Java如何调用shell脚本的

有些时候会碰到这样的场景：java的功能里面要嵌入一个功能点，这个功能是通过是shell脚本实现的。这种时候就需要Java对脚本调用的支持了。

测试环境

Ubuntu16.04 i3-6100,12GB

Hello World

来看一个基本的例子

    Process exec = Runtime.getRuntime().exec(new String[] { "uname" ,"-a"});
    exec.waitFor();
    BufferedReader reader =
            new BufferedReader(new InputStreamReader(exec.getInputStream()));
    System.out.println(reader.readLine());

Linux jason-Inspiron-3650 4.4.0-121-generic #145-Ubuntu SMP Fri Apr 13 13:47:23 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

解读Process

java.lang.Process类提供了获取输入、输出、等待执行和销毁进程的方法。

Process类可通过ProcessBuilder.start() 和 Runtime.exec 创建实例，从Java1.5开始，ProcessBuilder.start()是更推荐的做法，但网上的教程更多推荐用Runtime.exec()方法。

Modifier and Type	Method	Description
abstract void	destroy ()	Kills the subprocess.
abstract int	exitValue ()	Returns the exit value for the subprocess.
abstract InputStream	getErrorStream ()	Returns the input stream connected to the error output of the subprocess.
abstract InputStream	getInputStream ()	Returns the input stream connected to the normal output of the subprocess.
abstract OutputStream	getOutputStream ()	Returns the output stream connected to the normal input of the subprocess.
abstract int	waitFor ()	Causes the current thread to wait, if necessary, until the process represented by this Process object has terminated.

继承体系上面，Process的实现类是JDK内置的，linux版本的jdk中只带有一个实现类UnixProcess。

与脚本交互

Process不但可以执行进程，还可以获取进程的返回结果。

    private String executeCommand(String command) {
        StringBuffer output = new StringBuffer();
        Process p;
        try {
            p = Runtime.getRuntime().exec(command);
            int exitCode = p.waitFor();
            System.out.println(exitCode);
            BufferedReader reader =
                    new BufferedReader(new InputStreamReader(p.getInputStream()));
            String line = "";
            while ((line = reader.readLine()) != null) {
                output.append(line + "\n");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println(output.toString());
        return output.toString();
    }

PING www.a.shifen.com (111.13.100.91) 56(84) bytes of data.
64 bytes from localhost (111.13.100.91): icmp_seq=1 ttl=52 time=7.66 ms
64 bytes from localhost (111.13.100.91): icmp_seq=2 ttl=52 time=7.90 ms
64 bytes from localhost (111.13.100.91): icmp_seq=3 ttl=52 time=14.0 ms

--- www.a.shifen.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 7.668/9.861/14.013/2.937 ms

总结

Java 执行脚本的方式其实类似用直接在bash里面执行脚本，区别在于环境有些变动，执行的效果和bash基本一致。

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