# Exec Binding

This binding integrates the possibility to execute arbitrary shell commands.

## Supported Things

Currently, the binding supports a single type of Thing, being the `command` Thing.

## Binding Configuration

For security reasons all commands need to be whitelisted.
Allowed commands need to be added to the `misc/exec.whitelist` file in the configuration directory.
Every command needs to be on a separate line.

Example:

```shell
/bin/echo "Hello world!"
/usr/local/bin/apcaccess status
php ./configurations/scripts/script.php %2$s
```

**Linux:**
Note that the commands are executed in the context and with the privileges of the process running the Java Virtual Machine.
On a Linux system the system user `openhab` needs to have the privileges needed to execute your intended command.
It is advised to test the correct operation of the command in the scope of the `openhab` user on the command line first:

```shell
sudo -u openhab <YOUR COMMAND>
```

It is not advised to run the virtual machine as superuser/root.

## Thing Configuration

The "command" Thing requires the command to execute on the shell.
Optionally one can specify:

- `transform` - A [transformation](https://www.openhab.org/docs/configuration/transformations.html) to apply on the execution result string.
- `interval` - An interval, in seconds, the command will be repeatedly executed. Default is 60 seconds, set to 0 to avoid automatic repetition.
- `timeout` - A time-out, in seconds, the execution of the command will time out, and lastly,
- `autorun` - A boolean parameter to make the command execute immediately every time the input channel is sent a different openHAB command. If choosing autorun, you may wish to also set `interval=0`. Note that sending the same command a second time will not trigger execution.

For each shell command, a separate Thing has to be defined.

```java
Thing exec:command:uniquename [command="/command/to/execute here", interval=15, timeout=5, autorun=false]
```

The `command` itself can be enhanced using the well known syntax of the [Java formatter class syntax](https://docs.oracle.com/javase/8/docs/api/java/util/Formatter.html#syntax).
The following parameters are automatically added:

-   the current date (as java.util.Date, example: `%1$tY-%1$tm-%1$td`)
-   the current (or last) command to the input channel (see below, example: `%2$s`)

note - if you trigger execution using interval or the run channel, the `%2` substitution will use the most recent command (if there has been one) sent to the input channel.  The state of the Item linked to input channel is ignored.

## Channels

All Things support the following channels:

| Channel Type ID | Item Type | Description                                                                          |
|-----------------|-----------|--------------------------------------------------------------------------------------|
| input           | String    | Input parameter to provide to the command                                            |
| output          | String    | Output of the last execution of the command                                          |
| exit            | Number    | The exit value of the last execution of the command                                  |
| run             | Switch    | Send ON to execute the command, the current state tells whether it is running or not |
| lastexecution   | DateTime  | Time/Date the command was last executed, in yyyy-MM-dd'T'HH:mm:ss.SSSZ format        |

**Attention:** Linking `input` to any other item type than `String` will result in erroneous behavior.
If needed, please use a rule to convert your item's state to a string.
Also note that only commands (e.g. `sendCommand`) to the `input` channel are recognized, updating the item's state will not work (e.g. `postUpdate`).

## Minimal Example

**demo.things**

```java
Thing exec:command:apc [command="/usr/local/bin/apcaccess status", interval=15, timeout=5]
Thing exec:command:myscript [command="php ./configurations/scripts/script.php %2$s", transform="REGEX((.*?))"]
```

**demo.items**

```java
String APCRaw "[%s]" (All) {channel="exec:command:apc:output"}
Switch APCRunning {channel="exec:command:apc:run"}
Number APCExitValue "[%d]" {channel="exec:command:apc:exit"}
DateTime APCLastExecution {channel="exec:command:apc:lastexecution"}
```

## Full Example

Following is an example how to set up an exec command thing, pass it a parameter, debug it with a rule and set the returned string to an Number Item. 

**demo.things**

```java
// "%2$s" will be replace by the input channel command, this makes it possible to use one command line with different arguments.
// e.g: "ls" as <YOUR COMMAND> and "-a" or "-l" as additional argument sent to the input channel in the rule.
Thing exec:command:yourcommand [ command="<YOUR COMMAND> %2$s", interval=0, autorun=false ]
```

**demo.items**

```java
Switch YourTrigger "External trigger [%s]"
Number YourNumber "Your Number [%.1f °C]"

// state of the execution, is running or finished
Switch yourcommand_Run {channel="exec:command:yourcommand:run", autoupdate="false"}
// Arguments to be placed for '%2$s' in command line
String yourcommand_Args {channel="exec:command:yourcommand:input"}
// Output of command line execution 
String yourcommand_Out {channel="exec:command:yourcommand:output"}
```

**demo.sitemap**

```java
// Name of file and name of sitemap has to be the same
sitemap demo label="Your Value"
{
        Frame {
            Switch item=YourTrigger
            Text item=YourNumber
        }
}
```

**demo.rules**

```java
rule "Set up your parameters"
when
   Item YourTrigger changed
then
      // here we can take different actions according to source Item
   if(YourTrigger.state == ON){
      yourcommand_Args.sendCommand("Additional Argument to command line for ON")
   }else{
      yourcommand_Args.sendCommand("Different Argument to command line for OFF")
   }
      // Caution : openHAB bus is asynchronous
      // we must let the command work before triggering execution (if autorun false)
end

rule "begin your execution"
when
   Item yourcommand_Args received command
then
      // Separately triggering RUN allows subsequent executions with unchanged parameter %2
      // which autorun does not.
   if (yourcommand_Run.state != ON) {
      yourcommand_Run.sendCommand(ON)
         // the Run indicator state will go ON shortly, and return OFF when script finished
   }else{
      logInfo("Your command exec", "Script already in use, skipping execution.")
   }
end

rule "script complete"
when
   Item yourcommand_Run changed from ON to OFF
then
      // Logging of ending
   logInfo("Your command exec", "Script has completed.")
      // Caution : openHAB bus is asynchronous
      // there is no guarantee the output Item will get updated before the run channel triggers rules
end

rule "process your results"
when
   Item yourcommand_Out received update
then
      // Logging of raw command line result
   logInfo("Your command exec", "Raw result:" + yourcommand_Out.state )
      // If the returned string is just a number it can be parsed
      // If not, a regex or another transformation could be used
   YourNumber.postUpdate(Integer::parseInt(yourcommand_Out.state.toString) as Number)
end

```

## Source

[openHAB community thread with a detailed example.](https://community.openhab.org/t/1-openhab-433mhz-radio-transmitter-tutorial/34977)
