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Switch or Parameter

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I told my students that processing parameters in pairs, like a prior post demonstrated for another student, was a bad idea. That’s true because any list of parameters may contain switches and parameter/argument pairs.

A switch is a signal to turn on or off some behavior, like -v typically makes a utility produce a verbose (or wordy) display to console. Parameter and argument pairs are like name and value pairs in dictionaries. For example, you may have the following:

-o output.csv -s query.sql

The dash (–) identifies the parameter and the lack of one identifies an argument or value. So, here’s simply the PowerShell block re-written to demonstrate how to handled an argument list that may contain switches and parameter/argument pairs:

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# Wrap the Parameter call to avoid a type casting warning.
try {
  param (
    [Parameter(Mandatory)][hashtable]$args
  )
}
catch {}
 
# Check for switches and parameters with arguments.
for ($i = 0; $i -lt $args.count; $i += 1) {
  if (($args[$i].startswith("-")) -and ($args[$i + 1].startswith("-"))) {
    $verbose = $true
	# Print to verbose console.
    if ($verbose) { Get-Message $args[$i] }}
  elseif ($args[$i].startswith("-")) {
    # Print to verbose console.
    if ($verbose) { Get-Message $args[$i] $args[$i + 1] }
 
    # Evaluate and take action on parameters and values.
    if ($args[$i] -eq "-o") {
      $outfile = $args[$i + 1] }
    elseif ($args[$i] -eq "-q") {
      $sqlFile = $args[$i + 1] }
    elseif ($args[$i] -eq "-s") {
      # You must evaluate the argument before using it to access an enum
      # value; and the program assumes an incorrect SQL statement value
      #	means you should assume the SQL statemente is a query.
      if ([SQLStatements]::($args[$i + 1])) {
        $stmt = [SQLStatements]::($args[$i + 1]) }}	
    elseif ($args[$i] -eq "-p") {
      $path = $args[$i + 1] }
  }
}

I hope this helps those looking for a solution to processing a parameter list in a PowerShell script.

Written by maclochlainn

April 21st, 2022 at 5:15 pm

Posted in Microsoft Windows 10,Microsoft Windows 11,PowerShell,Windows 10,Windows OS

Tagged with , ,