How does runtime.getruntime.exec work

The meaning of these exit values depends on the particular operating system. A Win32 error with a value of 2 is a "file not found" error. That makes sense, since javac expects us to follow the program with the source code file to compile. Thus, to circumvent the second pitfall -- hanging forever in Runtime. Under the Windows operating system, many new programmers stumble upon Runtime.

Subsequently, they run into Runtime. As stated earlier, the error value of 2 means "file not found," which, in this case, means that the executable named dir. That's because the directory command is part of the Windows command interpreter and not a separate executable. To run the Windows command interpreter, execute either command. Here are the latest Insider stories. More Insider Sign Out. Sign In Register. Sign Out Sign In Register.

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How to describe Java code with annotations. You need to use the start command. Actually, even I don't see a new command prompt popping up, but you can check that a new cmd. Though, the same functionality can be achieved using Runtime. Those do not work. Your current execution thread will be blocked on process.

Source here. Also note that if process is already terminated : waitFor will not be blocked. More generally if you want to see the data on the pipeline on the go you can use peek or the debugger could also help.

So applied to your example:. The idiomatic way to achieve your task would be to filter the stream and then simply use count :. This one works Asked 3 Months ago Answers: 5 Viewed times. What am I doing wrong? I was able to use the ProcessBuilder in order to run it without just simply failing It parses "command" just fine, but when I add "command mode" java.

IOException: Cannot run program "command mode": java. Sending everything through as a string may work on some systems but fail on others. Process exec String [] cmdarray Executes the specified command and arguments in a separate process. Process exec String [] cmdarray, String [] envp Executes the specified command and arguments in a separate process with the specified environment. Process exec String [] cmdarray, String [] envp, File dir Executes the specified command and arguments in a separate process with the specified environment and working directory.

Process exec String command, String [] envp Executes the specified string command in a separate process with the specified environment. Process exec String command, String [] envp, File dir Executes the specified string command in a separate process with the specified environment and working directory. As of JDK 1. This method is inherently unsafe. It may result in finalizers being called on live objects while other threads are concurrently manipulating those objects, resulting in erratic behavior or deadlock.

Methods inherited from class java. Object clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait Method Detail getRuntime public static Runtime getRuntime Returns the runtime object associated with the current Java application. Most of the methods of class Runtime are instance methods and must be invoked with respect to the current runtime object. Returns: the Runtime object associated with the current Java application.

This method never returns normally. The argument serves as a status code; by convention, a nonzero status code indicates abnormal termination. The virtual machine's shutdown sequence consists of two phases. In the first phase all registered shutdown hooks , if any, are started in some unspecified order and allowed to run concurrently until they finish.

In the second phase all uninvoked finalizers are run if finalization-on-exit has been enabled. Once this is done the virtual machine halts. If this method is invoked after the virtual machine has begun its shutdown sequence then if shutdown hooks are being run this method will block indefinitely.

If shutdown hooks have already been run and on-exit finalization has been enabled then this method halts the virtual machine with the given status code if the status is nonzero; otherwise, it blocks indefinitely.

The System. Parameters: status - Termination status. By convention, a nonzero status code indicates abnormal termination. Thread , removeShutdownHook java. The Java virtual machine shuts down in response to two kinds of events: The program exits normally, when the last non-daemon thread exits or when the exit equivalently, System.

A shutdown hook is simply an initialized but unstarted thread. When the virtual machine begins its shutdown sequence it will start all registered shutdown hooks in some unspecified order and let them run concurrently. When all the hooks have finished it will then run all uninvoked finalizers if finalization-on-exit has been enabled. Finally, the virtual machine will halt. Note that daemon threads will continue to run during the shutdown sequence, as will non-daemon threads if shutdown was initiated by invoking the exit method.

Once the shutdown sequence has begun it can be stopped only by invoking the halt method, which forcibly terminates the virtual machine. Once the shutdown sequence has begun it is impossible to register a new shutdown hook or de-register a previously-registered hook. Attempting either of these operations will cause an IllegalStateException to be thrown. Shutdown hooks run at a delicate time in the life cycle of a virtual machine and should therefore be coded defensively. They should, in particular, be written to be thread-safe and to avoid deadlocks insofar as possible.

They should also not rely blindly upon services that may have registered their own shutdown hooks and therefore may themselves in the process of shutting down. Attempts to use other thread-based services such as the AWT event-dispatch thread, for example, may lead to deadlocks.

Shutdown hooks should also finish their work quickly. When a program invokes exit the expectation is that the virtual machine will promptly shut down and exit. When the virtual machine is terminated due to user logoff or system shutdown the underlying operating system may only allow a fixed amount of time in which to shut down and exit.

It is therefore inadvisable to attempt any user interaction or to perform a long-running computation in a shutdown hook.