CMD or Powershell to concatenate (concatenate) matching lines from two files

In PowerShell and assuming both files have exactly the same number of lines:

$f1 = Get-Content file1
$f2 = Get-Content file2

for ($i = 0; $i -lt $f1.Length; ++$i) {
  $f1[$i] + "`t" + $f2[$i]
}

      

        
        
        
      

    

A generalized solution that supports multiple files , based on a beautiful, efficient memory addressingSystem.IO.StreamReader

by Ansgar Wiechers :

PowerShell's ability to call items (properties, methods) directly on a collection and automatically call them for all items in the collection ( member enumeration , v3 +) makes it easy to generalize:

# Make sure .NET has the same current dir. as PS.
[System.IO.Directory]::SetCurrentDirectory($PWD)

# The input file paths.
$files = 'file1', 'file2', 'file3'

# Create stream-reader objects for all input files.
$readers = [IO.StreamReader[]] $files

# Keep reading while at least 1 file still has more lines.
while ($readers.EndOfStream -contains $false) {

  # Read the next line from each stream (file).
  # Streams that are already at EOF fortunately just return "".
  $lines = $readers.ReadLine()

  # Output the lines separated with tabs.
  $lines -join "'t"

}

# Close the stream readers.
$readers.Close()

      

        
        
        
      

    

Get-MergedLines

(source code below; called from -?

For Reference) wraps the functionality into a function that:

• accepts a variable number of filenames - both as an argument and via a pipeline

• uses a custom delimiter to concatenate lines (tab by default)

• allows you to trim end instances of the delimiter

function Get-MergedLines() {
<#
.SYNOPSIS
Merges lines from 2 or more files with a specifiable separator (default is tab).

.EXAMPLE
> Get-MergedLines file1, file2 '<->'

.EXAMPLE
> Get-ChildItem file? | Get-MergedLines
#>
  param(
    [Parameter(Mandatory, ValueFromPipeline, ValueFromPipelineByPropertyName)]
    [Alias('PSPath')]
    [string[]] $Path,

    [string] $Separator = "'t",

    [switch] $TrimTrailingSeparators
  )

  begin { $allPaths = @() }

  process { $allPaths += $Path }

  end {

    # Resolve all paths to full paths, which may include wildcard resolution.
    # Note: By using full paths, we needn't worry about .NET current dir.
    #       potentially being different.
    $fullPaths = (Resolve-Path $allPaths).ProviderPath

    # Create stream-reader objects for all input files.
    $readers = [System.IO.StreamReader[]] $fullPaths

    # Keep reading while at least 1 file still has more lines.
    while ($readers.EndOfStream -contains $false) {

      # Read the next line from each stream (file).
      # Streams that are already at EOF fortunately just return "".
      $lines = $readers.ReadLine()

      # Join the lines.
      $mergedLine = $lines -join $Separator

      # Trim (remove) trailing separators, if requested.
      if ($TrimTrailingSeparators) {
        $mergedLine = $mergedLine -replace ('^(.*?)(?:' + [regex]::Escape($Separator) + ')+$'), '$1'
      }

      # Output the merged line.
      $mergedLine

    }

    # Close the stream readers.
    $readers.Close()

  }

}

      

        
        
        
      

    

Powershell solution:

$file1 = Get-Content file1
$file2 = Get-Content file2
$outfile = "file3.txt"

for($i = 0; $i -lt $file1.length; $i++) {
  "$($file1[$i])`t$($file2[$i])" | out-file $outfile -Append 
}