PowerShell's Clear-History doesn't clear history

On Windows 10, the history and sensitive data show up again in future sessions, even after Alt+F7 and clear-history. It turns out the history is stored in a text file found at:

(Get-PSReadlineOption).HistorySavePath

I delete the offending line from that file or delete the whole file, and then end the current session or clear it via CB's answer


To complement CB.'s helpful answer and JVimes's helpful answer:

  • PowerShell's own history mechanism (Get-History, Clear-History) is host-independent, which is why - somewhat unexpectedly - you also need to clear the hosts's command history separately.

  • As for the console host's own history feature:

    • doskey-style history feature, before module PSReadline shipped with PowerShell (see below):

      • There is no saved history - a history is kept only for the duration of the current session.
      • Alt+F7 must be used to clear the console's history, with no (obvious) programmatic way to do it (in a cmd.exe console window you could use doskey /reinstall, but that doesn't work in PS).
      • CB.'s answer shows you how to simulate this keyboard combination; remember: this must be used in addition to Clear-History.

    • The PSReadline module comes with PowerShell v5 on Windows 10 and will also ship with Windows Server 2016; it replaces the doskey-style line-editing and command-history features with more sophisticated functionality; it is also possible to retrofit older Windows editions / PS versions (>= v3) versions with it, using the PowerShell Gallery (PSv3 and PSv4 must first install PowerShellGet).

      • Command history is now saved across sessions, in file
        (Get-PSReadlineOption).HistorySavePath.
      • [Microsoft.PowerShell.PSConsoleReadLine]::ClearHistory() can be used to clear the current session's history (note that v1.2+ also supports Alt+F7 for interactive clearing of the current history).
        • CAVEAT: With PSReadline's default history-saving style, SaveIncrementally, any sensitive commands have already been saved by the time to you call [Microsoft.PowerShell.PSConsoleReadLine]::ClearHistory(), and will reappear in the next session.
        • The only way to handle this is to remove the saved-history file, as demonstrated in JVimes's answer which, however, invariably wipes out the entire history.
        • IF you set up your profile to call Set-PSReadlineOption -HistorySaveStyle SaveAtExit every time a session starts - the setting apparenly does NOT "stick" by itself - you should be able to get away with only calling [Microsoft.PowerShell.PSConsoleReadLine]::ClearHistory() (in addition to Clear-History) without also having to delete the saved-history file, in which case you won't lose your saved history from previous sessions. HOWEVER, AS OF v1.2, SaveAtExit is BROKEN ALTOGETHER - no history is saved at all; see https://github.com/lzybkr/PSReadLine/issues/262

The following advanced function bundles all commands necessary to clear the command history (both for PowerShell itself and the console), both for doskey-style and PSReadline-module PowerShell console windows:

Note:

  • Because it's (currently) the only safe option, PSReadline's saved-history file is deleted as well, which means the entire history, including from previous sessions, is cleared.

  • Therefore, a confirmation prompt is shown by default.

<#
# .SYNOPSIS
#  Clears the command history, including the saved-to-file history, if applicable.
#>
function Clear-SavedHistory {
  [CmdletBinding(ConfirmImpact='High', SupportsShouldProcess)]
  param(    
  )

  # Debugging: For testing you can simulate not having PSReadline loaded with
  #            Remove-Module PSReadline -Force
  $havePSReadline = ($null -ne (Get-Module -EA SilentlyContinue PSReadline))

  Write-Verbose "PSReadline present: $havePSReadline"

  $target = if ($havePSReadline) { "entire command history, including from previous sessions" } else { "command history" } 

  if (-not $pscmdlet.ShouldProcess($target))
  {
        return
  }

  if ($havePSReadline) {

    Clear-Host

    # Remove PSReadline's saved-history file.
    if (Test-Path (Get-PSReadlineOption).HistorySavePath) { 
      # Abort, if the file for some reason cannot be removed.
      Remove-Item -EA Stop (Get-PSReadlineOption).HistorySavePath 
      # To be safe, we recreate the file (empty). 
      $null = New-Item -Type File -Path (Get-PSReadlineOption).HistorySavePath
    }

    # Clear PowerShell's own history 
    Clear-History

    # Clear PSReadline's *session* history.
    # General caveat (doesn't apply here, because we're removing the saved-history file):
    #   * By default (-HistorySaveStyle SaveIncrementally), if you use
    #    [Microsoft.PowerShell.PSConsoleReadLine]::ClearHistory(), any sensitive
    #    commands *have already been saved to the history*, so they'll *reappear in the next session*. 
    #   * Placing `Set-PSReadlineOption -HistorySaveStyle SaveAtExit` in your profile 
    #     SHOULD help that, but as of PSReadline v1.2, this option is BROKEN (saves nothing). 
    [Microsoft.PowerShell.PSConsoleReadLine]::ClearHistory()

  } else { # Without PSReadline, we only have a *session* history.

    Clear-Host

    # Clear the doskey library's buffer, used pre-PSReadline. 
    # !! Unfortunately, this requires sending key combination Alt+F7.
    # Thanks, https://stackoverflow.com/a/13257933/45375
    $null = [system.reflection.assembly]::loadwithpartialname("System.Windows.Forms")
    [System.Windows.Forms.SendKeys]::Sendwait('%{F7 2}')

    # Clear PowerShell's own history 
    Clear-History

  }

}

To clear the on screen display history (F7) you have to press Alt + F7.

This history is managed by the console buffer, not by PowerShell that has its history clearable by the Clear-History cmdlet.

To script it, try:

[System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")
[System.Windows.Forms.SendKeys]::Sendwait('%{F7 2}')

Tags:

Powershell

History

Recent Posts