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PowerShell proxy cmdlet – function which wraps standard Export-CSV cmdlet but adds handling of the -Append parameter
#Requires -Version 2.0
<#
This Export-CSV behaves exactly like native Export-CSV
However it has one optional switch -Append
Which lets you append new data to existing CSV file: e.g.
Get-Process | Select ProcessName, CPU | Export-CSV processes.csv -Append
For details, see
http://dmitrysotnikov.wordpress.com/2010/01/19/export-csv-append/
(c) Dmitry Sotnikov
#>
function Export-CSV {
[CmdletBinding(DefaultParameterSetName='Delimiter',
SupportsShouldProcess=$true, ConfirmImpact='Medium')]
param(
[Parameter(Mandatory=$true, ValueFromPipeline=$true,
ValueFromPipelineByPropertyName=$true)]
[System.Management.Automation.PSObject]
${InputObject},
[Parameter(Mandatory=$true, Position=0)]
[Alias('PSPath')]
[System.String]
${Path},
#region -Append (added by Dmitry Sotnikov)
[Switch]
${Append},
#endregion
[Switch]
${Force},
[Switch]
${NoClobber},
[ValidateSet('Unicode','UTF7','UTF8','ASCII','UTF32','BigEndianUnicode','Default','OEM')]
[System.String]
${Encoding},
[Parameter(ParameterSetName='Delimiter', Position=1)]
[ValidateNotNull()]
[System.Char]
${Delimiter},
[Parameter(ParameterSetName='UseCulture')]
[Switch]
${UseCulture},
[Alias('NTI')]
[Switch]
${NoTypeInformation})
begin
{
# This variable will tell us whether we actually need to append
# to existing file
$AppendMode = $false
try {
$outBuffer = $null
if ($PSBoundParameters.TryGetValue('OutBuffer', [ref]$outBuffer))
{
$PSBoundParameters['OutBuffer'] = 1
}
$wrappedCmd = $ExecutionContext.InvokeCommand.GetCommand('Export-Csv',
[System.Management.Automation.CommandTypes]::Cmdlet)
#String variable to become the target command line
$scriptCmdPipeline = ''
# Add new parameter handling
#region Dmitry: Process and remove the Append parameter if it is present
if ($Append) {
$PSBoundParameters.Remove('Append') | Out-Null
if ($Path) {
if (Test-Path $Path) {
# Need to construct new command line
$AppendMode = $true
if ($Encoding.Length -eq 0) {
# ASCII is default encoding for Export-CSV
$Encoding = 'ASCII'
}
# For Append we use ConvertTo-CSV instead of Export
$scriptCmdPipeline += 'ConvertTo-Csv -NoTypeInformation '
# Inherit other CSV convertion parameters
if ( $UseCulture ) {
$scriptCmdPipeline += ' -UseCulture '
}
if ( $Delimiter ) {
$scriptCmdPipeline += " -Delimiter '$Delimiter' "
}
# Skip the first line (the one with the property names)
$scriptCmdPipeline += ' | Foreach-Object {$start=$true}'
$scriptCmdPipeline += '{if ($start) {$start=$false} else {$_}} '
# Add file output
$scriptCmdPipeline += " | Out-File -FilePath '$Path' -Encoding '$Encoding' -Append "
if ($Force) {
$scriptCmdPipeline += ' -Force'
}
if ($NoClobber) {
$scriptCmdPipeline += ' -NoClobber'
}
}
}
}
$scriptCmd = {& $wrappedCmd @PSBoundParameters }
if ( $AppendMode ) {
# redefine command line
$scriptCmd = $ExecutionContext.InvokeCommand.NewScriptBlock(
$scriptCmdPipeline
)
} else {
# execute Export-CSV as we got it because
# either -Append is missing or file does not exist
$scriptCmd = $ExecutionContext.InvokeCommand.NewScriptBlock(
[string]$scriptCmd
)
}
# standard pipeline initialization
$steppablePipeline = $scriptCmd.GetSteppablePipeline($myInvocation.CommandOrigin)
$steppablePipeline.Begin($PSCmdlet)
} catch {
throw
}
}
process
{
try {
$steppablePipeline.Process($_)
} catch {
throw
}
}
end
{
try {
$steppablePipeline.End()
} catch {
throw
}
}
<#
.ForwardHelpTargetName Export-Csv
.ForwardHelpCategory Cmdlet
#>
}
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