Construct JSON objects from multiple pipelines

Question

I've been breaking my head over this for a while now. I run two pipelines to produce two arrays of tuples. Each tuple contains a (filename, property).

# create pipeline of (file, property1) tuples
$prop1 = Get-ChildItem *.prop1 -PipelineVariable fi |
           Get-Content -Tail 150 |
           Select-String -Pattern "  Pattern1 (\d+)" | 
           ForEach-Object { $_.Matches } |
           ForEach-Object { [System.Tuple]::Create($fi.Name, $_.Groups[1].Value) }

# create pipeline of (file, property2) tuples
$prop2 = Get-ChildItem *.prop2 -PipelineVariable fi | 
           Get-Content -Tail 5 | 
           Select-String -Pattern "  Pattern2 (\d+)" | % { $_.Matches } |
           ForEach-Object { $_.Matches } | 
           ForEach-Object { [System.Tuple]::Create($fi.Name, $_.Groups[1].Value) }

$result = ????
ConvertTo-Json $result

Now I would like to combine these tuple pipelines on filename to produce JSON output like:

[
  {
     'file':'filename1',
     'prop1':'value1',
     'prop2':'value2',
  },
  {
     'file':'filename2',
     'prop1':'value3',
     'prop2':'value3',
  }
]

How can I combine these pipelines to produce the desired output? Or am I making this more complicated than necessary?

And you are sure that there's always the exact same number of tuples in $prop1 and $prop2? — Mathias R. Jessen
– Mathias R. Jessen, Commented Jun 13, 2016 at 22:42

Mathias R. Jessen · Accepted Answer · 2016-06-14 00:03:01Z

2

Instead of binding the property values to the filename with a Tuple, use a Hashtable where the filename is the key:

$FileProps = @{}
Get-ChildItem *.prop1 -PipelineVariable fi |
           Get-Content -Tail 150 |
           Select-String -Pattern "  Pattern1 (\d+)" | 
           ForEach-Object { $_.Matches } |
           ForEach-Object { $FileProps[$fi.BaseName] = @{ 'filename' = $fi.BaseName; 'prop1' = $_.Groups[1].Value }}

Get-ChildItem *.prop2 -PipelineVariable fi | 
           Get-Content -Tail 5 | 
           Select-String -Pattern "  Pattern2 (\d+)" | % { $_.Matches } |
           ForEach-Object { $_.Matches } | 
           ForEach-Object { $FileProps[$fi.BaseName]['prop2'] = $_.Groups[1].Value }

Now create a bunch of custom objects based on the hashtable entries and convert them to json:

$Json = $FileProps.Keys |ForEach-Object {
    New-Object psobject -Property $FileProps[$_]
} |ConvertTo-Json

answered Jun 14, 2016 at 0:03

Mathias R. Jessen

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1 Comment

MvdD Over a year ago

Thanks, this works! I could not get the nested hashtable right.

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