PowerShell, How to provide a pipe variable? - powershell

Question

This is a high level question as the details might not be precise, as I'm not in my office but home.
I have a function that accept variables through pipe:
get-csv | myfunc
The pipe source is the fields from a .csv file.
How to define a variables and pipe into myfunc()? Would HashTable be good?
$my_pipe_variables = #{ Color = ‘Red’; Doors = 4; Convertible = $false}
$my_pipe_variables | myfunc
would that be the correct syntax?
Update:
I finally get around to try it but it is not working for me, as my myfunc accesses pipe variables directly via $_. Here is the demo:
function showThem { echo Color: $_.Color }
> [pscustomobject]#{ Color = ‘Red’; Doors = 4; Convertible = $false} | showThem
Color:
How can I make it works for myfunc, which accesses pipe variables directly via $_?

Answer 1

Import-Csv (not Get-Csv), for reading CSV data from a file, and ConvertFrom-Csv, for reading CSV data from a string, output a collection of custom objects (type [pscustomobject]) whose properties reflect the CSV data's columns.
To construct such custom objects on demand in order to simulate Import-Csv / ConvertFrom-Csv input, use the [pscustomobject] #{ <propertyName>=<value>; ... } syntax (PSv3+).
E.g., to simulate 2 rows of CSV data with columns Color, Doors,
and Convertible:
[pscustomobject] #{ Color = 'Red'; Doors = 4; Convertible = $false },
[pscustomobject] #{ Color = 'Blue'; Doors = 5; Convertible = $false } |
...
Separately, in order to make a function process input from the pipeline object by object via automatic variable $_, it must have a process { ...} block - see help topic about_Functions.
# Define the function body with a process { ... } block, which
# PowerShell automatically calls for each input object from the pipeline,
# reflected in automatic variable $_
function showThem { process { "Color: " + $_.Color } }
[pscustomobject] #{ Color = 'Red'; Doors = 4; Convertible = $false },
[pscustomobject] #{ Color = 'Blue'; Doors = 5; Convertible = $false } |
showThem
Note: In PowerShell, echo is an alias of Write-Output, whose explicit use is rarely needed; instead, the function relies on PowerShell's implicit output: the result of the string concatenation (+) implicitly becomes the function's output.
The above yields:
Color: Red
Color: Blue