How to use c# switch parameters in powershell functions?

Question

I have a function

getinfo([string]$subcommand, [string]$argument)

What I would like to do is allow the argument to be of value '-h' or '-help' such that

getinfo hosts -h

would give a help text for the subcommand 'hosts'. Unfortunately, when i specify -h I think it doesn't assign the value of "-h" to $argument and instead creates a new argument.

I was thinking of using a switch parameter but I'm not sure if I can use that in a function in conjunction with $argument above.

Is this possible?

What do you mean "C# switch parameters"?

John Saunders
– John Saunders

2014-11-25 23:08:21 +00:00
Commented Nov 25, 2014 at 23:08 — John Saunders
– John Saunders, Commented Nov 25, 2014 at 23:08

Keith Hill · Accepted Answer · 2014-11-25 23:05:45Z

5

Stepping back a bit, you are trying to force a command paradigm on PowerShell that is not what I'd call idiomatic PowerShell. Why not create several functions each with their own help e.g. Get-HostInfo, Get-FooInfo, etc. Then you can use PowerShell's built-in documentation support e.g.:

<#
.SYNOPSIS
   Short description
.DESCRIPTION
   Long description
.PARAMETER Host
    Name of the host.
.EXAMPLE
   Example of how to use this cmdlet
.EXAMPLE
   Another example of how to use this cmdlet
#>
function Get-HostInfo($host) { ... }

This supports help in all the ways PowerShell users expect:

man Get-HostInfo
man Get-HostInfo -Example
man Get-HostInfo -Parameter Host
Get-HostInfo -?

answered Nov 25, 2014 at 23:05

Keith Hill

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1 Comment

kevmar Over a year ago

The built-in documentation is the way to go for defining help information. You want to be able to type Get-Help and the command should produce the needed help text. Writing your own code to do this breaks that idea. Let PowerShell do what it is good at.

Ansgar Wiechers · Accepted Answer · 2014-11-25 22:39:10Z

0

I'd do it like this:

getinfo([string]$subcommand, [switch][alias("h")]$Help) {
  switch ($subcommand) {
    'hosts' {
       if ($Help) { 'Usage: getinfo hosts ...'; return }
       ...
    }
    ...
  }
}

All arguments not matching a parameter are automatically stored in the variable $args, so you don't really need a parameter $argument. It has the advantage (or disadvantage, depending on your point of view), that it accepts even arguments that PowerShell would interpret as parameters. Example:

PS C:\> function getinfo($subcommand, [switch]$Help, $argument) {
>>   if ($Help) { 'help' }
>>   $argument
>> }
>>
PS C:\> getinfo 'a' 'b'
b
PS C:\> getinfo 'a' -x
PS C:\> getinfo 'a' 'b' -h
help
b
PS C:\> getinfo 'a' -x -h
help
PS C:\> function getinfo($subcommand, [switch]$Help) {
>>   if ($Help) { 'help' }
>>   $args[0]
>> }
>>
PS C:\> getinfo 'a' 'b'
b
PS C:\> getinfo 'a' -x
-x
PS C:\> getinfo 'a' 'b' -h
help
b
PS C:\> getinfo 'a' -x -h
help
-x

answered Nov 25, 2014 at 22:39

Ansgar Wiechers

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1 Comment

anoopb Over a year ago

That worked great. Thanks so much. I've got info([string]$subcommand, [string]$argument, [string]$filter, [switch][alias("h")]$help). Worked perfectly because as long as -h is set, i'm in business. Thanks again.

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