Describes how to create, use, and sort hash tables in Windows PowerShell. (about_hash_tables)
TOPICabout_Hash_TablesSHORT DESCRIPTIONDescribes how to create, use, and sort hash tables in Windows PowerShell.LONG DESCRIPTIONA hash table, also known as a dictionary or associative array, is a compact data structure that stores one or more name/value pairs. For example, a hash table might contain a series of names and employee IDs, computer names and IP addresses, or message IDs and message text. Hash tables are frequently used because they are very efficient for finding and retrieving data. You can use hash tables to store lists and to create calculated properties in Windows PowerShell. And, Windows PowerShell has a cmdlet, ConvertFrom-StringData, that converts strings to a hash table. Creating Hash Tables The items in a hash table are arranged in name/value pairs, such as: Msg1="Please enter your password." Msg2="The path parameter is required." Msg3="The alias of Get-Command is gcm." The values are mapped to or associated with the names so that when you submit the name, Windows PowerShell returns the value. In Windows PowerShell, the syntax of a hash table is as follows: @{ <name> = <value>; [<name> = <value> ] ...} When you create a hash table, follow these guidelines: - Begin the hash table with an at sign (@). - Enclose the hash table in braces ({}). - Enter one or more name-value pairs for the content of the hash table. - Use an equal sign (=) to separate each name from its value. - Use a semicolon (;) to separate the name/value pairs. - If a name or value contains spaces, enclose it in quotation marks. For example, a hash table of the previous user messages looks like this: @{ Msg1="Please enter your password."; Msg2="The path parameter is required."; Msg3="The alias of Get-Command is gcm."; } To use a hash table in scripts and commands, save it in a variable. The value of the variable is a hash table object (System.Collections.Hashtable), and each name in the name/value pairs is a property of the hash table object. The following commands save the user-message hash table in the $a variable and use the dot method to display the values. C:\PS> $a = @{ >> Msg1="Please enter your password."; >> Msg2="The path parameter is required."; >> Msg3="The alias of Get-Command is gcm."; >> } C:\PS> $a Name Value ---- ----- Msg1 Please enter your password. Msg3 The alias of Get-Command is gcm. Msg2 The path parameter is required. C:\PS> $a.Msg1 Please enter your password. Hash tables are not limited to one type of data. You can enter any data type in a hash table, and you can combine data types in a single hash table. For example, you can build a hash table that contains an integer, a call to a cmdlet, and a string. Sorting Hash Tables To sort the hash table alphabetically by keys or values, use the GetEnumerator method of hash tables to get the keys and values in the hash table, and then use the Sort-Object cmdlet to sort them. For example, the following command sorts the hash table in $a alphabetically by keys. C:\PS> $a.getenumerator() | sort-object -property key Name Value ---- ----- Msg1 Please enter your password. Msg2 The path parameter is required. Msg3 The alias of Get-Command is gcm. The following command uses the same method to sort the hash values in descending order. C:\PS> $a.getenumerator() | sort-object -property value -descending Name Value ---- ----- Msg2 The path parameter is required. Msg3 The alias of Get-Command is gcm. Msg1 Please enter your password. ConvertFrom-StringData The ConvertFrom-StringData cmdlet converts a string or a here-string of name/value pairs into a hash table. You can use the ConvertFrom-StringData cmdlet safely in the Data section of a script, and you can use it with the Import-LocalizedData cmdlet to display user messages in the user-interface (UI) culture of the current user. Here-strings are especially useful when the values in the hash table include quotation marks. (For more information about here-strings, see about_Quoting_Rules.) The following example shows how to create a here-string of the user messages in the previous example and how to use ConvertFrom-StringData to convert them from a string into a hash table. The following command creates a here-string of the name/value pairs and then saves it in the $string variable. C:\PS> $string = @" Msg1="Please enter your password." Msg2="The path parameter is required." Msg3="The alias of Get-Command is gcm." "@ This command uses the ConvertFrom-StringData cmdlet to convert the here-string into a hash table. C:\PS> convertfrom-stringdata $string Name Value ---- ----- Msg3 "The alias of Get-Command is gcm." Msg2 "The path parameter is required." Msg1 "Please enter your password." SEE ALSO about_Arrays about_Quoting_Rules about_Script_Internationalization ConvertFrom-StringData Import-LocalizedData C:\Windows>powershell get-help about_History -full
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