java runtime.getruntime()从执行命令行程序获取输出

Question

我正在使用运行时从我的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);

我尝试过,System.out.println(proc);但没有返回任何东西.该命令的执行应返回由分号分隔的两个数字,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);

但我没有得到任何东西作为我的输出,但当我自己运行该命令它工作正常.

Answer 1

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);
}

更好地阅读更多细节的Javadoc 在这里.ProcessBuilder是一个很好的选择

Answer 2

更快的方法是:

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() : "";
}

这基本上是这个的浓缩版本:

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;
}

我知道这个问题已经过时但是我发布了这个答案,因为我觉得这可能会更快.

Answer 3

除了使用ProcessBuilderSenthil建议之外,请务必阅读并实现Runtime.exec()不会的所有建议.

Answer 4

在撰写本文时，所有其他包含代码的答案都可能导致死锁。

进程有一个有限的缓冲区stdout和stderr输出。如果您不同时听它们，当您尝试阅读另一个时，其中一个会填满。例如，您可能正在等待读取stdout而进程正在等待写入stderr. 您无法读取stdout缓冲区，因为它是空的，并且进程无法写入stderr缓冲区，因为它已满。你们每个人都在永远地等待对方。

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()
    {
    }
}

关键是使用ProcessBuilder.redirectErrorStream(true)which 将重定向stderr到stdout流中。这允许您读取单个流而无需在stdout和之间交替stderr。如果您想手动实现这一点，您将不得不在两个不同的线程中使用流以确保您永远不会阻塞。

Answer 5

@Senthil和@Arend回答(/sf/answers/399780531/)提到了ProcessBuilder.以下是使用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);

Answer 6

如果已经在类路径上使用了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());

Answer 7

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);
    }