powershell_script

Use the powershell_script resource to execute a script using the Windows PowerShell interpreter, much like how the script and script-based resources—bash, csh, perl, python, and ruby—are used. The powershell_script is specific to the Microsoft Windows platform and the Windows PowerShell interpreter.

The powershell_script resource creates and executes a temporary file (similar to how the script resource behaves), rather than running the command inline. Commands that are executed with this resource are (by their nature) not idempotent, as they are typically unique to the environment in which they are run. Use not_if and only_if to guard this resource for idempotence.

Syntax

A powershell_script resource block executes a batch script using the Windows PowerShell interpreter. For example, writing to an interpolated path:

powershell_script 'write-to-interpolated-path' do
  code <<-EOH
  $stream = [System.IO.StreamWriter] "#{Chef::Config[:file_cache_path]}/powershell-test.txt"
  $stream.WriteLine("In #{Chef::Config[:file_cache_path]}...word.")
  $stream.close()
  EOH
end

The full syntax for all of the properties that are available to the powershell_script resource is:

powershell_script 'name' do
  architecture               Symbol
  code                       String
  command                    String, Array
  convert_boolean_return     TrueClass, FalseClass
  flags                      String
  interpreter                String
  notifies                   # see description
  provider                   Chef::Provider::PowershellScript
  subscribes                 # see description
  action                     Symbol # defaults to :run if not specified
end

where

• powershell_script is the resource
• name is the name of the resource block
• command is the command to be run and cwd is the location from which the command is run
• :action identifies the steps the chef-client will take to bring the node into the desired state
• architecture, code, command, convert_boolean_return, flags, interpreter, and provider are properties of this resource, with the Ruby type shown. See “Properties” section below for more information about all of the properties that may be used with this resource.

Actions

This resource has the following actions:

:nothing

Inherited from execute resource. Prevent a command from running. This action is used to specify that a command is run only when another resource notifies it.

:run

Default. Run the script.

Properties

This resource has the following properties:

architecture

Ruby Type: Symbol

The architecture of the process under which a script is executed. If a value is not provided, the chef-client defaults to the correct value for the architecture, as determined by Ohai. An exception is raised when anything other than :i386 is specified for a 32-bit process. Possible values: :i386 (for 32-bit processes) and :x86_64 (for 64-bit processes).

code

Ruby Type: String

A quoted (” ”) string of code to be executed.

command

Ruby Types: String, Array

The name of the command to be executed. Default value: the name of the resource block See “Syntax” section above for more information.

convert_boolean_return

Ruby Types: TrueClass, FalseClass

Return 0 if the last line of a command is evaluated to be true or to return 1 if the last line is evaluated to be false. Default value: false.

When the guard_intrepreter common attribute is set to :powershell_script, a string command will be evaluated as if this value were set to true. This is because the behavior of this attribute is similar to the value of the "$?" expression common in UNIX interpreters. For example, this:

powershell_script 'make_safe_backup' do
  guard_interpreter :powershell_script
  code 'cp ~/data/nodes.json ~/data/nodes.bak'
  not_if 'test-path ~/data/nodes.bak'
end

is similar to:

bash 'make_safe_backup' do
  code 'cp ~/data/nodes.json ~/data/nodes.bak'
  not_if 'test -e ~/data/nodes.bak'
end

flags

Ruby Type: String

A string that is passed to the Windows PowerShell command. Default value: -NoLogo, -NonInteractive, -NoProfile, -ExecutionPolicy RemoteSigned, -InputFormat None, -File.

ignore_failure

Ruby Types: TrueClass, FalseClass

Continue running a recipe if a resource fails for any reason. Default value: false.

interpreter

Ruby Type: String

The script interpreter to use during code execution. Changing the default value of this property is not supported.

notifies

Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may notify another resource to take action when its state changes. Specify a 'resource[name]', the :action that resource should take, and then the :timer for that action. A resource may notifiy more than one resource; use a notifies statement for each resource to be notified.

A timer specifies the point during the chef-client run at which a notification is run. The following timers are available:

:delayed

Default. Specifies that a notification should be queued up, and then executed at the very end of the chef-client run.

:immediate, :immediately

Specifies that a notification should be run immediately, per resource notified.

The syntax for notifies is:

notifies :action, 'resource[name]', :timer

provider

Ruby Type: Chef Class

Optional. Explicitly specifies a provider.

retries

Ruby Type: Integer

The number of times to catch exceptions and retry the resource. Default value: 0.

retry_delay

Ruby Type: Integer

The retry delay (in seconds). Default value: 2.

subscribes

Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may listen to another resource, and then take action if the state of the resource being listened to changes. Specify a 'resource[name]', the :action to be taken, and then the :timer for that action.

