虽然我们知道在编写java程序时,只有线程的概念,依托于JVM这个进程,但是API提供了Runtime这个类,(Every Java application has a single instance of class Runtime that allows the application to interface with the environment in which the application is running. The
current runtime can be obtained from the getRuntime method.An application cannot create its own instance of this class.)使得出现了子进程,通过getRuntime.exec()可以用来执行shell脚本。原理就是:会从当前虚拟机进程fork一个子进程,然后用新的进程执行命令,而后退出。所以当太多这种场景的时候会出现大量进程,会成为问题,所以能用java API完成的就不要使用这种方式。理解:子进程当然有管道的概念,所以明确了这一点,就可以从中得到InputStream/OutputStream进行一些有用操作。
下面是一个简单的示例:
import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; //Executes the specified string command in a separate process. public class TestRuntime { public static void main(String[] args) throws IOException { Runtime r = Runtime.getRuntime(); Process p = r.exec("man ls"); System.out.println(p.isAlive()); BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream())); String res ; while((res = br.readLine()) != null){ System.out.println(res); } } }
结果:
时间: 2024-07-31 23:00:02