System.getenv（）和amp System.getProperty（） [英] Difference between System.getenv() & System.getProperty()

问题描述

可能重复：

系统属性和环境变量之间有什么区别？

Possible Duplicate:
What’s the difference between a System property and environment variable

What is the difference between System.getenv() & System.getProperty()?

当我们使用Processbuilder运行任何命令时，我们可以设置环境变量ie：

When we run any command using Processbuilder, we can set the environment variables ie:

String[] vCmd = { System.getenv("ANT_HOME") + "/bin/ant", "-f",
                ANT_BUILD_FILE, TARGET };
        ProcessBuilder pb = new ProcessBuilder(vCmd);
        Map<String, String> env = pb.environment();     
        env.put("CLASSPATH",
                antHome+"/lib/ant.jar:"
                        + antHome+"/lib/ant-launcher.jar:"
                        + antHome+"/lib/ant-nodeps.jar:"
                        );
        try{

            Process process = pb.start();
            InputStream is = process.getInputStream();
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader br = new BufferedReader(isr);
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
            pb.wait();
        }
        catch(Exception e)

            System.out.println(e.getMessage());


        }

如果我使用System设置一些属性。这个方法之前的setProperties（）是否可以由ProcessBuilder启动的这个进程可用？

If I set some properties using System.setProperties() before this method , is it available to this process started by ProcessBuilder?

推荐答案

getenv 获取一个环境变量。 getProperty 获取Java属性。环境变量在OS级别指定。通过将 -D 选项传递给JVM来指定Java属性（可以通过编程方式设置）。

getenv gets an environment variable. getProperty gets a Java property. Environment variables are specified at the OS level. Java properties are specified by passing the -D option to the JVM (and can be set programmatically).

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