates the use of the addition and 
    multiplication operators in operations that include different object types:


        C:\PS> "file" + 16
        file16

        C:\PS> $array = 1,2,3
        C:\PS> $array + 16
        1
        2
        3
        16

C:\PS> $array + "file"
        1
        2
        3
        file

        C:\PS> "file" * 3
        filefilefile
 
    Because the method that is used to evaluate statements is determined by the
    leftmost object, addition and multiplication in Windows PowerShell are not
    strictly commutative. For example, (a + b) does not always equal (b + a), 
    and (a * b) does not always equal (b * a).

    The following examples demonstrate this principle:

        C:\PS> "file" + 2
        file2

        C:\PS> 2 + "file"
        Cannot convert value "file" to type "System.Int32". Error: "Input
        string was not in a correct format."
        At line:1 char:4
        + 2 + <<<<  "file"

        C:\PS> "file" * 3
        filefilefile

        C:\PS> 3 * "file"
        Cannot convert value "file" to type "System.Int32". Error: "Input 
        string was not in a correct format."
        At line:1 char:4
        + 3 * <<<<  "file"
 

    Hash tables are a slightly different case. You can add hash tables. And,
    you can add a hash table to an array. However, you cannot add any other 
    type to a hash table. 

    The following examples show how to add hash tables to each other and to 
    other objects:


        C:\PS> $hash1 = @{a=1; b=2; c=3}
        C:\PS> $hash2 = @{c1="Server01"; c2="Server02"}
        C:\PS> $hash1 + $hash2

        Name                           Value
        ----                           -----
        c2                             Server02
        a                              1
        b                              2
        c1                             Server01
        c                              3


        C:\PS> $hash1 + 2
        You can add another hash table only to a hash table.
        At line:1 char:9
        + $hash1 + <<<<  2


        C:\PS> 2 + $hash1
        Cannot convert "System.Collections.Hashtable" to "System.Int32".
        At line:1 char:4
        + 2 + <<<<  $hash1
 

    The following examples demonstrate that you can add a hash table to an 
    array. The entire hash table is added to the array as a single object.


        C:\PS> $array = 1,2,3
        C:\PS> $array + $hash1
        1
        2
        3

        Name                           Value
        ----                           -----
        a                              1
        b                              2
        c                              3


        C:\PS> $sum = $array + $hash1
        C:\PS> $sum.count
        4

        C:\PS> $sum[3]
        Name                           Value
        ----                           -----
        a                              1
        b                              2
        c                              3


        PS C:\ps-test> $sum + $hash2
        1
        2
        3

        Name                           Value
        ----                           -----
        a                              1
        b                              2
        c                              3
        c2                             Server02
 

    The following example shows that you cannot add hash tables that contain 
    the same key:

        C:\PS> $hash1 = @{a=1; b=2; c=3}
        C:\PS> $hash2 = @{c="red"}
        C:\PS> $hash1 + $hash2
        Bad argument to operator '+': Item has already been added. 
        Key in dictionary: 'c'    Key being added: 'c'.
        At line:1 char:9
        + $hash1 + <<<<  $hash2
 


    Although the addition operators are very useful, use the assignment 
    operators to add elements to hash tables and arrays. For more information
    see about_assignment_operators. The following examples use the += 
    assignment operator to add items to an array:

        C:\PS>  $array
        1
        2
        3

        C:\PS>  $array + "file"
        1
        2
        3
        file

        C:\PS>  $array
        1
        2
        3

        C:\PS>  $array += "file"
        C:\PS>  $array
        1
        2
        3
        file

        C:\PS> $hash1

        Name                           Value
        ----                           -----
        a                              1
        b                              2
        c                              3

        C:\PS> $hash1 += @{e = 5}
        C:\PS> $hash1

        Name                           Value
        ----                           -----
        a                              1
        b                              2
        e                              5
        c                              3
 

    Windows PowerShell automatically selects the .NET Framework numeric type
    that best expresses the result without losing  precision. For example:

        C:\PS> 2 + 3.1
        5.1
        C:\PS> (2). GetType().FullName
        System.Int32
        C:\PS> (2 + 3.1).GetType().FullName
        System.Double

    If the result of an operation is too large for the type, the type of the 
    result is widened to accommodate the result, as in the following example: 

        C:\PS> (512MB).GetType().FullName
        System.Int32
        C:\PS> (512MB * 512MB).GetType().FullName
        System.Double

    The type of the result will not necessarily be the same as one of the 
    operands. In the following example, the negative value cannot be cast to an
    unsigned integer, and the unsigned integer is too large to be cast to
    Int32:

        C:\PS> ([int32]::minvalue + [uint32]::maxvalue).gettype().fullname
        System.Int64

    In this example, Int64 can accommodate both types.

