Question

我正在使用Groovy在我的Linux机器上执行命令并取回输出，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完成。

我的代码中有什么问题或我缺少什么？

我的通话功能：

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：添加了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:$tRes\nEXITVAL:$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）：

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 <command>。

Answer 1

您无法使用String.execute()进行管道或重定向。这在Java中不起作用，因此它在Groovy中也不起作用......

您可以将Process.pipeTo与Groovy一起使用来简化操作：

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 )

Answer 2

管道|是bash之类的shell的一个特性。要使用管道，您需要运行shell，例如

"/bin/bash", "-c", "uname -a | awk '{print $2}'"

要使用ProcessBuilder进行重定向，您可以执行

public static void main(String... args) throws IOException, InterruptedException {
    final String cmd = "uname -a | awk '{print $1 \" \" $3}'";
    System.out.println(cmd + " => " + run(cmd));
}

private static String run(String cmd) throws IOException, InterruptedException {
    final ProcessBuilder pb = new ProcessBuilder("/bin/bash", "-c", cmd);
    pb.redirectErrorStream();
    final Process process = pb.start();
    final InputStream in = process.getInputStream();
    final byte[] bytes = new byte[1024];
    final ByteArrayOutputStream baos = new ByteArrayOutputStream();

    // you must read the output as the program runs or it can stall.
    for (int len; (len = in.read(bytes)) > 0;)
        baos.write(bytes, 0, len);
    process.waitFor();
    return baos.toString(); // assuming the default char encoding is ok.
}

打印

uname -a | awk '{print $1 " " $3}' => Linux 2.6.18-274.3.1.el5

Answer 3

管道是shell的一个特性。因此，如果要支持管道，则必须在shell上下文中运行命令，即在java中传递给exec的命令行应该看起来像/bin/sh YOUR_COMMAND。

使用Java在Linux中执行命令并获取输出

3 个答案: