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Trace-Command

  • Reference
Module:
Microsoft.PowerShell.Utility

Configures and starts a trace of the specified expression or command.

Syntax

Trace-Command
     [-InputObject <PSObject>]
     [-Name] <String[]>
     [[-Option] <PSTraceSourceOptions>]
     [-Expression] <ScriptBlock>
     [-ListenerOption <TraceOptions>]
     [-FilePath <String>]
     [-Force]
     [-Debugger]
     [-PSHost]
     [<CommonParameters>]
Trace-Command
     [-InputObject <PSObject>]
     [-Name] <String[]>
     [[-Option] <PSTraceSourceOptions>]
     [-Command] <String>
     [-ArgumentList <Object[]>]
     [-ListenerOption <TraceOptions>]
     [-FilePath <String>]
     [-Force]
     [-Debugger]
     [-PSHost]
     [<CommonParameters>]

Description

The Trace-Command cmdlet configures and starts a trace of the specified expression or command. It works like Set-TraceSource, except that it applies only to the specified command.

Examples

Example 1: Trace metadata processing, parameter binding, and an expression

This example starts a trace of metadata processing, parameter binding, and cmdlet creation and destruction of the Get-Process Notepad expression.

Trace-Command -Name metadata,parameterbinding,cmdlet -Expression {Get-Process Notepad} -PSHost

It uses the Name parameter to specify the trace sources, the Expression parameter to specify the command, and the PSHost parameter to send the output to the console. Because it doesn't specify any tracing options or listener options, the command uses the defaults:

  • All for the tracing options
  • None for the listener options

Example 2: Trace the actions of ParameterBinding operations

This example traces the actions of the ParameterBinding operations of PowerShell while it processes a Get-Alias expression that takes input from the pipeline.

$A = "i*"
Trace-Command ParameterBinding {Get-Alias $Input} -PSHost -InputObject $A

In Trace-Command, the InputObject parameter passes an object to the expression that's being processed during the trace.

The first command stores the string i* in the $A variable. The second command uses the Trace-Command cmdlet with the ParameterBinding trace source. The PSHost parameter sends the output to the console.

The expression being processed is Get-Alias $Input, where the $Input variable is associated with the InputObject parameter. The InputObject parameter passes the variable $A to the expression. In effect, the command being processed during the trace is Get-Alias -InputObject $A" or "$A | Get-Alias.

Example 3: Trace ParameterBinding operations for native commands

PowerShell 7.3 added the ability to trace parameter binding for native commands. The following example shows how PowerShell parses the command-line arguments for the native command TestExe.

$a = 'a" "b'
Trace-Command -PSHOST -Name ParameterBinding { TestExe -echoargs $a 'c" "d' e" "f }

DEBUG: 2023-02-27 14:20:45.3975 ParameterBinding Information: 0 : BIND NAMED native application line args [C:\Public\Toolbox\TestExe\testexe.exe]
DEBUG: 2023-02-27 14:20:45.3978 ParameterBinding Information: 0 :     BIND cmd line arg [-echoargs] to position [0]
DEBUG: 2023-02-27 14:20:45.3979 ParameterBinding Information: 0 :     BIND cmd line arg [a" "b] to position [1]
DEBUG: 2023-02-27 14:20:45.3980 ParameterBinding Information: 0 :     BIND cmd line arg [c" "d] to position [2]
DEBUG: 2023-02-27 14:20:45.3982 ParameterBinding Information: 0 :     BIND cmd line arg [e f] to position [3]
DEBUG: 2023-02-27 14:20:47.6092 ParameterBinding Information: 0 : CALLING BeginProcessing

Parameters

-ArgumentList

Specifies the parameters and parameter values for the command being traced. The alias for ArgumentList is Args. This feature is useful for debugging dynamic parameters.

For more information about the behavior of ArgumentList, see about_Splatting.

Type:Object[]
Aliases:Args
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-Command

Specifies a command that's being processed during the trace.

When you use this parameter, PowerShell processes the command just as it would be processed in a pipeline. For example, command discovery isn't repeated for each incoming object.

Type:String
Position:1
Default value:None
Required:True
Accept pipeline input:False
Accept wildcard characters:False

-Debugger

Indicates that the cmdlet sends the trace output to the debugger. You can view the output in any user-mode or kernel mode debugger or in Visual Studio. This parameter also selects the default trace listener.

