Java如何调用shell脚本的

Posted 2021-04-24 可乐小数据

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

```java

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。

```java

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。