Java Runtime.getRuntime（）：从执行命令行程序获取输出

我正在使用运行时从Java程序运行命令提示符命令。但是，我不知道如何获得命令返回的输出。

这是我的代码：

Runtime rt = Runtime.getRuntime();

String[] commands = {"system.exe", "-send" , argument};

Process proc = rt.exec(commands);

我尝试做，System.out.println(proc);但是没有返回任何东西。该命令的执行应返回两个数字，以分号分隔。我怎样才能在变量中打印出来？

这是我现在使用的代码：

String[] commands = {"system.exe", "-get t"};

Process proc = rt.exec(commands);

InputStream stdIn = proc.getInputStream();
InputStreamReader isr = new InputStreamReader(stdIn);
BufferedReader br = new BufferedReader(isr);

String line = null;
System.out.println("<OUTPUT>");

while ((line = br.readLine()) != null)
     System.out.println(line);

System.out.println("</OUTPUT>");
int exitVal = proc.waitFor();
System.out.println("Process exitValue: " + exitVal);

但是我没有得到任何输出，但是当我自己运行该命令时，它可以正常工作。

这是要走的路：

Runtime rt = Runtime.getRuntime();
String[] commands = {"system.exe", "-get t"};
Process proc = rt.exec(commands);

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

BufferedReader stdError = new BufferedReader(new 
     InputStreamReader(proc.getErrorStream()));

// Read the output from the command
System.out.println("Here is the standard output of the command:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
    System.out.println(s);
}

// Read any errors from the attempted command
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null) {
    System.out.println(s);
}

在此处阅读Javadoc以获得更多详细信息。ProcessBuilder将是一个很好的选择。

更快的方法是这样的：

public static String execCmd(String cmd) throws java.io.IOException {
    java.util.Scanner s = new java.util.Scanner(Runtime.getRuntime().exec(cmd).getInputStream()).useDelimiter("\\A");
    return s.hasNext() ? s.next() : "";
}

基本上，这是它的精简版：

public static String execCmd(String cmd) throws java.io.IOException {
    Process proc = Runtime.getRuntime().exec(cmd);
    java.io.InputStream is = proc.getInputStream();
    java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
    String val = "";
    if (s.hasNext()) {
        val = s.next();
    }
    else {
        val = "";
    }
    return val;
}

我知道这个问题很旧，但是我发布这个答案是因为我认为这可能会更快。

除了ProcessBuilder按照建议的方式使用Senthil之外，请务必阅读并实现When Runtime.exec（）will not not的所有建议。

如果在类路径中已经可以使用Apache commons-io，则可以使用：

Process p = new ProcessBuilder("cat", "/etc/something").start();
String stderr = IOUtils.toString(p.getErrorStream(), Charset.defaultCharset());
String stdout = IOUtils.toString(p.getInputStream(), Charset.defaultCharset());

我们也可以使用流来获取命令输出：

public static void main(String[] args) throws IOException {

        Runtime runtime = Runtime.getRuntime();
        String[] commands  = {"free", "-h"};
        Process process = runtime.exec(commands);

        BufferedReader lineReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        lineReader.lines().forEach(System.out::println);

        BufferedReader errorReader = new BufferedReader(new InputStreamReader(process.getErrorStream()));
        errorReader.lines().forEach(System.out::println);
    }

提到@Senthil和@Arend答案（https://stackoverflow.com/a/5711150/2268559）ProcessBuilder。这是ProcessBuilder为命令指定环境变量和工作文件夹的示例：

    ProcessBuilder pb = new ProcessBuilder("ls", "-a", "-l");

    Map<String, String> env = pb.environment();
    // If you want clean environment, call env.clear() first
    //env.clear();
    env.put("VAR1", "myValue");
    env.remove("OTHERVAR");
    env.put("VAR2", env.get("VAR1") + "suffix");

    File workingFolder = new File("/home/user");
    pb.directory(workingFolder);

    Process proc = pb.start();

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

    BufferedReader stdError = new BufferedReader(new InputStreamReader(proc.getErrorStream()));

    // Read the output from the command:
    System.out.println("Here is the standard output of the command:\n");
    String s = null;
    while ((s = stdInput.readLine()) != null)
        System.out.println(s);

