Hacking PowerShell command history

HackingCommandHistory.ps1

# IMPORTANT NOTE: This hack has evolved, and HistoryPx is now a full PowerShell module
# that is hosted on GitHub and can be found here: github.com/KirkMunro/HistoryPx

# First set up some interesting hacks
New-Module -Name HistoryPx -ScriptBlock {
    $PSModule = $ExecutionContext.SessionState.Module
    $global:__ = $null
    $global:MaximumDetailedHistoryCount = 50
    $global:PSDefaultParameterValues['Out-Default:OutVariable'] = 'global:__'
    $commandHistory = [ordered]@{}
    $previousOutput = $null
    $onCommandInvokeBreakpoint = Set-PSBreakpoint -Variable __ -Mode Write -Action {
        # When inside a variable breakpoint action, access the variable directly to get the old value,
        # and use Get-Variable -Name $_.Variable -ValueOnly to get the new value
        $success = $? -eq $true
        $variableValue = (Get-Variable -Name $_.Variable -Scope Global -ValueOnly).Clone()
        if ($variableValue -ne $null) {
            $output = $variableValue
            $previousHistoryInfo,$historyInfo = Get-History -Count 2
            if ($script:previousOutput -eq $output) {
                $output = $null
            } else {
                $sortA = @($script:previousOutput | Sort-Object)
                $sortB = @($output | Sort-Object)
                if ($sortA.Count -eq $sortB.Count) {
                    $equivalent = $true
                    for ($index = 0; $index -lt $sortA.Count; $index++) {
                        if ($sortA[$index] -ne $sortB[$index]) {
                            $equivalent = $false
                            break
                        }
                    }
                    if ($equivalent) {
                        $output = $null
                    } else {
                        $script:previousOutput = $output
                    }
                } else {
                    $script:previousOutput = $output
                }
            }
            $script:commandHistory.Add($historyInfo.Id.ToString(),[pscustomobject]@{
                     PSTypeName = 'DetailedHistoryInfo'
                             Id = $historyInfo.Id
                    CommandLine = $historyInfo.CommandLine
                       Duration = $(if ($historyInfo.ExecutionStatus -eq [System.Management.Automation.Runspaces.PipelineState]::Completed) {$historyInfo.EndExecutionTime - $historyInfo.StartExecutionTime})
                ExecutionStatus = $historyInfo.ExecutionStatus
                        Success = $success
                         Errors = @($global:Error.where{$_.InvocationInfo.HistoryId -eq $historyInfo.Id})
                         Output = $(if ($output -ne $null) {$output | Where-Object {$_.PSTypeNames -notcontains 'DetailedHistoryInfo'}})
            })
            while ($script:commandHistory.Count -gt $global:MaximumDetailedHistoryCount) {
                $script:commandHistory.RemoveAt(0)
            }
        }
    }

    Update-TypeData -TypeName DetailedHistoryInfo -DefaultDisplayPropertySet Id,CommandLine,Duration,Success

    function Get-HistoryDetail {
        [CmdletBinding()]
        [OutputType('DetailedHistoryInfo')]
        param()
        foreach ($key in $commandHistory.Keys) {
            $commandHistory[$key]
        }
    }

    $PSModule.OnRemove = {
        Remove-PSBreakpoint -Breakpoint $onCommandInvokeBreakpoint
        $global:PSDefaultParameterValues.Remove('Out-Default:OutVariable')
        Remove-Variable -Scope Global -Name MaximumDetailedHistoryCount
        Remove-Variable -Scope Global -Name __
    }
} | Import-Module

# Now generate some command history
1
2
'Fish'
gsv blah
3 > $null
gps -id $pid
get-eventlog -foo bar
[void]3
4
$true

# And show the detailed history output. Intriguing, no? :)
Get-HistoryDetail | ft Id,CommandLine,Success,Output,Errors