A timer specifies the point during the chef-client run at which a notification is run. The following timers are available:

:delayed

Default. Specifies that a notification should be queued up, and then executed at the very end of the chef-client run.

:immediate, :immediately

Specifies that a notification should be run immediately, per resource notified.

The syntax for subscribes is:

subscribes :action, 'resource[name]', :timer

Guards

A guard property can be used to evaluate the state of a node during the execution phase of the chef-client run. Based on the results of this evaluation, a guard property is then used to tell the chef-client if it should continue executing a resource. A guard property accepts either a string value or a Ruby block value:

• A string is executed as a shell command. If the command returns 0, the guard is applied. If the command returns any other value, then the guard property is not applied. String guards in a powershell_script run Windows PowerShell commands and may return true in addition to 0.
• A block is executed as Ruby code that must return either true or false. If the block returns true, the guard property is applied. If the block returns false, the guard property is not applied.

A guard property is useful for ensuring that a resource is idempotent by allowing that resource to test for the desired state as it is being executed, and then if the desired state is present, for the chef-client to do nothing.

Attributes

The following properties can be used to define a guard that is evaluated during the execution phase of the chef-client run:

not_if

Prevent a resource from executing when the condition returns true.

only_if

Allow a resource to execute only if the condition returns true.

Arguments

The following arguments can be used with the not_if or only_if guard properties:

:user

Specify the user that a command will run as. For example:

not_if 'grep adam /etc/passwd', :user => 'adam'

:group

Specify the group that a command will run as. For example:

not_if 'grep adam /etc/passwd', :group => 'adam'

:environment

Specify a Hash of environment variables to be set. For example:

not_if 'grep adam /etc/passwd', :environment => {
  'HOME' => '/home/adam'
}

:cwd

Set the current working directory before running a command. For example:

not_if 'grep adam passwd', :cwd => '/etc'

:timeout

Set a timeout for a command. For example:

not_if 'sleep 10000', :timeout => 10

Providers

Where a resource represents a piece of the system (and its desired state), a provider defines the steps that are needed to bring that piece of the system from its current state into the desired state.

The chef-client will determine the correct provider based on configuration data collected by Ohai at the start of the chef-client run. This configuration data is then mapped to a platform and an associated list of providers.

Generally, it’s best to let the chef-client choose the provider, and this is (by far) the most common approach. However, in some cases, specifying a provider may be desirable. There are two approaches:

• Use a more specific short name—yum_package "foo" do instead of package "foo" do, script "foo" do instead of bash "foo" do, and so on—when available
• Use the provider property within the resource block to specify the long name of the provider as a property of a resource. For example: provider Chef::Provider::Long::Name

This resource has the following providers:

Chef::Provider::PowershellScript, powershell_script

The default provider for all platforms.

Examples

The following examples demonstrate various approaches for using resources in recipes. If you want to see examples of how Chef uses resources in recipes, take a closer look at the cookbooks that Chef authors and maintains: https://github.com/chef-cookbooks.

Write to an interpolated path

powershell_script 'write-to-interpolated-path' do
  code <<-EOH
  $stream = [System.IO.StreamWriter] "#{Chef::Config[:file_cache_path]}/powershell-test.txt"
  $stream.WriteLine("In #{Chef::Config[:file_cache_path]}...word.")
  $stream.close()
  EOH
end

Change the working directory

powershell_script 'cwd-then-write' do
  cwd Chef::Config[:file_cache_path]
  code <<-EOH
  $stream = [System.IO.StreamWriter] "C:/powershell-test2.txt"
  $pwd = pwd
  $stream.WriteLine("This is the contents of: $pwd")
  $dirs = dir
  foreach ($dir in $dirs) {
    $stream.WriteLine($dir.fullname)
  }
  $stream.close()
  EOH
end

Change the working directory in Microsoft Windows

powershell_script 'cwd-to-win-env-var' do
  cwd '%TEMP%'
  code <<-EOH
  $stream = [System.IO.StreamWriter] "./temp-write-from-chef.txt"
  $stream.WriteLine("chef on windows rox yo!")
  $stream.close()
  EOH
end

Pass an environment variable to a script

powershell_script 'read-env-var' do
  cwd Chef::Config[:file_cache_path]
  environment ({'foo' => 'BAZ'})
  code <<-EOH
  $stream = [System.IO.StreamWriter] "./test-read-env-var.txt"
  $stream.WriteLine("FOO is $env:foo")
  $stream.close()
  EOH
end

Evaluate for true and/or false

Use the convert_boolean_return attribute to raise an exception when certain conditions are met. For example, the following fragments will run successfully without error:

powershell_script 'false' do
  code '$false'
end

and:

powershell_script 'true' do
  code '$true'
end

whereas the following will raise an exception:

powershell_script 'false' do
  convert_boolean_return true
  code '$false'
end