Executing commands with Gradle?

Question

I am trying to execute a command with gradle with the below task: ``` task stopServer(dependsOn: war, type: Exec) << { commandLine 'pkill -9 tomcat' } ``` When I run it I get the following error: ``` * What went wrong: Execution failed for task ':stopServer'. > execCommand == null! ``` And when my task is like this: ``` task stopServer(dependsOn: war) << { exec { commandLine 'pkill -9 tomcat' } } ``` I get this error: ``` * What went wrong: Execution failed for task ':stopServer'. > A problem occurred starting process 'command 'pkill -9 tomcat'' ``` Can you tell me where I am going wrong in each of these approaches? If neither of above are right way of executing then please specify the way of doing it probably with an example.

Accepted Answer

I believe you're looking for this:

```
task stopServer(dependsOn: war, type: Exec) {
     commandLine "pkill", " -9", "tomcat"
}
```

The main difference is very subtle - I just deleted two characters. The `<<` is gone from the task definition. The other difference is that the `commandLine` expects the executable to be passed in separately from the arguments to it.

I removed the `<<` because of an important idea in gradle: the build lifecycle. There's configuration and execution phases (that's not all, but it's enough to explain this).

The `<<` is like saying `doLast` - it adds the closure you pass to the end of the actions (the execution phase) for this task. So that means here, it's going to try and execute the command like normal (it's an `Exec` object, after all), and only then, once it's executed, will it call your block - the block setting `commandLine`. So when it's executing, `execCommand` really is null, and would be until your block was run. This is the heart of your problem.

Without the `<<` (also known as left-shift), that same block runs during the configuration phase. So the exec command gets set before it runs, and it works.

Executing commands with Gradle?

Solution

Problem