从unix设备读取数据

发布于 2024-09-05 17:10:02 字数 698 浏览 6 评论 0原文

在我的一台 RedHat Linux 服务器上已经设置了几个设备。 /dev/ap 和 /dev/reuter。它们是美联社和路透社的新闻源。在unix命令行中，我可以执行“cat /dev/ap”，它会等待，直到一条消息出现在提要中并将其打印到标准输出。一旦流中出现暂停，猫就会完成。我尝试了“更多”并得到了相同的结果，与 less -f （完整的消息，可能是运气）相同，并且 tail -f 在一个小时内没有输出。

我知道这些是流，但是当我尝试在 new Reader("/dev/ap") 上打开 Java BufferReader 时，我没有得到任何输出。使用以下运行方法：

public void run() {
    String line = null;
    while(true) {
        try {
            while((line = bsr.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

几个问题：
1. 某些unix命令是否仅限于从文件中打开流？例如尾巴？ 2.我在Java端做错了什么，导致我无法捕获输出？错误的流类型、错误的包装器类型？吉姆

原文

On one of my RedHat Linux Servers a couple devices have been setup. /dev/ap and /dev/reuter. They are AP and Reuters news feeds. At the unix command line I can do "cat /dev/ap" and it waits until a message comes down the feed and prints it out to stdout. As soon as there is a pause in the stream cat completes. I tried "more" and got the same results, same with less -f (complete msg, could be luck) and tail -f had no output in an hour.

I know these are streams, but when I try to open a Java BufferReader on new Reader("/dev/ap") I get no output. Using the following run method:

public void run() {
    String line = null;
    while(true) {
        try {
            while((line = bsr.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Couple questions:
1. Are some of the unix commands limited to opening streams from files? e.g. tail?
2. What Am I doing wrong on the Java side that I can't capture the output?
Wrong stream type, wrong wrapper type?
Jim

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初熏 2024-09-12 17:10:02

您的方法似乎不错，但是 readLine() 对于一行文本的构成非常讲究。您可以查看原始流：

cat /dev/ap | hexdump -C

您也可以尝试 read()，如从 /dev/zero 读取的片段所示：

BufferedReader in = new BufferedReader(new FileReader("/dev/zero"));
for (int i = 0; i < 10; i++) {
    System.out.print(in.read() + " ");
}
System.out.println();
in.close();

附录：对于串行 I/O，请考虑RXTX 或类似库。

Your approach seems sound, but readLine() is very particular about what constitutes a line of text. You might look at the raw stream:

cat /dev/ap | hexdump -C

You could also try read(), as seen in this fragment that reads from /dev/zero:

BufferedReader in = new BufferedReader(new FileReader("/dev/zero"));
for (int i = 0; i < 10; i++) {
    System.out.print(in.read() + " ");
}
System.out.println();
in.close();

Addendum: For serial I/O, consider RXTX or similar libraries.

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