Getting the current hash key in a ForEach-Object loop in powershell

Question

I've got a hash table:

$myHash = @{ 
   "key1" = @{
       "Entry 1" = "one"
       "Entry 2" = "two"
   }
   "key 2" = @{
       "Entry 1" = "three"
       "Entry 2" = "four"
   }
}

I'm doing a loop through to get the objects:

$myHash.keys | ForEach-Object {
    Write-Host $_["Entry 1"]
}

Works fine, but what can I use to figure out which of the keys of $myHash I'm in? $_.Name doesn't return anything. I'm stumped. Help?

Solution 1

I like to use GetEnumerator() when looping a hashtable. It will give you a property value with the object, and a property key with it's key/name. Try:

$myHash.GetEnumerator() | % { 
    Write-Host "Current hashtable is: $($_.key)"
    Write-Host "Value of Entry 1 is: $($_.value["Entry 1"])" 
}

Solution 2

You can also do this without a variable

@{
  'foo' = 222
  'bar' = 333
  'baz' = 444
  'qux' = 555
} | % getEnumerator | % {
  $_.key
  $_.value
}

Solution 3

here a similare function i used to read ini file.(the value are also a dictionary like yours).

ini file that i transform into hash look like this

[Section1]

key1=value1
key2=value2

[Section2]

key1=value1
key2=value2
key3=value3

From the ini the hashtable look like this (i passed the fonction that do the transformation in to hash):

$Inihash = @{ 
           "Section1" = @{
               "key1" = "value1"
               "key2" = " value2"
           }
           "Section2" = @{
               "key1" = "value1"
               "key2" = "value2"
         "key3" = "value3"
           }
        }

so from the hash table this line will search all the key/value for a given section:

$Inihash.GetEnumerator() |?{$_.Key -eq "Section1"} |% {$_.Value.GetEnumerator() | %{write-host $_.Key "=" $_.Value}} 

? = for search where-object equal my section name. % = you have to do 2 enumeration ! one for all the section and a second for get all the key in the section.

Comments

[Matt Simmons]

OK, so I initially left out the ".keys" part of $myHash.keys in the loop both here and in my testing window, even though they were in the actual script. As it turns out, specifying the .keys value does cause it to work. But Graimer's code works too, even with my original mistake, so he gets the checkmark.

[Matt Simmons]

Thanks! I appreciate it. Works well!

[Jake H]

Another common way is: $hash.Keys | %{ "key is: $($_), value is $($hash[$_])" }

[Frode F.]

It does the same, but requires multiple reads to the hashtable and is more prone to typos

[Joshua K]

Good use of the pipeline and demonstration of nesting. Thanks! This is an excellent example of the power of powershell.