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Adding Commands |
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=============== |
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|
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Kamaki commands are implemented as python classes, decorated with a special |
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decorator called *command*. This decorator is a method of *kamaki.cli* that |
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adds a new command in a *CommandTree* structure. A *CommandTree* (package |
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*kamaki.cli.commant_tree*) is a data structure used by kamaki to manage command |
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namespaces. |
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|
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For demonstration purposes, the following set of kamaki commands will be |
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implemented in this document:: |
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|
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mygrp1 list all //show a list |
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mygrp1 list details [--match=<>] //show list of details |
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mygrp2 list all [regular expression] [-l] //list all subjects |
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mygrp2 info <id> [name] //get information for subject with id |
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|
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There are two command groups to implement i.e., *mygrp1* and *mygrp2*, |
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containing two commands each (*list_all*, *list_details* and *list_all*, *info* |
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respectively). To avoid ambiguities, command names are prefixed with the |
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command group they belong to, e.g., *mygrp1_list_all* and *mygrp2_list_all*. |
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The underscore is used to separate command namespaces. |
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|
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The first command (*mygrp1_list_all*) has the simplest possible syntax: no |
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parameters, no runtime arguments. The second accepts an optional runtime argument with a value. The third features an optional parameter and an optional |
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runtime flag argument. The last is an example of a command with an obligatory |
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and an optional parameter. |
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|
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Examples of the expected behavior in one-command mode: |
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|
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.. code-block:: console |
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|
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$kamaki mygrp1 |
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mygrp1 description |
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|
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Options |
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- - - - |
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list |
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$ kamaki mygrp1 list |
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|
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Options |
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- - - - |
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all show a list |
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details show a list of details |
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$ kamaki mygrp1 list all |
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... (a mygrp1_list_all instance runs) ... |
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$ kamaki mygrp2 list all 'Z[.]' -l |
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... (a mygrp2_list_all instance runs) ... |
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$ |
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|
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The CommandTree structure |
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------------------------- |
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|
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CommandTree manages a command by its namespace. Each command is stored in |
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a tree path, where each node is a name. A leaf is the end term of a namespace and contains a pointer to the command class to be executed. |
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|
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Here is an example from the actual kamaki command structure, where the commands |
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*file upload*, *file list* and *file info* are represented as shown bellow:: |
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|
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- file |
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''''''''|- info |
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|- list |
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|- upload |
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|
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Now, let's load the showcase example on CommandTrees:: |
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|
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- mygrp1 |
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''''''''|- list |
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'''''''|- all |
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|- details |
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|
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- mygrp2 |
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''''''''|- list |
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'''''''|- all |
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|- info |
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|
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Each command group should be stored on a different CommandTree. |
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|
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For that reason, command specification modules should contain a list of CommandTree objects, named *_commands*. This mechanism allows any interface |
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application to load the list of commands from the *_commands* array. |
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|
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The first name of the command path and a description (name, description) are needed to initializeg a CommandTree: |
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|
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.. code-block:: python |
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|
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_mygrp1_commands = CommandTree('mygrp', 'mygrp1 description') |
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_mygrp2_commands = CommandTree('mygrp', 'mygrp2 description') |
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|
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_commands = [_mygrp1_commands, _mygrp2_commands] |
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|
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|
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The command decorator |
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--------------------- |
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|
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All commands are specified by subclasses of *kamaki.cli.commands._command_init* |
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These classes are called "command specifications". |
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|
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The *command* decorator mines all the information needed to build a namespace |
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from a command specification:: |
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|
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class code ---> command() --> updated CommandTree structure |
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|
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Kamaki interfaces make use of the CommandTree structure. Optimizations are |
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possible by using special parameters on the command decorator method. |
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|
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.. code-block:: python |
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|
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def command(cmd_tree, prefix='', descedants_depth=None): |
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"""Load a class as a command |
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|
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:param cmd_tree: is the CommandTree to be updated with a new command |
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|
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:param prefix: of the commands allowed to be inserted ('' for all) |
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|
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:param descedants_depth: is the depth of the tree descendants of the |
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prefix command. |
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""" |
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|
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Creating a new command specification set |
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---------------------------------------- |
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|
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A command specification developer should create a new module (python file) with |
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one command specification class per command. Each class should be decorated |
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with *command*. |
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|
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.. code-block:: python |
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|
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... |
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_commands = [_mygrp1_commands, _mygrp2_commands] |
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|
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@command(_mygrp1_commands) |
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class mygrp1_list_all(): |
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... |
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|
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... |
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|
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A list of CommandTree structures must exist in the module scope, with the name |
