External commands, e.g. compilers, can be executed using the External template:

external 'javac ' id '.java' execute

Again, all output between external and execute keywords goes to building up the command to be executed. For example, the command above would run a Java compiler on a .java file named after the current object, e.g. ‘javac Stopwatch.java’. Commands are executed immediately they are encountered, and the generator continues executing without waiting for the command to return.

To block generator execution during the external command, substitute the final execute command with an executeBlocking command, i.e.

external 'javac ' id '.java' executeBlocking

Note that executeBlocking can only work for programs, i.e. something that exists as an executable (e.g. .exe, .com or .bat on Windows); execute also works with URLs, documents, and internal DOS commands such as mkdir. To use executeBlocking for non-programs, you can make a command that invokes the platform’s command processor or a script like metarun. E.g. the following would work in Windows:

external 'start "" cmd /x /c mkdir NEW' executeBlocking

A useful resource for command processors, batch files and shell scripts is www.ss64.com.