    The System.Decimal type is an exception. If either operand has the Decimal
    type, the result will be of the Decimal type. If the result is too large
    for the Decimal type, it will not be cast to Double. Instead, an error
    results.
    
        C:\PS> [Decimal]::maxvalue
        79228162514264337593543950335
        C:\PS> [Decimal]::maxvalue + 1
        Value was either too large or too small for a Decimal.
        At line:1 char:22
        + [Decimal]::maxvalue + <<<<  1


    ARITHMETIC OPERATORS AND VARIABLES
    You can also use arithmetic operators with variables. The operators act on 
    the values of the variables. The following examples demonstrate the use of 
    arithmetic operators with variables:

        C:\PS> $intA = 6 
        C:\PS> $intB = 4 
        C:\PS> $intA + $intB 

        10 


        C:\PS> $a = "Windows " 
        C:\PS> $b = "PowerShell " 
        C:\PS> $c = 2 
C:\PS> $a + $b + $c

        Windows PowerShell 2 


    ARITHMETIC OPERATORS AND COMMANDS
    Typically, you use the arithmetic operators in expressions with numbers, 
    strings, and arrays. However, you can also use arithmetic operators with 
    the objects that commands return and with the properties of those objects.

    The following examples show how to use the arithmetic operators in 
    expressions with Windows PowerShell commands:


C:\PS> get-date
Wednesday, January 02, 2008 1:28:42 PM


C:\PS> $day = new-timespan -day 1
C:\PS> get-date + $day
Thursday, January 03, 2008 1:34:52 PM


C:\PS> get-process | where {($_.ws * 2) -gt 50mb}
Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)     Id ProcessName
-------  ------    -----      ----- -----   ------     -- -----------
   1896      39    50968      30620   264 1,572.55   1104 explorer
  12802      78   188468      81032   753 3,676.39   5676 OUTLOOK
    660       9    36168      26956   143    12.20    988 PowerShell
    561      14     6592      28144   110 1,010.09    496 services
   3476      80    34664      26092   234 ...45.69    876 svchost
    967      30    58804      59496   416   930.97   2508 WINWORD
 

 EXAMPLES
    The following examples show how to use the arithmetic operators in 
    Windows PowerShell:

C:\PS> 1 + 1
2 

C:\PS> 1 - 1 
0 

C:\PS> -(6 + 3) 
-9 

C:\PS> 6 * 2 
12 

C:\PS> 7 / 2 
3.5 

C:\PS> 7 % 2 
1 

C:\PS> w * 3 
www 

C:\PS> 3 * "w" 
Cannot convert value "w" to type "System.Int32". Error: "Input string was not
        in a correct format." 
At line:1 char:4 
+ 3 * <<<< "w" 

PS C:\ps-test> "Windows" + " " + "PowerShell" 
Windows PowerShell 

PS C:\ps-test> $a = "Windows" + " " + "PowerShell" 
PS C:\ps-test> $a 
Windows PowerShell 

C:\PS> $a[0] 
W 

C:\PS> $a = "TestFiles.txt" 
C:\PS> $b = "C:\Logs\" 
C:\PS> $b + $a 
C:\Logs\TestFiles.txt 

C:\PS> $a = 1,2,3 
C:\PS> $a + 4 
1 
2 
3 
4 

C:\PS> $servers = @{0 = "LocalHost"; 1 = "Server01"; 2 = "Server02"} 
C:\PS> $servers + @{3 = "Server03"} 
Name Value 
---- ----- 
3 Server03 
2 Server02 
1 Server01 
0 LocalHost 

C:\PS> $servers 
Name Value 
---- ----- 
2 Server02 
1 Server01 
0 LocalHost 

C:\PS> $servers += @{3 = "Server03"} #Use assignment operator 
C:\PS> $servers 
Name Value 
---- ----- 
3 Server03 
2 Server02 
1 Server01 
0 LocalHost 


    BITWISE ARITHMETIC IN WINDOWS POWERSHELL

    Windows PowerShell supports the -shl (shift-left) and 
    -shr (shift-right) operators for bitwise arithmetic.

    These operators are introduced in Windows 
    PowerShell 3.0.


    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_arrays
    about_assignment_operators
    about_comparison_operators
    about_hash_tables
    about_operators
    about_variables
    Get-Date
    New-TimeSpan



Did you find this helpful?
(1500 characters remaining)
Thank you for your feedback
Show:
© 2014 Microsoft. All rights reserved.