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*_commands*. Different CommandTree objects correspond to different command |
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groups. |
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|
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Set command description |
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----------------------- |
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|
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The description of each command is the first line of the class commend. The |
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following declaration of *mygrp2-info* command has a "*get information for |
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subject with id*" description. |
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|
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.. code-block:: python |
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|
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... |
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@command(_mygrp2_commands) |
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class mygrp2_info(): |
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"""get information for subject with id |
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Anything from this point and bellow constitutes the long description |
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Please, mind the indentation, pep8 is not forgiving. |
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""" |
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... |
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|
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Description placeholders |
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------------------------ |
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|
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There is possible to create an empty command, that can act as a description |
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placeholder. For example, the *mygrp1_list* namespace does not correspond to an |
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executable command, but it can have a helpful description. In that case, create |
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a command specification class with a command and no code: |
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|
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.. code-block:: python |
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|
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@command(_mygrp1_commands) |
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class mygrp1_list(): |
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"""List mygrp1 objects. |
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There are two versions: short and detailed |
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""" |
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|
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.. warning:: A command specification class with no description is invalid and |
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will cause an error. |
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|
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Declare run-time argument |
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------------------------- |
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|
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A special argument mechanism allows the definition of run-time arguments. This |
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mechanism is based on argparse and is designed to simplify argument definitions |
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when specifying commands. |
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|
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Some basic argument types are defined at the |
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`argument module <code.html#module-kamaki.cli.argument>`_, but it is not |
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a bad idea to extent these classes in order to achieve specialized type |
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checking and syntax control. Still, in most cases, the argument types of the |
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argument package are enough for most cases. |
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|
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To declare a run-time argument on a specific command, the specification class |
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should contain a dict called *arguments* , where Argument objects are stored. |
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Each argument object is a run-time argument. Syntax checking happens at client |
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level, while the type checking is implemented in the Argument code (e.g., |
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IntArgument checks if the value is an int). |
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|
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.. code-block:: python |
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|
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from kamaki.cli.argument import ValueArgument |
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... |
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|
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@command(_mygrp1_commands) |
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class mygrp1_list_details(): |
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"""list of details""" |
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|
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def __init__(self, global_args={}): |
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global_args['match'] = ValueArgument( |
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'Filter results to match string', |
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('-m', '--match')) |
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self.arguments = global_args |
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|
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or more usually and elegantly: |
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|
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.. code-block:: python |
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|
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from kamaki.cli.argument import ValueArgument |
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|
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@command(_mygrp1_commands) |
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class mygrp1_list_details(): |
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"""List of details""" |
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|
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arguments = dict( |
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match=ValueArgument( |
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'Filter output to match string', ('-m', --match')) |
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) |
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|
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Accessing run-time arguments |
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---------------------------- |
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|
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To access run-time arguments, users can use the *_command_init* interface, |
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which implements *__item__* accessors to handle run-time argument values. In |
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other words, one may get the value of an argument with *self[<argument>]*. |
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|
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.. code-block:: python |
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|
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from kamaki.cli.argument import ValueArgument |
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from kamaki.cli.commands import _command_init |
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|
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@command(_mygrp1_commands) |
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class mygrp1_list_details(_command_init): |
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"""List of details""" |
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|
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arguments = dict( |
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match=ValueArgument( |
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'Filter output to match string', ('-m', --match')) |
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) |
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|
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def check_runtime_arguments(self): |
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... |
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assert self['match'] == self.arguments['match'].value |
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... |
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|
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The main method and command parameters |
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-------------------------------------- |
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|
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The command behavior for each command class is coded in *main*. The |
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parameters of *main* method affect the syntax of the command. In specific:: |
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|
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main(self, param) - obligatory parameter <param> |
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main(self, param=None) - optional parameter [param] |
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main(self, param1, param2=42) - <param1> [param2] |
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main(self, param1____param2) - <param1:param2> |
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main(self, param1____param2=[]) - [param1:param2] |
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main(self, param1____param2__) - <param1[:param2]> |
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main(self, param1____param2__='') - [param1[:param2]] |
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main(self, *args) - arbitary number of params [...] |
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main(self, param1____param2, *args) - <param1:param2> [...] |
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|
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Let's have a look at the command specification class again, and highlight the |
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parts that affect the command syntax: |
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|
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.. code-block:: python |
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:linenos: |
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|
