TOPIC
    about_Language_Keywords

SHORT DESCRIPTION
    Describes the keywords in the Windows PowerShell scripting language.


LONG DESCRIPTION
    Windows PowerShell has the following language keywords. For more 
    information, see the about topic for the keyword and the information that 
    follows the table.


        Keyword            Reference
        -------            ---------
        Begin              about_Functions, about_Functions_Advanced
        Break              about_Break, about_Trap
        Catch              about_Try_Catch_Finally
        Continue           about_Continue, about_Trap
        Data               about_Data_Sections
        Do                 about_Do, about_While 
        Dynamicparam       about_Functions_Advanced_Parameters
        Else               about_If 
        Elseif             about_If 
        End                about_Functions, about_Functions_Advanced_Methods
        Exit               Described in this topic.
        Filter             about_Functions
        Finally            about_Try_Catch_Finally
        For                about_For
        Foreach            about_Foreach
        From               Reserved for future use.
        Function           about_Functions, about_Functions_Advanced
        If                 about_If
        In                 about_Foreach
        Param              about_Functions
        Process            about_Functions, about_Functions_Advanced
        Return             about_Return
        Switch             about_Switch
        Throw              about_Throw, about_Functions_Advanced_Methods
        Trap               about_Trap, about_Break, about_Try_Catch_Finally
        Try                about_Try_Catch_Finally
        Until              about_Do
        While              about_While, about_Do


  Language Keywords

      Begin 
      -----

      Specifies one part of the body of a function, along with the 
      Dynamicparam, Process, and End keywords. The Begin statement list runs 
      one time before any objects are received from the pipeline. 

      Syntax:

          function <name> { 
              dynamicparam {<statement list>}
              begin {<statement list>}
              process {<statement list>}
              end {<statement list>}
          }

      Break
      -----

      Causes a script to exit a loop. 

      Syntax:

          while (<condition>) {
              <statements>
                   ...
              break 
                   ...
              <statements> 
          }

      Catch
      -----

      Specifies a statement list to run if an error occurs in the 
      accompanying Try statement list. An error type requires brackets. The 
      second pair of brackets indicates that the error type is optional.

      Syntax:
      
          try {<statement list>}
          catch [[<error type>]] {<statement list>}

      Continue
      --------

      Causes a script to stop running a loop and to go back to the condition. 
      If the condition is met, the script begins the loop again.

      Syntax:

          while (<condition>) {
              <statements>
                  ...
              continue 
                  ...
              <statements> 
          }

      Data   
      ---- 

      In a script, defines a section that isolates data from the script logic. 
      Can also include If statements and some limited commands.

      Syntax:

      data <variable> [-supportedCommand <cmdlet-name>] {<permitted content>}

      Do   
      --

      Used with the While or Until keyword as a looping construct. Windows 
      PowerShell runs the statement list at least one time, unlike a loop that 
      uses While.

      Syntax:

          do {<statement list>} while (<condition>)

          do {<statement list>} until (<condition>)

      Dynamicparam
      ------------

      Specifies one part of the body of a function, along with the Begin, 
      Process, and End keywords. Dynamic parameters are added at run time.

      Syntax:

          function <name> { 
              dynamicparam {<statement list>}
              begin {<statement list>}
              process {<statement list>}
              end {<statement list>}
          }

      Else
      ----

      Used with the If keyword to specify the default statement list.

      Syntax:

          if (<condition>) {<statement list>}
          else {<statement list>}

      Elseif
      ------

      Used with the If and Else keywords to specify additional conditionals. 
      The Else keyword is optional.

      Syntax:

          if (<condition>) {<statement list>}
          elseif (<condition>) {<statement list>}
          else {<statement list>}

      End
      ---

      Specifies one part of the body of a function, along with the 
      Dynamicparam, Begin, and End keywords. The End statement list runs one 
      time after all the objects have been received from the pipeline.

      Syntax:

          function <name> { 
              dynamicparam {<statement list>}
              begin {<statement list>}
              process {<statement list>}
              end {<statement list>}
          }

      Exit
      ----

      Causes Windows PowerShell to exit a script or a Windows PowerShell 
      instance.

      Syntax:

          exit

      Filter 
      ------

      Specifies a function in which the statement list runs one time for each 
      input object. It has the same effect as a function that contains only a 
      Process block.

