install-dotnet-core.ps1

# From the FV buil script:

target install-dotnet-core {
  # Version check as $IsWindows, $IsLinux etc are not defined in PS 5, only PS Core.
  $win = (($PSVersionTable.PSVersion.Major -le 5) -or $IsWindows)
  $json = ConvertFrom-Json (Get-Content "$path/global.json" -Raw)
  $required_version = $json.sdk.version
  # If there's a version mismatch with what's defined in global.json then a 
  # call to dotnet --version will generate an error. AppVeyor vs local seem to have different
  # behaviours handling exit codes (appveyor will immediately halt execution on windows, but not linux)
  # so the simplest workaround is to write the output to a file and read it back rathre than rely on exit codes. 
  try { dotnet --version 2>&1>$null } catch { $install_sdk = $true }
  
  if ($global:LASTEXITCODE) {
    $install_sdk = $true;
    $global:LASTEXITCODE = 0;
  }

  if ($install_sdk) {
    $installer = $null;
    if ($win) {
      $installer = "$path/dotnet-installer.ps1" 
      (New-Object System.Net.WebClient).DownloadFile("https://dot.net/v1/dotnet-install.ps1", $installer);
    }
    else { 
      $installer = "$path/dotnet-installer"
      (New-Object System.Net.WebClient).DownloadFile("https://dot.net/v1/dotnet-install.sh", $installer); 
      chmod +x dotnet-installer
    }

    # Extract the channel from the minimum required version.
    $bits = $json.sdk.version.split(".")
    $channel = $bits[0] + "." + $bits[1];
    Write-Host Installing $json.sdk.version from $channel
    . $installer -i "$path/.dotnetsdk" -c $channel -v $json.sdk.version

    # Collect installed SDKs.
    $sdks = & "$path/.dotnetsdk/dotnet" --list-sdks | ForEach-Object { 
      $version = $_.Split(" ")[0].Split(".")
      $version[0] + "." + $version[1];
    }
    
    # Install any other SDKs required. Only bother installing if not installed already. 
    $json.others.PSObject.Properties | Foreach-Object {
      if (!($sdks -contains $_.Name)) {
        Write-Host Installing $_.Value from $_.Name
        . $installer -i "$path/.dotnetsdk" -c $_.Name -v $_.Value
      }
    }
  }
}

target find-sdk {
  if (Test-Path "$path/.dotnetsdk") {
    Write-Host "Using .NET SDK from $path/.dotnetsdk"
    $env:DOTNET_INSTALL_DIR = "$path/.dotnetsdk"

    if (($PSVersionTable.PSVersion.Major -le 5) -or $IsWindows) {
      $env:PATH = "$env:DOTNET_INSTALL_DIR;$env:PATH"
    }
    else {
      # Linux uses colon not semicolon, so can't use string interpolation
      $env:PATH = $env:DOTNET_INSTALL_DIR + ":" + $env:PATH
    }
  }
}