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from kamaki.cli.argument import FlagArgument |
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... |
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|
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_commands = [_mygrp1_commands, _mygrp2_commands] |
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... |
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|
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@command(_mygrp2_commands) |
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class mygrp2_list_all(): |
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"""List all subjects |
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Refers to the subject accessible by current user |
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""" |
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|
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arguments = dict(FlagArgument('detailed list', '-l')) |
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|
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def main(self, reg_exp=None): |
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... |
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|
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The above lines contain the following information: |
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|
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* Namespace and name (line 8): mygrp2 list all |
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* Short (line 9) and long (line 10) description |
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* Parameters (line 15): [reg exp] |
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* Runtime arguments (line 13): [-l] |
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* Runtime arguments help (line 13): detailed list |
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|
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.. tip:: It is suggested to code the main functionality in a member method |
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called *_run*. This allows the separation between syntax and logic. For |
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example, an external library may need to call a command without caring |
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about its command line behavior. |
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|
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Letting kamaki know |
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------------------- |
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|
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Kamaki will load a command specification *only* if it is set as a configurable |
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option. To demonstrate this, let the command specifications coded above be |
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stored in a file named *grps.py*. |
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|
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The developer should move the file *grps.py* to *kamaki/cli/commands*, the |
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default place for command specifications |
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|
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These lines should be contained in the kamaki configuration file for a new |
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command specification module to work: |
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:: |
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|
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[global] |
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mygrp1_cli = grps |
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mygrp2_cli = grps |
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|
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or equivalently: |
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|
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.. code-block:: console |
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|
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$ kamaki config set mygrp1_cli grps |
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$ kamaki config set mygrp2_cli grps |
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|
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.. note:: running a command specification from a different path is supported. |
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To achieve this, add a *<group>_cli = </path/to/module>* line in the |
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configure file under the *global* section |
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|
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An example:: |
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|
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[global] |
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mygrp_cli = /another/path/grps.py |
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|
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Summary: create a command set |
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----------------------------- |
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|
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.. code-block:: python |
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|
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# File: grps.py |
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|
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from kamaki.cli.commands import _command_init |
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from kamaki.cli.command_tree import CommandTree |
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from kamaki.cli.argument import ValueArgument, FlagArgument |
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... |
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|
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|
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# Initiallize command trees |
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|
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_mygrp1_commands = CommandTree('mygrp', 'mygrp1 description') |
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_mygrp2_commands = CommandTree('mygrp', 'mygrp2 description') |
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|
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_commands = [_mygrp1_commands, _mygrp2_commands] |
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|
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|
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# Define command specifications |
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|
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|
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@command(_mygrp1_commands) |
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class mygrp1_list(_command_init): |
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"""List mygrp1 objects. |
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There are two versions: short and detailed |
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""" |
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|
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|
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@command(_mygrp1_commands) |
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class mygrp1_list_all(_command_init): |
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"""show a list""" |
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|
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def _run(): |
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... |
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|
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def main(self): |
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self._run() |
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|
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|
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@command(_mygrp1_commands) |
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class mygrp1_list_details(_command_init): |
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"""show list of details""" |
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|
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arguments = dict( |
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match=ValueArgument( |
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'Filter output to match string', ('-m', --match')) |
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) |
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|
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def _run(self): |
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match_value = self['match'] |
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... |
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|
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def main(self): |
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self._run() |
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|
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|
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#The following will also create a mygrp2_list command with no description |
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|
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|
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@command(_mygrp2_commands) |
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class mygrp2_list_all(_command_init): |
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"""list all subjects""" |
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|
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arguments = dict( |
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list=FlagArgument('detailed listing', '-l') |
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) |
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|
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def _run(self, regexp): |
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... |
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if self['list']: |
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... |
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else: |
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... |
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|
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def main(self, regular_expression=None): |
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self._run(regular_expression) |
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|
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|
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@command(_mygrp2_commands) |
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class mygrp2_info(_command_init): |
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"""get information for subject with id""" |
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|
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def _run(self, grp_id, grp_name): |
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... |
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|
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def main(self, id, name=''): |
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self._run(id, name) |