Hash Table
Hash Table
Hash table can store information as a set of keys and values.
Hash table does not guarantee the order of storage.
How to create an hash table
# Normal example
PS> $hash = @{
>> Key1 = "Value1"
>> Key2 = 1,2
>> }
PS> $hash
Name Value
---- -----
Key2 {1, 2}
Key1 Value1
# Single line example. Separated by semicolons.
PS> $hash = @{Key1 = "Value1"; Key2 = 1,2}
PS> $hash
Name Value
---- -----
Key2 {1, 2}
Key1 Value1
How to access the elements of hash table
# Property-based access methods $hash.Key
PS> $hash.Key1
Value1
PS> $hash.Key2
1
2
# Accessing elements using index $hash["Key"]
PS> $hash["Key1"]
Value1
PS> $hash["Key2"]
1
2
Adding elements to hash table
How to add keys and values.
# Property-based access methods $hash.Key = Value
PS> $hash.Key3 = "NewValue3"
PS> $hash
Name Value
---- -----
Key1 Value1
Key2 {1, 2}
Key3 NewValue3
# Accessing elements using index $hash["Key"] = Value
PS> $hash["Key4"] = "NewValue4"
PS> $hash
Name Value
---- -----
Key3 NewValue3
Key2 {1, 2}
Key1 Value1
Key4 NewValue4
Removing elements of hash table
Use the Remove method to remove an element from hash table.
PS> $hash.Remove("Key3")
PS> $hash
Name Value
---- -----
Key2 {1, 2}
Key1 Value1
Key4 NewValue4
Clearing hash table
Using the Clear method to clear hash table.
PS> $hash.Clear()
PS> $hash
PS>
Hash table with Guaranteed Order
If you want to guarantee the order in which the keys are stored, add [ordered].
Since the storage order is guaranteed, you can access by index value as in $table[number].
Available in PowerShell V3 and later.
PS> $ordered = [ordered]@{first=1;second=2}
PS> $ordered.first
1
PS> $ordered[0]
1
User-defined objects
To create a user-defined object, add [pscustomobject].
It can be sorted and selected like any other object.
Available in PowerShell V3 and later.
PS> $object = [PSCustomObject]@{Shell="PowerShell";Computer="Windows"}
PS> $object
Shell Computer
----- --------
PowerShell Windows
# Example of using a created user-defined object (CSV file output)
PS> $object | Export-CSV -Path ./object.csv
How to sort by key or value
By nature, hash tables are used to refer to values by keys.
If you still want to sort it, use GetEnumerator() method.
PS> $hash = @{key1 = 1; key2 = 2; key10 = 10; key3 = 3; key13 = 13}
PS> $hash
Name Value
---- -----
key13 13
key1 1
key2 2
key3 3
key10 10
PS> $hash.GetEnumerator() | sort value
Name Value
---- -----
key1 1
key2 2
key3 3
key10 10
key13 13
Hash table and foreach statement
To handle hash table in foreach statement, use $hash.Keys.
PS> $hash = @{key1 = 1; key2 = 2; key10 = 10; key3 = 3; key13 = 13}
PS> foreach ($key in $hash.Keys) {
>> "$($key):$($hash.$key)"
>> }
>>
key13:13
key1:1
key2:2
key3:3
key10:10
YouTube
Click here for a video explanation.
Reference Links
Everything you wanted to know about hashtables | Microsoft Docs