Type:SwitchParameter
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-Expression

Specifies the expression that's being processed during the trace. Enclose the expression in braces ({}).

Type:ScriptBlock
Position:1
Default value:None
Required:True
Accept pipeline input:False
Accept wildcard characters:False

-FilePath

Specifies a file that the cmdlet sends the trace output to. This parameter also selects the file trace listener.

Type:String
Aliases:PSPath, Path
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-Force

Forces the command to run without asking for user confirmation. Used with the FilePath parameter. Even using the Force parameter, the cmdlet can't override security restrictions.

Type:SwitchParameter
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-InputObject

Specifies input to the expression that's being processed during the trace. You can enter a variable that represents the input that the expression accepts, or pass an object through the pipeline.

Type:PSObject
Position:Named
Default value:None
Required:False
Accept pipeline input:True
Accept wildcard characters:False

-ListenerOption

Specifies optional data to the prefix of each trace message in the output. The acceptable values for this parameter are:

  • None
  • LogicalOperationStack
  • DateTime
  • Timestamp
  • ProcessId
  • ThreadId
  • Callstack

None is the default.

These values are defined as a flag-based enumeration. You can combine multiple values together to set multiple flags using this parameter. The values can be passed to the ListenerOption parameter as an array of values or as a comma-separated string of those values. The cmdlet will combine the values using a binary-OR operation. Passing values as an array is the simplest option and also allows you to use tab-completion on the values.

Type:TraceOptions
Accepted values:None, LogicalOperationStack, DateTime, Timestamp, ProcessId, ThreadId, Callstack
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-Name

Specifies an array of PowerShell components that are traced. Enter the name of the trace source of each component. Wildcards are permitted. To find the trace sources on your computer, type Get-TraceSource.

Type:String[]
Position:0
Default value:None
Required:True
Accept pipeline input:False
Accept wildcard characters:False

-Option

Determines the type of events that are traced. The acceptable values for this parameter are:

  • None
  • Constructor
  • Dispose
  • Finalizer
  • Method
  • Property
  • Delegates
  • Events
  • Exception
  • Lock
  • Error
  • Errors
  • Warning
  • Verbose
  • WriteLine
  • Data
  • Scope
  • ExecutionFlow
  • Assert
  • All

All is the default.

The following values are combinations of other values:

  • ExecutionFlow: Constructor, Dispose, Finalizer, Method, Delegates, Events, Scope
  • Data: Constructor, Dispose, Finalizer, Property, Verbose, WriteLine
  • Errors: Error, Exception

These values are defined as a flag-based enumeration. You can combine multiple values together to set multiple flags using this parameter. The values can be passed to the Option parameter as an array of values or as a comma-separated string of those values. The cmdlet will combine the values using a binary-OR operation. Passing values as an array is the simplest option and also allows you to use tab-completion on the values.

Type:PSTraceSourceOptions
Accepted values:None, Constructor, Dispose, Finalizer, Method, Property, Delegates, Events, Exception, Lock, Error, Errors, Warning, Verbose, WriteLine, Data, Scope, ExecutionFlow, Assert, All
Position:2
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-PSHost

Indicates that the cmdlet sends the trace output to the PowerShell host. This parameter also selects the PSHost trace listener.

Type:SwitchParameter
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

Inputs

PSObject

You can pipe objects that represent input to the expression to this cmdlet.

Outputs

PSObject

This cmdlet returns no output of its own. The traced command may return output. This cmdlet writes the command trace to the debug stream.

Notes

Tracing is a method that developers use to debug and refine programs. When tracing, the program generates detailed messages about each step in its internal processing. The PowerShell tracing cmdlets are designed to help PowerShell developers, but they're available to all users. They let you monitor nearly every aspect of the functionality of the shell.

A trace source is the part of each PowerShell component that manages tracing and generates trace messages for the component. To trace a component, you identify its trace source.

Use Get-TraceSource to see a list of PowerShell components that are enabled for tracing.

A trace listener receives the output of the trace and displays it to the user. You can elect to send the trace data to a user-mode or kernel-mode debugger, to the host or console, to a file, or to a custom listener derived from the System.Diagnostics.TraceListener class.