      Syntax:

          filter <name> {<statement list>}

      Finally
      -------

      Defines a statement list that runs after statements that are associated 
      with Try and Catch. A Finally statement list runs even if you press 
      CTRL+C to leave a script or if you use the Exit keyword in the script.

      Syntax:

          try {<statement list>}
          catch [<error type] {<statement list>}
          finally {<statement list>}

      For   
      ---

      Defines a loop by using a condition. 

      Syntax:

          for (<initialize>; <condition>; <iterate>) {<statement list>}

      Foreach
      -------
      
      Defines a loop by using each member of a collection.

      Syntax:

          foreach (<item> in <collection>){<statement list>}

      From
      -----

      Reserved for future use.

      Function
      --------

      Creates a named statement list of reusable code. You can name the scope a 
      function belongs to. And, you can specify one or more named parameters by 
      using the Param keyword. Within the function statement list, you can 
      include Dynamicparam, Begin, Process, and End statement lists.

      Syntax:

          function [<scope:>]<name> { 
              param ([type]<$pname1> [, [type]<$pname2>])
              dynamicparam {<statement list>}
              begin {<statement list>}
              process {<statement list>}
              end {<statement list>}
          }

      You also have the option of defining one or more parameters outside the 
      statement list after the function name.

      Syntax:

          function [<scope:>]<name> [([type]<$pname1>, [[type]<$pname2>])] { 
              dynamicparam {<statement list>}
              begin {<statement list>}
              process {<statement list>}
              end {<statement list>}
          }

      If
      --

      Defines a conditional.

      Syntax:

          if (<condition>) {<statement list>}

      In
      --

      Used in a Foreach statement to create a loop that uses each member of a 
      collection.

      Syntax:

          foreach (<item> in <collection>){<statement list>}

      Param
      -----

      Defines the parameters in a function.

      Syntax:

          function [<scope:>]<name> {
              param ([type]<$pname1>[, [[type]<$pname2>]])
              <statement list>
          }

      Process
      -------

      Specifies a part of the body of a function, along with the Dynamicparam, 
      Begin, and End keywords. When a Process statement list receives input 
      from the pipeline, the Process statement list runs one time for each 
      element from the pipeline. If the pipeline provides no objects, the 
      Process statement list does not run. If the command is the first command 
      in the pipeline, the Process statement list runs one time.

      Syntax:

          function <name> { 
              dynamicparam {<statement list>}
              begin {<statement list>}
              process {<statement list>}
              end {<statement list>}
          }


      Return 
      ------

      Causes Windows PowerShell to leave the current scope, such as a script or 
      function, and writes the optional expression to the output.

      Syntax:

          return [<expression>]

      Switch
      ------

      Specifies a variety of actions to be performed on items from the pipeline 
      or from a file. You can use either of the following syntax models.

      Syntax 1:

          switch [-regex|-wildcard|-exact][-casesensitive] ( pipeline )
    
          { 
              <string>|<number>|<variable>|{ <expression> } {<statement list>}
              <string>|<number>|<variable>|{ <expression> } {<statement list>}
                    ...
              default {<statement list>}
          }


      Syntax 2:

          switch [-regex|-wildcard|-exact][-casesensitive] -file filename
          { 
              <string>|<number>|<variable>|{ <expression> } {<statement list>}
              <string>|<number>|<variable>|{ <expression> } {<statement list>}
                    ...
              default {<statement list>}
          }


      Throw
      -----

      Throws an object as an error.

      Syntax:

          throw [<object>]

      Trap 
      ----

      Defines a statement list to be run if an error is encountered. An error 
      type requires brackets. The second pair of brackets indicates that the 
      error type is optional.

      Syntax:

          trap [[<error type>]] {<statement list>}

      Try
      ---

      Defines a statement list to be checked for errors while the statements 
      run. If an error occurs, Windows PowerShell continues running in a Catch 
      or Finally statement. An error type requires brackets. The second pair of 
      brackets indicates that the error type is optional.

      Syntax:

          try {<statement list>}
          catch [[<error type]] {<statement list>}
          finally {<statement list>}

      Until
      -----

      Used in a Do statement as a looping construct where the statement list is 
      executed at least one time.

      Syntax:

          do {<statement list>} until (<condition>)

      While
      -----

      Used in a Do statement as a looping construct where the statement list is 
      executed at least one time.

      Syntax:

          do {<statement list>} while (<condition>)

SEE ALSO
     about_escape_characters
     about_special_characters
     about_wildcards
