getopt_long（） - 有道使用它？ [英] getopt_long() -- proper way to use it?

问题描述

OK，我已搜查，发现我开始在正确的方向以下两个StackOverflow的主题：

OK, I have searched and found the following two StackOverflow topics that started me in the right direction:

<一个href=\"http://stackoverflow.com/questions/189972/argument-parsing-helpers-for-c-unix/\">Argument-parsing对于C / UNIX 佣工

<一个href=\"http://stackoverflow.com/questions/498320/pass-arguments-into-c-program-from-command-line\">Pass参数到C程序的命令行

注：所有code是伪code。会后编译code工作时。

NOTE: ALL CODE IS PSEUDO-CODE. WILL POST COMPILABLE CODE WHEN IT WORKS.

不过，我还是如何在C.将getopt_long（）我写的程序被定义为具有以下可能的标签（但可以包含多达你绝对需要，填补剩下的完全糊涂空值）：

However, I'm still completely confused on how to use getopt_long() in C. The program I'm writing is defined as having the following possible tags (but can include as many as you absolutely need, filling the rest in with empty values):

id3tagEd filename -title "title" -artist "artist" -year 1991 -comment "comment" -album "album" -track 1

现在，从我读，我需要利用结构为长选项，正确吗？如果是这样，我写的东西沿着这行：

Now, from what I read, I need to utilize a struct for the long options, correct? If so, I wrote something along the lines of this:

struct fields field =
{
    char *[] title;
    char *[] artist;
    char *[] album;
    int year;
    char *[] comment;
    int track;
}


static struct options long_options[] =
{
    {"title", 0, &field.title, 't'},
    {"artist", 0, &field.artist, 'a'},
    {"album", 0, &field.album, 'b'},
    {"year", 0, &field.year, 'y'},
    {"comment", 0, &field.comment, 'c'},
    {"track", 0, &field.track, 'u'},
    {0, 0, 0, 0}
}

现在，从我收集的，我会通过此调用它：

Now, from what I gathered, I would be calling it via this:

int option_index = 0;

int values = getopt_long(argc, argv, "tabycu", long_options, &option_index);

从这里，我可以用严格的现场结构，做什么，我需要我的计划之内？但是，如果是这种情况，有人可以解释整个long_options结构？我读了手册页和这样的，我只是心乱如麻。通过重读手册页，我可以看到我可以给变量设置为null，和我所有的选择需求应该被设置为required_argument？然后，通过一个while（）循环设置结构？但是，我看到OPTARG被使用。这组由getopt_long（）？抑或是从这个例子里缺？

From here, could I strictly use the field struct and do what I need to within my program? However, if this is the case, can someone explain the whole long_options struct? I read the man pages and such, and I'm just utterly confused. By rereading the man pages, I can see I can set variables to null, and should be setting all my option requirements to "required_argument"? And then setting the structs via a while() loop? However, I see optarg being used. Is this set by getopt_long()? Or is it missing from the example?

和最后一个问题，我总会有一位不愿透露姓名的必需选项：文件名，将我只是用的argv [0]来访问呢？ （因为我可以假设它会是第一个）。

And one last issue, I will always have an unnamed required option: filename, would I just use argv[0] to gain access to that? (Since I can assume it'll be first).

在一个侧面说明，这是关系到一个家庭作业的问题，但它没有任何关系确定其更多的是基本的它，必须了解的参数传递，并通过命令行先用C解析。

On a side note, this is related to a homework problem, but it has nothing to do with fixing it, its more of a fundamental, have to understand argument passing and parsing in C via command line first.

推荐答案

首先，你可能不希望 0 为 has_​​arg 领域 - 它必须是 no_argument ， required_arguemnt 或 optional_argument 。在你的情况，所有的人都将是 required_argument 。除此之外，你不使用标志字段正确的 - 它必须是整数指针。如果相应的标志设置， getopt_long（）将与您通过 VAL 字段传递的整数填入。我不认为你需要在所有此功能。这里有一个更好的（缩短）例如，对于您的情况：

First off, you probably don't want 0 for the has_arg field - it must be one of no_argument, required_arguemnt, or optional_argument. In your case, all of them are going to be required_argument. Besides that, you're not using the flag field correctly - it has to be an integer pointer. If the corresponding flag is set, getopt_long() will fill it in with the integer you passed in via the val field. I don't think you need this feature at all. Here's a better (shortened) example for your case:

static struct option long_options[] =
{
    {"title", required_argument, NULL, 't'},
    {"artist", required_argument, NULL, 'a'},
    {NULL, 0, NULL, 0}
};

后来的后来，你可以适当地使用它（直接从手册页，我添加了一些注释）：

Then later, you can use it appropriately (straight from the manpage, I added some comments):

// loop over all of the options
while ((ch = getopt_long(argc, argv, "t:a:", long_options, NULL)) != -1)
{
    // check to see if a single character or long option came through
    switch (ch)
    {
         // short option 't'
         case 't':
             field.title = optarg; // or copy it if you want to
             break;
         // short option 'a'
         case 'a':
             field.artist = optarg; // or copy it if you want to
             break;
    }
}

您可以为您的其他领域扩展必要的（并添加一些错误处理，拜托了！）。注 - 如果你想使用 -title 和 -artist 就像你在你的例子有，你需要使用 getopt_long_only（），它没有短选项。

You can extend for your other fields as necessary (and add some error handling, please!). Note - if you want to use -title and -artist like you have in your example, you'll need to use getopt_long_only(), which doesn't have short options.

至于你的文件名选项，你会得到作为一个？从 getopt_long（）电话，所以你可以在那个时候处理。的其他选项是，要求它是第一或者最后的选项，并通过它本身单独处理。

As to your filename option, you'll get that out as a '?' from the getopt_long() call, so you could handle it at that time. Your other options are to require that it is either the first or the last option and handle it by itself separately.

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