在 Linux 中使用 Java 执行命令并获取输出 [英] Execute a command in Linux using Java and fetch the output

问题描述

我正在使用 Groovy 在我的 Linux 机器上执行命令并返回输出，但我无法以某种方式使用 | 管道(我认为)或者它可能没有等待命令结束.

I am using Groovy to execute commands on my Linux box and get back the output, but I am not able to use | pipes somehow (I think) or maybe it is not waiting for the command to finish.

我的代码有什么问题或我遗漏了什么?

What is wrong or what am I missing in my code?

我的调用函数:

def test()
{
    String result="N"

    HashMap<String,String> params = IntermediateResults.get("userparams")
    Map env=AppContext.get(AppCtxProperties.environmentVariables)

    def fClass = new GroovyClassLoader().parseClass( new File( 'plugins/infa9/Infa9CommandExecUtil.groovy' ) )
    List<String> frows=["uname -a",
                        "uname -a | awk '{print$2}'",
                        "uname -a | cut -d ' ' -f 2"]
    List<String> resultRows = fClass.newInstance().fetchCommandOutput( params, env, frows )

    return result
}

Infa9CommandExecUtil.groovy 文件内容(更新:添加 exitVal println):

Infa9CommandExecUtil.groovy file content (update: added exitVal println):

package infa9

import java.io.BufferedReader;

public class Infa9CommandExecUtil {
  StringBuffer result

  public Infa9CommandExecUtil() {
    result = new StringBuffer()
  }

  public List<String> fetchCommandOutput( Map<String,String> params, Map env, List<String> rows )
  {

        List<String> outputRows = new ArrayList<String>()
        try
        {
            for(item in rows)
            {
                String temp=item.toString()
                println "CMD:$temp"
                Process proc = Runtime.getRuntime().exec(temp);
                InputStream stdin = proc.getInputStream();
                InputStreamReader isr = new InputStreamReader(stdin);
                BufferedReader br = new BufferedReader(isr);
                String line = null;

                result = new StringBuffer()
                line=null

                int exitVal = proc.waitFor()    //do I need to wait for the thread/process to finish here?

                while ((line = br.readLine()) != null)
                {
                    result.append(line+System.getProperty("line.separator"))    //to maintain the format (newlines)
                }
                String tRes=result
                tRes=tRes.trim()
                println "OUTPUT:$tRes
EXITVAL:$exitVal"

                outputRows.add(tRes)
            }
        }
        catch (IOException io)  {   io.printStackTrace();}
        catch (InterruptedException ie) {ie.printStackTrace();}
    return  outputRows
  }
}

我的输出(更新:添加了 exitVal 值):

My output (update: added exitVal value):

CMD:uname -a
OUTPUT:Linux estilo 2.6.18-128.el5 #1 SMP Wed Dec 17 11:41:38 EST 2008 x86_64 x86_64 x86_64 GNU/Linux
EXITVAL:0
CMD:uname -a | awk '{print$2}'
OUTPUT:
EXITVAL:1
CMD:uname -a | cut -d ' ' -f 2
OUTPUT:
EXITVAL:1

注意:我在内部使用 sh -c .

Note: I am internally using sh -c <command>.

推荐答案

您不能使用 String.execute() 进行管道或重定向.这在 Java 中不起作用，因此在 Groovy 中也不起作用......

You cannot do pipes or redirects using String.execute(). This doesn't work in Java, so it doesn't work in Groovy either...

你可以使用 Process.pipeTo 和 Groovy 来简化事情:

You can use Process.pipeTo with Groovy to simplify things:

Process proca = 'uname -a'.execute()
Process procb = 'awk {print$2}'.execute()

(proca | procb).text

更通用的版本可能是:

String process = 'uname -a | awk {print$2}'

// Split the string into sections based on |
// And pipe the results together
Process result = process.tokenize( '|' ).inject( null ) { p, c ->
  if( p )
    p | c.execute()
  else
    c.execute()
}
// Print out the output and error streams
result.waitForProcessOutput( System.out, System.out )

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