question: public InstanceProcess exec ( String workspaceId , String machineId , Command command , @ Nullable String outputChannel ) throws NotFoundException , MachineException , BadRequestException { requiredNotNull ( machineId , "Machine ID is required" ) ; requiredNotNull ( command , "Command is required" ) ; requiredNotNull ( command . getCommandLine ( ) , "Command line is required" ) ; requiredNotNull ( command . getName ( ) , "Command name is required" ) ; requiredNotNull ( command . getType ( ) , "Command type is required" ) ; final Instance machine = environmentEngine . getMachine ( workspaceId , machineId ) ; final InstanceProcess instanceProcess = machine . createProcess ( command , outputChannel ) ; final int pid = instanceProcess . getPid ( ) ; final LineConsumer processLogger = getProcessLogger ( machineId , pid , outputChannel ) ; executor . execute ( ThreadLocalPropagateContext . wrap ( null ) ) ; return instanceProcess ; }
target:  Execute a command in machine