在 C 中接受带有通配符的文件名的跨平台“标准”方式？

Question

I'm writing a command line utility in C to process image files. In its current state, the application can accept multiple explicit file names though argv , but I'd like to add support for wildcards, like this:

imgprocess.exe *.png *.gif

or

./imgprocess *.png *.gif

It seems like this should be a common enough thing to be supported by C99, but I'm having a very difficult time finding a standard, cross-platform solution.

For Windows, it appears (via this article ) that linking to setargv.obj does the trick, but that's specific to Windows and I think Visual Studio.

For Linux, it looks like readdir() or scandir() can get me a directory listing and I can iterate through that to match files, but I think that's just Linux.

Since wildcards are such a common thing, I feel like I'm missing some kind of simple obvious solution. Currently I'm on Linux compiling with gcc, but I would like it to compile for at least Windows and Linux.

Thank you for any advice.

Answer 1

On Linux-like systems at least, the shell expands the wildcard into a list of filenames. So there is no need to add this functionality!

Answer 2

The normal way to handle this problem in a UNIX or UNIX-like environment is to not handle it at all. That is, let the shell do the glob expansion. Your program just gets a big list of files and doesn't have to worry about looking around in the filesystem at all. A quick example program:

#include <stdio.h>

int main(int argc, char **argv)
{
  int i;

  for (i = 1; i < argc; i++)
  {
    printf("%s\n", argv[i]);
  }

  return 0;
}

And a couple of sample runs (the only files in the directory are example and example.c ):

$ ./example 
$ ./example *
example
example.c
$ ./example *.c
example.c

Answer 3

POSIX systems do support glob and globfree functions (try man 3 glob , becuase just man glob may get you the shell documentation) which do the same thing as the shell's glob behavior.

However--as others have said--it is not really common or expected that your program will process arguments that way: the user will have to quote the arguments to get them to you from the commend line.

---

If you want to be really cross-platform you may want to implement this functionality yourself. Say using PCRE (the Perl Compatible Regular Expression library) as the basis since this is available on all common platforms.