A hashtable is a data structure, similar to an array but you store each object using a key. It’s stored as key/value pairs in a hash table. The key and value can be any object type. Commonly, we used integers or strings as keys in the hash table.
In this article, we will discuss PowerShell hashtables, and how to declare and use them in PowerShell.
How to Declare a HashTable in PowerShell
To declare a hashtable in PowerShell, use the @{} syntax. It will create an empty hashtable.
# Creating a hashtable
$students = @{}
How to Create Hashtable with Values
To create a hashtable with values, you can pre-populate the keys and values when you create a hashtable.
The following script creates a hashtable $studentsPercentage and stores the student’s name as keys and percentage as values in the hashtable.
# pre-populate the key-value pairs in hashtable
$studentsPercentage = @{
Tom = 89
Akshada = 75
}
The output of the above script is:
PS D:\ps> $studentsPercentage
Name Value
---- -----
Akshada 75
Tom 89How to Add Items to a HashTable in PowerShell
To add items to a hashtable, use the Add() method.
# Create a hashtable
$students = @{}
# Add items to a hashtable
$students.Add(1, "Tom")
$students.Add(2, "Akshada")
$students.Add(3, "Adam")
The output of the above PowerShell scripts creates a hashtable $students having Id (integer type) as the key and Name (string type) as the value stored in it.
Print the hashtable to see the key/value pairs stored in it.
PS D:\ps> $students
Name Value
---- -----
3 Adam
2 Akshada
1 Tom
How to Get All Keys from a Hashtable in PowerShell
To get all keys from a hashtable use .keys syntax with a hashtable.
The following PowerShell script will print all the keys of a hashtable.
$students.keys
Result
PS D:\ps> $students.keys
3
2
1How to Retrieve All Values from a Hashtable in PowerShell
Use the .Values syntax with a hashtable variable to get all values from a hashtable in PowerShell.
$students.Values
Result
Adam
Akshada
TomHow to Access the Items from a Hashtable in PowerShell
To access the items from the hashtable in PowerShell, you can specify the key. It will return the value associated with the given key in a hashtable.
# retrieve data from a hashtable using the key $students[1]
The output of the above PowerShell script gets value from a hashtable by key.
PS D:\ps> $students[1]
TomHow to Loop Through a Hashtable
You can iterate a hashtable in different ways and access its key-value pairs from the collections.
$studentsPercentage.GetEnumerator() | ForEach-Object{
$msg = 'Student {0} has scored {1} percentages'
Write-Output $msg
}
In the above PowerShell script, the GetEnumerator() method is used for iterating over the hashtable the $studentsPercentage. The enumerator gets each key/value pair from the collection and pipes it to the ForEach-Object loop for iteration.
The output of the above PowerShell script is given below.
Student Akshada has scored 75 percentages
Student Tom has scored 89 percentages
You can enumerate the keys of the hashtable and use them to access the values.
$students.Keys | ForEach-Object
{
Write-Host "Student ID $($_) : $($students[$_])"
}
Result
PS D:\ps> $students.Keys | ForEach-Object { Write-Host "Student ID $($_) :
$($students[$_])"}
Student ID 3 : Adam
Student ID 2 : Akshada
Student ID 1 : Tom
PS D:\ps> How to Update Hashtable Values
To update the hashtable values, use the key to select the key/value pair.
$studentsPercentage['Akshada'] = 77
In the above PowerShell script, we have used the index (key) to update the $studentsPercentage hashtable value.
The output of the above script after updating hashtable values using the index is:
PS D:\ps> $studentsPercentage
Name Value
---- -----
Akshada 75
Tom 89
PS D:\ps> $studentsPercentage['Akshada'] = 77 PS D:\ps> $studentsPercentage
Name Value
---- -----
Akshada 77
Tom 89
PS D:\ps> How to Remove Keys from a Hashtable Using PowerShell
To remove a key/value pair from a hashtable, you can use the .remove() method.
The following script deletes keys from a hashtable as specified in the remove() method.
$studentsPercentage.Remove('Akshada')
The above command will remove a key named ‘Akshada‘ from a hashtable $studentsPercentage.
How to Clear a Hashtable Using PowerShell
To clear a hashtable using the PowerShell, use the Clear() method. The Clear() will remove all key/value pairs from a hash table.
$studentsPercentage.Clear()
How to Sort a Hashtable Using PowerShell
To sort a hashtable by its key (index) in a PowerShell, enumerate the keys in a hash table and pipe the result to the Sort-Object cmdlet. The Sort-Object command uses the property Key to sort the hashtable by key.
$students.GetEnumerator() | Sort-Object -Property Key
Result
PS D:\ps> $students.GetEnumerator() | Sort-Object -Property Key
Name Value
---- -----
1 Tom
2 Akshada
3 Adam
PS D:\ps> Create Custom Objects From Hashtables
To create an object from the hashtable in PowerShell, use the [PSCustomObject] in front of the hash table.
$students_object = [PSCustomObject]@{
Tom = 89
Akshada = 75
}
Result
PS D:\ps> $students_object
Tom Akshada
--- -------
89 75How to Count Items in Hashtable in PowerShell
To count items in a hashtable, use the Count property.
$students.Count
Result
PS D:\ps> $students.Count
3How to Check If Hashtable Contains a Key in PowerShell
To check if a Hashtable contains a key in PowerShell, use the .ContainKey() method within the if statement.
$key = 'Tom' if($studentsPercentage.ContainsKey($key))
{
Write-Host "key $key exists in the hashtable."
} Else
{
Write-Host "key $key does not exists in the hashtable."
}
Result
key Tom exists in the hashtable.
Cool Tip: How to use array in PowerShell!
Conclusion
I hope the above article on the PowerShell hashtable topic is helpful to you.
The Hashtable is very useful when you want to store structured data. Once you have a key/value pair stored in the hashtable, you can use the GetEnumerator() method or Foreach loop well to iterate over the items or use an index to access the individual elements in the hashtable.
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