c - 在 c 中使用 ntfw 时跳过子目录

Question

我正在尝试使用 nftw 获取当前或提到的文件夹中的所有文件和目录.但是我如何指示函数不要在任何子目录中走得更远呢？标记 FTW_SKIP_SUBTREE 的用途是什么？还有这个常量的头文件是什么。

#include <ftw.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

static int
display_info(const char *fpath, const struct stat *sb,
             int tflag, struct FTW *ftwbuf)
{

    printf("%-3s %2d %7jd   %-40s %d %s\n",
        (tflag == FTW_D) ?   "d"   : (tflag == FTW_DNR) ? "dnr" :
        (tflag == FTW_DP) ?  "dp"  : (tflag == FTW_F) ?   "f" :
        (tflag == FTW_NS) ?  "ns"  : (tflag == FTW_SL) ?  "sl" :
        (tflag == FTW_SLN) ? "sln" : "???",
        ftwbuf->level, (intmax_t) sb->st_size,
        fpath, ftwbuf->base, fpath + ftwbuf->base);
    return 0;           /* To tell nftw() to continue */
}

int
main(int argc, char *argv[])
{
    int flags = 0;

    if (argc > 2 && strchr(argv[2], 'd') != NULL)
      flags |= FTW_DEPTH;
    if (argc > 2 && strchr(argv[2], 'p') != NULL)
      flags |= FTW_PHYS;
    if (argc > 2 && strchr(argv[2], 's') != NULL)
      flags |= FTW_SKIP_SUBTREE;

    if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags)
            == -1) {
        perror("nftw");
        exit(EXIT_FAILURE);
    }
    exit(EXIT_SUCCESS);
}

当我尝试编译时，我收到这条消息

test.c:33:16: error: ‘FTW_SKIP_SUBTREE’ undeclared (first use in this function)
       flags |= FTW_SKIP_SUBTREE;

Answer 1

nftw() 的手册页在 Linux 上说(部分):

nftw()

The function nftw() is the same as ftw(), except that it has one additional argument, flags, and calls fn() with one more argument, ftwbuf.

This flags argument is formed by ORing zero or more of the following flags:

• FTW_ACTIONRETVAL (since glibc 2.3.3)
  If this glibc-specific flag is set, then nftw() handles the return value from fn() differently. fn() should return one of the following values:

  • FTW_CONTINUE Instructs nftw() to continue normally.

  • FTW_SKIP_SIBLINGS
    If fn() returns this value, then siblings of the current entry will be skipped, and processing continues in the parent.

  • FTW_SKIP_SUBTREE
    If fn() is called with an entry that is a directory (typeflag is FTW_D), this return value will prevent objects within that directory from being passed as arguments to fn(). nftw() continues processing with the next sibling of the directory.

  • FTW_STOP
    Causes nftw() to return immediately with the return value FTW_STOP.

  • Other return values could be associated with new actions in the future; fn() should not return values other than those listed above.

  The feature test macro _GNU_SOURCE must be defined in order to obtain the definition of FTW_ACTIONRETVAL from <ftw.h>.

最后一段是您要注意的关键一段。