input: systemd: Add missing fields (#144)

Signed-off-by: ialidzhikov <i.alidjikov@gmail.com>

Author: ialidzhikov

input/systemd.md

@@ -11,10 +11,12 @@ The plugin supports the following configuration parameters:
 | Path | Optional path to the Systemd journal directory, if not set, the plugin will use default paths to read local-only logs. |  |
 | Max\_Fields | Set a maximum number of fields (keys) allowed per record. | 8000 |
 | Max\_Entries | When Fluent Bit starts, the Journal might have a high number of logs in the queue. In order to avoid delays and reduce memory usage, this option allows to specify the maximum number of log entries that can be processed per round. Once the limit is reached, Fluent Bit will continue processing the remaining log entries once Journald performs the notification. | 5000 |
-| Systemd\_Filter | allows to perform a query over logs that contains a specific Journald key/value pairs, e.g: \_SYSTEMD\_UNIT=UNIT. The Systemd\_Filter option can be specified multiple times in the input section to apply multiple filters as required. |  |
+| Systemd\_Filter | Allows to perform a query over logs that contains a specific Journald key/value pairs, e.g: \_SYSTEMD\_UNIT=UNIT. The Systemd\_Filter option can be specified multiple times in the input section to apply multiple filters as required. |  |
+| Systemd\_Filter\_Type | Define the filter type when *Systemd_Filter* is specified multiple times. Allowed values are _And_ and _Or_. With _And_ a record is matched only when all of the *Systemd_Filter* have a match. With _Or_ a record is matched when any of the *Systemd_Filter* has a match. | Or |
 | Tag | The tag is used to route messages but on Systemd plugin there is an extra functionality: if the tag includes a star/wildcard, it will be expanded with the Systemd Unit file \(e.g: host.\* => host.UNIT\_NAME\). |  |
 | DB | Specify the absolute path of a database file to keep track of Journald cursor. |  |
-| Read\_From\_Tail | Start reading new entries. skip entries already stored in Journald. | false |
+| Read\_From\_Tail | Start reading new entries. Skip entries already stored in Journald. | Off |
+| Strip\_Underscores | Remove the leading underscore of the Journald field (key). For example the Journald field *_PID* becomes the key *PID*. | Off |
 
 ## Getting Started