Looping through a hash or using an array in PowerShell

Question

I m using this  simplified  chunk of code to extract a set of tables from SQL Server with BCP    OutputDirectory    c  junk    ServerOption      -SServerName   TargetDatabase    Content dbo     ExtractTables           Page         ChecklistItemCategory         ChecklistItem     for   i 0   i -le  ExtractTables Length     1   i            InputFullTableName     TargetDatabase   ExtractTables  i         OutputFullFileName     OutputDirectory   ExtractTables  i        bcp  InputFullTableName out  OutputFullFileName -T -c  ServerOption     It works great  but now some of the tables need to be extracted via views  and some don t  So I need a data structure something like this    Page                        vExtractPage     ChecklistItemCategory     ChecklistItemCategory     ChecklistItem             vExtractChecklistItem    I was looking at hashes  but I m not finding anything on how to loop through a hash  What would be the right thing to do here  Perhaps just use an array  but with both values  separated by space   Or am I missing something obvious

User · Answer

A short traverse could be given too using the sub-expression operator $( ), which returns the result of one or more statements.

$hash = @{ a = 1; b = 2; c = 3}

forEach($y in $hash.Keys){
    Write-Host "$y -> $($hash[$y])"
}

Result:

a -> 1
b -> 2
c -> 3

User · Answer

I prefer this variant on the enumerator method with a pipeline  because you don t have to refer to the hash table in the foreach  tested in PowerShell 5     hash           a    3      b    2      c    1    hash getEnumerator     foreach       Write-Host   Key          key     and Value          value       Output   Key   c and Value   1 Key   b and Value   2 Key   a and Value   3   Now  this has not been deliberately sorted on value  the enumerator simply returns the objects in reverse order   But since this is a pipeline  I now can sort the objects received from the enumerator on value    hash getEnumerator     sort-object -Property value -Desc   foreach     Write-Host   Key          key     and Value          value       Output   Key   a and Value   3 Key   b and Value   2 Key   c and Value   1

User · Answer

Here is another quick way  just using the key as an index into the hash table to get the value    hash           a    1       b    2       c    3     foreach  key in  hash keys        Write-Host   Key        key     and Value        hash  key

User · Answer

If you re using PowerShell v3  you can use JSON instead of a hashtable  and convert it to an object with Convert-FromJson                      FileName    Page           ObjectName    vExtractPage                        ObjectName    ChecklistItemCategory                        ObjectName    ChecklistItem                      Convert-FromJson       ForEach-Object            InputFullTableName     0  1   -f  TargetDatabase    ObjectName            In strict mode  you can t reference a property that doesn t exist            so check if it has an explicit filename firest           outputFileName      ObjectName         if       Get-Member FileName                          outputFileName      FileName                    OutputFullFileName   Join-Path  OutputDirectory  outputFileName          bcp  InputFullTableName out  OutputFullFileName -T -c  ServerOption

User · Answer

About looping through a hash    Q      ONE   1   TWO   2   THREE   3    Q GETENUMERATOR            VALUE   1 3 2   Q GETENUMERATOR            key   ONE THREE TWO

User · Answer

Shorthand is not preferred for scripts  it is less readable  The     operator is considered shorthand  Here s how it should be done in a script for readability and reusability  Variable Setup PS gt   hash          a   1     b   2     c   3   PS gt   hash  Name                           Value ----                           ----- c                              3 b                              2 a                              1  Option 1  GetEnumerator   Note  personal preference  syntax is easier to read The GetEnumerator   method would be done as shown  foreach   h in  hash GetEnumerator          Write-Host  quot    h Name      h Value  quot     Output  c  3 b  2 a  1  Option 2  Keys The Keys method would be done as shown  foreach   h in  hash Keys        Write-Host  quot   h      hash Item  h   quot     Output  c  3 b  2 a  1  Additional information Be careful sorting your hashtable    Sort-Object may change it to an array  PS gt   hash GetType    IsPublic IsSerial Name                                     BaseType -------- -------- ----                                     -------- True     True     Hashtable                                System Object   PS gt   hash    hash GetEnumerator     Sort-Object Name PS gt   hash GetType    IsPublic IsSerial Name                                     BaseType -------- -------- ----                                     -------- True     True     Object                                   System Array   This and other PowerShell looping are available on my blog

User · Answer

You can also do this without a variable        foo    222    bar    333    baz    444    qux    555       getEnumerator            key      value

User · Answer

Christian s answer works well and shows how you can loop through each hash table item using the GetEnumerator method  You can also loop through using the keys property  Here is an example how    hash          a   1     b   2     c   3    hash Keys        key        value        hash Item         Output   key   c   value   3 key   a   value   1 key   b   value   2

[powershell] Looping through a hash, or using an array in PowerShell

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