处理命令行参数？ [英] Handle command line arguments?

问题描述

因此，我可以使程序全部运行，但是如果得到提示

So, I can make my program run and all, but if I'm given

$ ./a.out -f Text.txt

我只是不确定如何获取程序来建立连接-f表示文件。这样做的逻辑是什么？

I'm just not sure how to get the program to make the connection that -f indicates a file. What is the logic for doing this?

推荐答案

main 函数具有签名 int main（int argc，char ** argv）;因此您可以使用 argc （是肯定的）& argv 参数。 argv 数组保证具有 argc + 1 元素。最后一个总是 NULL 。其他是非零，非混淆的零字节终止字符串。请注意，通常 shell 是浏览程序中的参数之前， execve（2）：参见 glob（7）。

The main function has signature int main(int argc, char**argv); so you can use the argc (which is positive) & argv arguments. The argv array is guaranteed to have argc+1 elements. The last is always NULL. The others are non-nil, non-aliased zero-byte terminated strings. Notice that often some shell is globbing the arguments before your program is started by execve(2): see glob(7).

例如，如果您键入（在Linux终端中） myprog -ia *。 c -o foo.txt ，并且如果您现在输入该外壳已扩展（通过通气）将 a * .c 转换为 a1.c 和 a2.c （因为这是仅有的名称以 a 开头且具有 .c 后缀（在当前目录中），您的 myprog 可执行文件 main 程序将被调用

For example, if you type (in a Linux terminal) myprog -i a*.c -o foo.txt and if at the moment you type that the shell has expanded (by globbing) a*.c into a1.c and a2.c (because these are the only files whose name start with a and have a .c suffix in the current directory), your myprog executable main program is called with

• argc == 6


• argv [0] 包含 myprog （因此您可以测试一下 strcmp（argv [0]， myprog）== 0 ）


• argv [1] 包含-i


• argv [2] 包含 a1.c


• argv [3] a2.c


• argv [4] 包含-o


• argv [5] 包含 foo.txt c>


• argv [6] 为 NULL 指针

• argc==6
• argv[0] containing "myprog" (so you could test that strcmp(argv[0],"myprog") == 0)
• argv[1] containing "-i"
• argv[2] containing "a1.c"
• argv[3] containing "a2.c"
• argv[4] containing "-o"
• argv[5] containing "foo.txt"
• argv[6] being the NULL pointer

此外，您可以保证（内核执行 execve（2））表示所有6个 argv 指针是不同的，非别名，并且不重叠。

In addition you are guaranteed (by the kernel doing the execve(2)) that all the 6 argv pointers are distinct, non-aliasing, and non-overlapping.

GNU libc为您提供几种方法来解析这些参数： getopt & argp 。 getopt 在POSIX中是标准化的（但是GNU也为您提供了非常有用的< a href = http://man7.org/linux/man-pages/man3/getopt.3.html rel = nofollow> getopt_long（3））

GNU libc gives you several ways to parse these arguments: getopt & argp. getopt is standardized in POSIX (but GNU gives you also the very useful getopt_long(3))

我强烈建议您遵循 GNU约定：至少接受-help 和-version

I strongly suggest you to follow GNU conventions: accept at least --help and --version

例如 -f 是用于某些选项的，并非通常使用文件名（但请参见程序参数中使用- ）。如果您碰巧真的想要一个名为 -f 的文件（这是一个非常糟糕的主意），请使用。/- f

The fact that e.g. -f is for some option and not a file name is often conventional (but see use of -- in program arguments). If you happen to really want a file named -f (which is a very bad idea), use ./-f

多个外壳具有自动补全。您需要为此配置它们（甚至可能为您自己的程序配置它们）。

Several shells have autocompletion. You need to configure them for that (and you might configure them even for your own programs).

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