PowerShell Scripts

Parameters

Parameters allow to pass values to the script.

Unnamed

set-strictMode -version latest

$first_argument  = $args[0]
$second_argument = $args[1]
…

Named arguments

param (
  $username,
  $password
)

set-strictMode -version latest

…

Using named arguments has the benefit that the script user can invoke the script with explicitly named argument names:

.\the-script.ps1 -username rene -password theMostSecretSecret

Note: the set-strictMode must follow the param statement, otherwise, PowerShell will complain with the error message param : The term 'param' is not recognized as the name of a cmdlet, function, script file, or operable program.….

Statements and keywords at the top of a script

If a script contains using statements, they need to be at the beginning of the script.

If the script also contains a param keyword (that defines the script's parameters), it must be after the using statements (if any) and before the rest of the script.

Only after the using and param statements/keywords can the script have a set-strictMode cmdLet.

Abort a script when it encounters an unrecognized term

The following script contains a typo: elsif instead of elseif.

$errorActionPreference = 'stop'
set-strictMode -version latest

$v = 5

foreach ($i in 0 .. 10) {

   if ( $v -gt $i ) {
      write-host 'v > i'
   }
   elsif ($i -lt 7) {
      write-host 'i < 7'
   }

}

Github repository about-PowerShell, path: /script/abort-on-unrecognized-term.ps1

When the interpreter encounters the corresponding line, it does not recognize elsif and consequently emits the error message The term 'elsif' is not recognized as a name of a cmdlet, function, script file, or executable program …

This error is considered non-terminating. Therefore, without setting the preference variable $errorActionPreference to stop, the script continues with its execution which causes this message to be printed ten times.

In order to abort a script when it encounters an unrecognized term, $errorActionPreference must be set to stop.

Determining script-name and script-path (within a script)

The file- name and location (directory) of a script can be determined within the script with the following automatic variables:

`$myInvocation.myCommand.name`	The script's file name
`$psScriptRoot`	The directory (without script's file name) where script is located
`$psCommandPath`	The complete path of the script (= directory + file name)
`$myInvocation.myCommand.path`	Alternative to get complete path

set-strictMode -version latest

write-host
write-host "  The name of script's file is            : $($myInvocation.myCommand.name)"
write-host "  It is located in the directory          : $psScriptRoot"
write-host
write-host "  Thus, the complete path to the script is: $psCommandPath"
write-host
write-host "  The directory can also be evaluated with"
write-host "  `$myInvocation.myCommand.path            : $($myInvocation.myCommand.path)"
write-host

Github repository about-PowerShell, path: /script/name-and-path.ps1

See also determining script name and directory using $myInvocation.