1# Common Event Manager
2
3The Common Event Manager enables you to print common event information and publish common events. It provides the common event debugging and testing capabilities, for example, printing all public event subscribers, sent public events, and recipients, and simulating public event release.
4
5> **NOTE**
6>
7> Before using this tool, you must obtain the <!--Del-->[<!--DelEnd-->hdc tool<!--Del-->](../../device-dev/subsystems/subsys-toolchain-hdc-guide.md)<!--DelEnd--> and run the hdc shell command.
8
9## Commands
10
11### help
12
13* Function
14
15  Prints help information.
16
17* Method
18
19  ```
20  cem help
21  ```
22
23### publish
24
25* Function
26
27  Publishes a common event.
28
29* Method
30
31  ```
32  cem publish [<options>]
33  ```
34
35  The table below describes the available options.
36
37  | Name        | Description                                  |
38  | ------------ | ------------------------------------------ |
39  | -e/--event   | Name of the common event to publish. Mandatory.                    |
40  | -o/--ordered | Indicates that the common event to publish is ordered. Optional. By default, non-ordered events are published.  |
41  | -c/--code    | Result code of the common event. Optional.                  |
42  | -d/--data    | Data carried in the common event. Optional.                |
43  | -h/--help    | Help information.                                  |
44
45* Example
46
47  ```bash
48  # Publish a common event named testevent.
49  cem publish --event "testevent"
50  ```
51
52  ![cem-publish-event](figures/cem-publish-event.png)
53
54  ```bash
55  # Publish an ordered common event named testevent. The result code of the event is 100 and the data carried is "this is data".
56  cem publish -e "testevent" -o -c 100 -d "this is data"
57  ```
58
59  ![cem-publish-all](figures/cem-publish-all.png)
60
61### dump
62
63> **NOTE**
64>
65> The Common Event Manager has two editions: **eng** and **user**. The **dump** command can be used only in the **eng** edition. If it is used in the **user** edition, the message **error: user version cannot use dump** is reported.
66
67* Function
68
69  Displays information about common events.
70
71* Method
72
73  ```
74  cem dump [<options>]
75  ```
76
77  The table below describes the available options.
78
79  | Name      | Description                                    |
80  | ---------- | -------------------------------------------- |
81  | -a/--all   | Information about all common events that have been sent since system startup.|
82  | -e/--event | Information about a specific event.                  |
83  | -h/--help  | Help information.                                    |
84
85* Example
86
87  ```bash
88  # Display details of a common event named testevent.
89  cem dump -e "testevent"
90  ```
91
92  ![cem-dump-e](figures/cem-dump-e.png)
93