CODEWITHSUNDEEP
powershellsyntaxparameter-passingpromptnon-interactive
kranthi
kranthi

Reputation: 77

Preventing interactive prompts for parameter values in scripts

I have a script, pingtest.ps1, which makes the following call:

Start-abc -SourceIpaddress x.y.x.z -Protocol TCP -DestinationIpAddress a.c.d.e

During execution it prompts for the source port and destination port.

How do I avoid these interactive prompts and instead pass the values in the same script?

Upvotes: 0

Views: 1622

Answers (1)

mklement0
mklement0

Reputation: 437111

tl;dr

Adding something like -SourcePort 42 and -DestinationPort 666 to your Start-abc call should prevent these interactive prompts (of course you must supply appropriate values in lieu of the sample values 42 and 666 used here).

To determine the exact name of these parameters and for background information, read on.

If invocation of a command doesn't supply arguments to all of its mandatory parameters (parameters that require values in order for the command to operate):

  • PowerShell by design interactively prompts for these arguments,
  • and only if you supply all required arguments (using valid values) does the command actually execute.

Note: This prompting mechanism is rarely used in practice and doesn't work with all parameter types - see GitHub issue #4068.

If you simply want to prevent interactive prompts at runtime, run your command via a new PowerShell instance started with -noninteractive:

powershell.exe -noninteractive -file C:\path\to\pingtest.ps1

This way your script won't prompt and report an error instead, which indicates the name of the (first) mandatory parameter for which no argument was provided.

Caveat: With default error handling in effect, script execution will still continue; setting $ErrorActionPreference = 'Stop' would prevent that.

If you want to determine at design time which parameters are mandatory, use
Get-Command <command> -Syntax.

If necessary and available, supplement with Get-Help -Detailed <command> (or -Full) or Get-Help -Parameter <parameterName> <command> to learn specifics about the parameters.
Note, however, that custom scripts and functions may not have help information associated with them.

PowerShell's syntax diagrams, documented in the conceptual about_Command_Syntax help topic, aren't the easiest to decipher, but they do tell you which parameters are mandatory.

Using the Get-Item cmdlet as an example:

PS> Get-Command Get-Item -Syntax

Get-Item [-Path] <string[]> [-Filter <string>] [-Include <string[]>] [-Exclude <string[]>] [-Force] [-Credential <pscredential>] [-UseTransaction] [-Stream <string[]>] [<CommonParameters>]

Get-Item -LiteralPath <string[]> [-Filter <string>] [-Include <string[]>] [-Exclude <string[]>] [-Force] [-Credential <pscredential>] [-UseTransaction] [-Stream <string[]>] [<CommonParameters>]

  • Each output line represents a distinct parameter set.

  • What parameters distinguish one parameters set from another isn't readily obvious; in this case, it is -Path vs. -LiteralPath, which is common for provider-related cmdlets.

  • In a given parameter set, any parameter that is not enclosed in [...] as a whole (around both the parameter name (e.g., -LiteralPath) and the parameter type (e.g., <string[]>)) is mandatory.

    • If only the parameter name is enclosed in [...] (e.g., [-Path]), the parameter is also mandatory, but arguments may be specified positionally - that is, you may omit the parameter name and specify just the argument (the value to bind to the parameter); e.g., instead of
      Get-Item -Path foo.txt you may specify just
      Get-Item foo.txt.

Based on the above, armed with the information as to:

  • which parameter set you'll be using
  • what its mandatory parameters are

you can then call your command in a manner that provides arguments to all mandatory parameters and thereby avoids interactive prompts.

Upvotes: 2

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