    // Read any errors from the attempted command:
    System.out.println("Here is the standard error of the command (if any):\n");
    while ((s = stdError.readLine()) != null)
        System.out.println(s);

在撰写本文时，所有其他包含代码的答案都可能导致死锁。

工艺具有用于限制缓冲器stdout和stderr输出。如果您不同时收听它们，那么当您尝试阅读另一种时，它们中的一种会变满。例如，stdout当进程正在等待写入时，您可能正在等待读取stderr。您无法从stdout缓冲区读取数据，因为它为空，并且进程无法写入stderr缓冲区，因为它已满。你们彼此永远在等待。

这是一种在没有死锁风险的情况下读取进程输出的可能方法：

public final class Processes
{
    private static final String NEWLINE = System.getProperty("line.separator");

    /**
     * @param command the command to run
     * @return the output of the command
     * @throws IOException if an I/O error occurs
     */
    public static String run(String... command) throws IOException
    {
        ProcessBuilder pb = new ProcessBuilder(command).redirectErrorStream(true);
        Process process = pb.start();
        StringBuilder result = new StringBuilder(80);
        try (BufferedReader in = new BufferedReader(new InputStreamReader(process.getInputStream())))
        {
            while (true)
            {
                String line = in.readLine();
                if (line == null)
                    break;
                result.append(line).append(NEWLINE);
            }
        }
        return result.toString();
    }

    /**
     * Prevent construction.
     */
    private Processes()
    {
    }
}

关键是要使用ProcessBuilder.redirectErrorStream(true)它将重定向stderr到stdout流中。这样一来，您无需在stdout和之间切换即可读取单个流stderr。如果要手动实现此功能，则必须在两个不同的线程中使用流，以确保永不阻塞。

如果您在Kotlin上书写，则可以使用：

val firstProcess = ProcessBuilder("echo","hello world").start()
val firstError = firstProcess.errorStream.readBytes().decodeToString()
val firstResult = firstProcess.inputStream.readBytes().decodeToString()

改编自先前的答案：

public static String execCmdSync(String cmd, CmdExecResult callback) throws java.io.IOException, InterruptedException {
    RLog.i(TAG, "Running command:", cmd);

    Runtime rt = Runtime.getRuntime();
    Process proc = rt.exec(cmd);

    //String[] commands = {"system.exe", "-get t"};

    BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream()));
    BufferedReader stdError = new BufferedReader(new InputStreamReader(proc.getErrorStream()));

    StringBuffer stdOut = new StringBuffer();
    StringBuffer errOut = new StringBuffer();

    // Read the output from the command:
    System.out.println("Here is the standard output of the command:\n");
    String s = null;
    while ((s = stdInput.readLine()) != null) {
        System.out.println(s);
        stdOut.append(s);
    }

    // Read any errors from the attempted command:
    System.out.println("Here is the standard error of the command (if any):\n");
    while ((s = stdError.readLine()) != null) {
        System.out.println(s);
        errOut.append(s);
    }

    if (callback == null) {
        return stdInput.toString();
    }

    int exitVal = proc.waitFor();
    callback.onComplete(exitVal == 0, exitVal, errOut.toString(), stdOut.toString(), cmd);

    return stdInput.toString();
}

public interface CmdExecResult{
    void onComplete(boolean success, int exitVal, String error, String output, String originalCmd);
}

与此页面上的其他片段几乎相同，但只是将功能组织起来，我们开始...

String str=shell_exec("ls -l");

类函数：

public String shell_exec(String cmd)
       {
       String o=null;
       try
         {
         Process p=Runtime.getRuntime().exec(cmd);
         BufferedReader b=new BufferedReader(new InputStreamReader(p.getInputStream()));
         String r;
         while((r=b.readLine())!=null)o+=r;
         }catch(Exception e){o="error";}
       return o;
       }

尝试阅读InputStream运行时的：

Runtime rt = Runtime.getRuntime();
String[] commands = {"system.exe", "-send", argument};
Process proc = rt.exec(commands);
BufferedReader br = new BufferedReader(
    new InputStreamReader(proc.getInputStream()));
String line;
while ((line = br.readLine()) != null)
    System.out.println(line);

proc.getErrorStream()如果该进程正在打印错误输出，则可能还需要读取错误流（）。如果使用，您可以将错误流重定向到输入流ProcessBuilder。