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The Runtime.exec methods create a native process and
return an instance of a subclass of Process that can
be used to control the process and obtain information about it.
The class Process provides methods for performing
input from the process, performing output to the process, waiting
for the process to complete, checking the exit status of the process,
and destroying (killing) the process.
The Runtime.exec methods may not work well for special
processes on certain native platforms, such as native windowing
processes, daemon processes, Win16/DOS processes on Microsoft Windows, or shell
scripts. The created subprocess does not have its own terminal or
console. All its standard io (i.e. stdin, stdout, stderr) operations
will be redirected to the parent process through three streams
(Process.getOutputStream(),
Process.getInputStream(),
Process.getErrorStream()).
The parent process uses these streams to feed input to and get output
from the subprocess. Because some native platforms only provide
limited buffer size for standard input and output streams, failure
to promptly write the input stream or read the output stream of
the subprocess may cause the subprocess to block, and even deadlock.
The subprocess is not killed when there are no more references to
the Process object, but rather the subprocess
continues executing asynchronously.
There is no requirement that a process represented by a Process
object execute asynchronously or concurrently with respect to the Java
process that owns the Process object.
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