在Java中执行shell脚本并读取输出

Question

我在java中使用下面的方法执行shell脚本

public static void main(String ar[])
{
  //key value are being read from properties file, here I am assigning the sample values      directly

   key=mine
   value="ls-1|tail-1"


  String[] cmd = { "jj.sh" , key,value};
  Process script_exec = Runtime.getRuntime().exec(cmd);
  script_exec.waitFor();
  if(script_exec.exitValue() != 0){
   System.out.println("Error while executing script");

  BufferedReader stdInput = new BufferedReader(new
                InputStreamReader(script_exec.getInputStream()));

  while ((s = stdInput.readLine()) != null) {
                System.out.println(s);
            }
}

jj.sh文件包含以下值

#!/bin/sh

key=$1
value=`$2` 
echo $value

当我直接使用key和value执行jj.sh时,它会给我正确的值,即文件名.但是对于java,它给我结果为ls -1 result(表示java忽略'|'之后的命令).当我传递用波形符号`分隔的键值时,它只显示完整的键值即ls -1|tail -1

如何使用java执行完整命令

Answer 1

这不起作用的主要原因`$2`是`ls -1 | tail -1`,即使$2设置为该字符串,也不一样.

如果脚本接受带有要执行的命令的文字字符串,则可以使用eval这样做.

我创建了一个完整的例子.在您尝试将其中任何一个应用到您自己的代码之前,请复制粘贴并验证它是否有效.这是Test.java:

import java.io.*;                                                            

public class Test {                                                          
  public static void main(String[] args) throws Exception {                  
    String[] command = { "./myscript", "key", "ls -t | tail -n 1" };         
    Process process = Runtime.getRuntime().exec(command);                    
    BufferedReader reader = new BufferedReader(new InputStreamReader(        
        process.getInputStream()));                                          
    String s;                                                                
    while ((s = reader.readLine()) != null) {                                
      System.out.println("Script output: " + s);                             
    }                                                                        
  }                                                                          
}      

而且myscript:

#!/bin/bash                                
key="$1"                                   
value=$(eval "$2")                             
echo "The command  $2  evaluated to: $value" 

以下是我们如何myscript单独运行:

$ ls -t | tail -n 1
Templates

$ ./myscript foo 'ls -t | tail -n 1'
The command  ls -t | tail -n 1  evaluated to: Templates

这是运行Java代码的结果:

$ javac Test.java && java Test
Script output: The command  ls -t | tail -n 1  evaluated to: Templates