group: Address a set of resources¶

This command allows the experimenter to address a specific group of resources, in order to configure them or send them some given sub-commands.

Syntax¶

group(groupSelector).subcommand(param1, param2,...)

group(groupSelector).resource_path = value

group(groupSelector).resource_path(param1, param2,...)

where:

• groupSelector: The name of group of resources to address. Please refer to the description of the defGroup command for a list of valid syntax for groupSelector.

• subcommand: The sub-command to send to all the resources within this specific group.

• resource_path: A valid Resource Path to access/configure a given parameter of the resources within this specific group. Please refer to the Resource Path section of the OEDL Reference page for a list of valid Resource Paths.

sendMessage(name, arg1, arg2, ...)

name               - the name of the application to send the message to 
arg1, arg2, etc... - the list of arguments to send to the standard-in of the application

Note: the argX will be concatenated in a single text message separated by a blank space.
Thus if arg1="Hello" and arg2="There", the application will receive "Hello There" on its STDIN.
This is also equivalent to using only arg1="Hello There" 
A newline (\n) is added at the end of the string.

Usage Examples¶

Example 1¶

Usage of 'group' with a Resource Path to set the ESSIDs and channels of the resource within some specific groups. The resources here are wifi-enabled nodes.

Please refer to the Resource Path section of the OEDL Reference page for a list of valid Resource Paths

 1 # Defines 2 groups of nodes: 'one_wifi_node' and 'two_wifi_nodes'
 2 #
 3 defGroup('one_wifi_node', [1,1])
 4 defGroup('two_wifi_nodes', [[1,2],[1,3]])
 5 
 6 # Use 'group' to set the ESSIDs for the 1st wifi interface w0
 7 #
 8 # 1 - Set ESSID of the single node in 'one_wifi_node'
 9 # 2 - Set ESSID of the two nodes in 'two_wifi_nodes'
10 #
11 group('one_wifi_node').net.w0.essid = "network_alpha" 
12 group('two_wifi_nodes').net.w0.essid = "network_beta" 
13 
14 # Now do the same to set the channels...
15 #
16 group('one_wifi_node').net.w0.channel = '6'
17 group('two_wifi_nodes').net.w0.channel = '11'
18 
19 #
20 # Another way to do the above operation in one go...
21 #
22 group('one_wifi_node').net.w0 { |w|
23   w.essid = "network_alpha" 
24   w.channel = '6'
25 }
26 
27 group('two_wifi_nodes').net.w0 { |w|
28   w.essid = "network_beta" 
29   w.channel = '11'
30 }

Example 2¶

Usage of 'group' with a sub-command to start, stop, and send message to an application associated with the resource within some specific groups. The resources here are PC-based nodes.

Please refer to the description of the defGroup command for more detailed information of the 'defGroup' syntax.

 1 # Defines a group of nodes: 'two_nodes'
 2 # and associate the application "videogen" to the nodes in this group
 3 # (videogen is a fictif application, which generate video packets)
 4 #
 5 defGroup('two_nodes', [[1,1],[1,2]]) { |n|
 6   n.prototype('videogen')
 7 }
 8 
 9 # Use 'group' to start the applications on the nodes 
10 #
11 group('two_nodes').startApplications
12 
13 # Now use 'group' to send a message to the applications on the nodes 
14 # The application will receive this message on its standard-in input
15 #
16 group('two_nodes').sendMessage('videogen', 'increase pkt rate to 1024')
17 
18 # Note: the following line also does the exact same thing...
19 #
20 group('two_nodes').sendMessage('videogen', 'increase', 'pkt', 'rate', 'to', '1024')
21 
22 # Finally, use 'group' to stop the applications on the nodes 
23 #
24 group('two_nodes').stopApplications