通过命名管道发送结构化数据 (Linux)

发布于 2024-09-14 05:10:46 字数 682 浏览 5 评论 0原文

我在 Debian 系统上使用命名管道进行 IPC。我将把一些数据作为一组字符串从 bash 脚本发送到用 C 代码编写的后台运行进程。

我要发送的数据是四个字符串，例如 accountid、名字、姓氏、描述。目前，我将数据作为 bash 脚本中用空格分隔的字符数组发送。

echo "accountid firstname surname description" >$pipe

在后台进程中，我将这样的管道数据读入字符数组“datain”中

res = read(pipe_fd, datain, BUFFER_SIZE);

，然后我只是在数组上迭代，寻找空格

等

char* p = datain;

char accountid[80];
char firstname[80];

// extract the accountid
while(p!='')
{
    accountid = p;
    ++p;
}

++p;

while(p!='')
{
    firstname = p;
    ++p;
}

......

这种方法似乎有点粗糙，但是我的编程技能不是那么好，所以我想知道是否有更好的策略通过 Linux 中的命名管道传输这组数据。

谢谢

原文

i am using a named pipe for IPC on a Debian system. I will be sending some data as a set of strings from a bash script to a background running process written in C code.

The data i want to send is four strings eg accountid, firstname,surname, description. Currently i am sending the data as a char array separated by spaces from my bash script.

echo "accountid firstname surname description" >$pipe

In the background process i read the pipe data like this into char array 'datain'

res = read(pipe_fd, datain, BUFFER_SIZE);

then i am just iterating over the array looking for spaces

char* p = datain;

char accountid[80];
char firstname[80];

// extract the accountid
while(p!='')
{
    accountid = p;
    ++p;
}

++p;

while(p!='')
{
    firstname = p;
    ++p;
}

etc....

This method seems a bit crude however my programming skills are not that good so i was wondering if there was a better strategy for transferring this set of data over a named pipe in Linux.

Thanks

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撩人痒 2024-09-21 05:10:46

管道（命名或未命名）是字节流。如果双方使用相同的语言，则可能有更好的方法来发送结构化数据。在您的情况下，像您所做的那样，手动编码和解码是迄今为止最简单的解决方案。
不要使用空格来分隔可能包含空格的字段，例如人名。使用 :，例如 /etc/passwd。
在 C 中，read 很难使用，因为您必须提前决定缓冲区大小并且您必须在循环中调用它，因为它可能会返回突发奇想小于缓冲区大小。 stdio.h 中的函数（作用于 FILE* 而不是文件描述符）更易于使用，但仍需要处理长行。如果您不关心 Linux 之外的可移植性，请使用 getline：
```
FILE *pipe = fdopen(fd, "r");
字符*行= NULL；
size_t 线长度；
getline(&line, &line_length, 管道);
```

然后使用 strchr 定位行中的 :。（不要尝试使用 strtok，它仅适用于不能为空的空格分隔字段。）

A pipe (named or not) is a stream of bytes. If you were using the same language on both sides, there might be a better way of sending structured data. In your situation, a manual encoding and decoding, like you're doing, is by far the easiest solution.
Don't use spaces to separate fields that may contain spaces, such as people's names. Use :, like /etc/passwd.
In C, read is hard to use, because you have to decide on a buffer size in advance and you have to call it in a loop because it may return less than the buffer size on a whim. The functions from stdio.h (that operate on a FILE* rather than a file descriptor) are easier to use but still require work to handle long lines. If you don't care about portability outside Linux, use getline:
```
FILE *pipe = fdopen(fd, "r");
char *line = NULL;
size_t line_length;
getline(&line, &line_length, pipe);
```

Then use strchr to locate the :s in the line. (Don't be tempted to use strtok, it's only suitable for whitespace-separated fields that can't be empty.)

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