python Resource

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Use the python resource to execute scripts using the Python interpreter. This resource may also use any of the actions and properties that are available to the execute resource. 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

The python resource has the following syntax:

python 'hello world' do
  code <<-EOH
    print "Hello world! From Chef and Python."
  EOH
end

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

python 'name' do
  code             String
  command          String, Array # default value: 'name' unless specified
  creates          String
  cwd              String
  default_env      true, false # default value: false
  domain           String
  elevated         true, false # default value: false
  environment      Hash
  flags            String
  group            String, Integer
  input            String
  interpreter      String
  live_stream      true, false # default value: false
  login            true, false # default value: false
  password         String
  returns          Integer, Array # default value: 0
  timeout          Integer, String, Float # default value: 3600
  user             String, Integer
  action           Symbol # defaults to :run if not specified
end

where:

• python is the resource.
• name is the name given to the resource block.
• action identifies which steps Chef Infra Client will take to bring the node into the desired state.
• code, command, creates, cwd, default_env, domain, elevated, environment, flags, group, input, interpreter, live_stream, login, password, returns, timeout, and user are the properties available to this resource.

Actions

The python resource has the following actions:

:nothing

This resource block doesn’t act unless notified by another resource to take action. Once notified, this resource block either runs immediately or is queued up to run at the end of a Chef Infra Client run.

:run

Run a command. (default)

Properties

The python resource has the following properties:

code

Ruby Type: String | REQUIRED

A quoted string of code to be executed.

creates

Ruby Type: String

Prevent a command from creating a file when that file already exists.

cwd

Ruby Type: String

The current working directory from which the command will be run.

environment

Ruby Type: Hash

A Hash of environment variables in the form of ({'ENV_VARIABLE' => 'VALUE'}). Note: These variables must exist for a command to be run successfully.

flags

Ruby Type: String

One or more command line flags that are passed to the interpreter when a command is invoked.

group

Ruby Type: String, Integer

The group name or group ID that must be changed before running a command.

ignore_failure

Ruby Type: true, false | Default Value: false

Continue running a recipe if a resource fails for any reason.

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 notify more than one resource; use a notifies statement for each resource to be notified.

If the referenced resource doesn’t exist, an error is raised. In contrast, subscribes won’t fail if the source resource isn’t found.

A timer specifies the point during a Chef Infra Client run at which a notification is run. The following timers are available:

:before

Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.

:delayed

Default. Specifies that a notification should be queued up, and then executed at the end of a Chef Infra Client run.

:immediate, :immediately

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

The syntax for notifies is:

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

returns

Ruby Type: Integer, Array | Default Value: 0

The return value for a command. This may be an array of accepted values. An exception is raised when the return value(s) do not match.

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.

Note that subscribes doesn’t apply the specified action to the resource that it listens to - for example:

file '/etc/nginx/ssl/example.crt' do
  mode '0600'
  owner 'root'
end

service 'nginx' do
  subscribes :reload, 'file[/etc/nginx/ssl/example.crt]', :immediately
end

In this case the subscribes property reloads the nginx service whenever its certificate file, located under /etc/nginx/ssl/example.crt, is updated. subscribes doesn’t make any changes to the certificate file itself, it merely listens for a change to the file, and executes the :reload action for its resource (in this example nginx) when a change is detected.

If the other resource doesn’t exist, the subscription won’t raise an error. Contrast this with the stricter semantics of notifies, which will raise an error if the other resource doesn’t exist.

A timer specifies the point during a Chef Infra Client run at which a notification is run. The following timers are available:

:before

Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.

:delayed

Default. Specifies that a notification should be queued up, and then executed at the end of a Chef Infra Client run.

:immediate, :immediately

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

The syntax for subscribes is:

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

timeout

Ruby Type: Integer, String, Float | Default Value: 3600

The amount of time (in seconds) a command is to wait before timing out.

umask

Ruby Type: String, Integer

The file mode creation mask, or umask.

user

Ruby Type: String, Integer

The user name of the user identity with which to launch the new process. The user name may optionally be specified with a domain, i.e. domain\user or user@my.dns.domain.com via Universal Principal Name (UPN)format. It can also be specified without a domain simply as user if the domain is instead specified using the domain property. On Windows only, if this property is specified, the password property must be specified.

Common Resource Functionality

Chef resources include common properties, notifications, and resource guards.

Guards

A guard property can be used to evaluate the state of a node during the execution phase of a Chef Infra Client run. Based on the results of this evaluation, a guard property is then used to tell Chef Infra 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 isn’t 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 isn’t 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’s being executed, and then if the desired state is present, for Chef Infra Client to don’thing.

The following properties can be used to define a guard that’s evaluated during the execution phase of a Chef Infra 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.

Examples

This resource does not have any examples.