Merge multiple csv file with same header using powershell

February 8, 2023

I am having multiple csv files in a folder with data like below

file1

"Index","Response","Status","Time"
"32190","2","Succeeded","2023-01-18 08:31:34.9"
"32189","3","Succeeded","2023-01-18 08:26:34.9"
"32188","3","Succeeded","2023-01-18 08:21:34.9"

file2

"Index","Response","Status","Time"
"32190","2","Succeeded","2023-01-19 08:31:34.9"
"32189","3","Succeeded","2023-01-19 08:26:34.9"
"32188","3","Succeeded","2023-01-19 08:21:34.9"

Need to merge these files into a single csv with a one header

"Index","Response","Status","Time"
"32190","2","Succeeded","2023-01-18 08:31:34.9"
"32189","3","Succeeded","2023-01-18 08:26:34.9"
"32188","3","Succeeded","2023-01-18 08:21:34.9"
"32190","2","Succeeded","2023-01-19 08:31:34.9"
"32189","3","Succeeded","2023-01-19 08:26:34.9"
"32188","3","Succeeded","2023-01-19 08:21:34.9"

I have this below code but I am not able to get single header in it

$folder = 'D:\reports\daily_csv' 
$files = Get-ChildItem $folder\*.csv 
Get-Content $files | Set-Content "D:\Monthly\Merged_$prev_month.csv"

Please let me know what I need to add here to avoid multiple headers

>Solution :

Here is one way to do it using StreamReader and an anonymous function. Note that .OpenText() initializes the StreamReader with UTF8 encoding, if that’s a problem you can use StreamReader(String, Encoding) instead.

$folder = 'D:\reports\daily_csv'
Get-ChildItem $folder\*.csv | & {
    begin { $isFirstObject = $true }
    process {
        try {
            $reader  = $_.OpenText()
            $headers = $reader.ReadLine()

            if($isFirstObject) {
                $headers
                $isFirstObject = $false
            }

            while(-not $reader.EndOfStream) {
                $reader.ReadLine()
            }
        }
        finally {
            if($reader) {
                $reader.Dispose()
            }
        }
    }
} | Set-Content path\to\mergedCsv.csv