Ensuring Script Portability with #requires
With the MshSnapIn model in Beta 3, there is no gaurantee that a certain Cmdlet or Provider, apart from those in the default MshSnapIns, is available at any point. There could be a number of reasons. The MshSnapIn may not have been installed. The MshSnapIn could be removed with the remove-mshsnapin Cmdlet or not even added yet. This will cause scripts using the unavailable commands to fail or worse exhibit unpredictable behaviors. Along with the MshSnapIn model, we introduce two flavors of #requires that a script can use to express dependencies on MshSnapIns and Monad version. The former has the following syntax:
#requires -MshSnapIn SomeMshSnapIn [-version N[.n]] where the parts in square brackets are optional. #requires must be at the beginning of a line.
When only MshSnapIn is specified, the script will run if and only if the MshSnapIn SomeMshSnapIn is already added with the Add-MshSnapIn Cmdlet (or the RunspaceConfiguration.AddMshSnapIn API). Moreover, if the major version N is specified, the added MshSnapin’s major version must match N. Furthermore, if the minor version n is also specified, the added MshSnapin’s minor version must be equal to or higher than n. Failing any of the checks will cause the script not to run. A script can have multiple #requires -MshSnapIn directives. In this case, all MshSnapIn checks will need to pass for the script to run.
The latter’s syntax is as follows.
#requires -version N[.n] where the parts in square brackets are optional. #requires must be at the beginning of a line.
When only the major version N is specified, the current Monad shell’s version must match N. If the minor version is also n specified, the current Monad shell’s minor version must be equal to or higher than n. Failing any of the checks will cause the script not to run.
Finally, for the custom shell environment, the #requires -ShellId flavor is still available. A script can have any combinations of the three #requires flavors. #requires -version will check the Monad shell version for all combinations. As for the other two flavors, here is the behavior summary:
| If a script has | Monad Shell | Custom Shell |
| #requires -MshSnapIn and no #requires -ShellId | Check MshSnapIn | Script won’t run |
| #requires -ShellId and no #requires -MshSnapIn | Script won’t run | Check ShellId |
| #requires -ShellId and #requires -MshSnapIn | Check MshSnapIn | Check ShellId |
—
Kevin Loo [MSFT]
Monad Development
Microsoft Corporation
This posting is provided “AS IS” with no warranties, and confers no rights.
[Edit: Monad has now been renamed to Windows PowerShell. This script or discussion may require slight adjustments before it applies directly to newer builds.]
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