c++ - 如何在C++中检查char数组是否包含任何不带循环的char？

Question

我正在使用opendir和readdir函数在给定目录中搜​​索包含.txt的文件名。

有什么方法可以通过函数而不使用循环来测试certain extension？ (当前，我必须遍历de-> d_filename进行检查，但它们相当复杂，此外，我尝试了de->d_type，但未返回扩展名)

另外，此函数返回文件名的名称，我想要的结果是从头开始获取路径名，是否存在类似于de->d_fullfilepath?的函数返回wchar_t *

这就是我所拥有的:

DIR* dr = opendir(lpszFolder);
vector<const wchar_t*> names;  //get list file with extension .txt then push to this vector

if (dr == NULL)  // opendir returns NULL if couldn't open directory 
{
    printf("Could not open current directory");
    return {};
}

// Refer http://pubs.opengroup.org/onlinepubs/7990989775/xsh/readdir.html 
// for readdir() 
while ((de = readdir(dr)) != NULL)
{
    if (de->d_type ... 'txt') // function get just .txt file.
    {
        wchar_t* pwc =new wchar_t(lpszFolder);       //initialize new instance file path
        const size_t cSize = de->d_namlen + 1;       //get file len
        mbstowcs(pwc, de->d_name, cSize);            //combine thisfilepath + extension
        names.push_back(pwc);
    }
}

Answer 1

最佳Libc功能可反向搜索

您可能会考虑strrchr

Locate last occurrence of character in string Returns a pointer to the last occurrence of character in the C string str.
The terminating null-character is considered part of the C string. Therefore, it can also be located to retrieve a pointer to the end of a string.

示例程序以查找具有特定文件扩展名的文件

#include <string.h>
#include <sys/types.h>
#include <dirent.h>
#include <string>
#include <vector>

using namespace std;

const char *get_filename_ext(const char *filename) {
    const char *dot = strrchr(filename, '.');
    return (!dot || dot == filename) ? "" : dot + 1;
}

int main(int ac, char **av) {
    if (ac != 2)
        return 1;
    const char *lookup = (ac==3) ? av[2] : "txt";

    const char *lpszFolder = av[1];
    DIR* dr = opendir(lpszFolder);
    vector<const wchar_t*> names;  //get list file with extension .txt then push     to this vector

    if (dr == NULL)  // opendir returns NULL if couldn't open directory 
    {
        printf("Could not open current directory");
        return (1);
    }
    struct dirent *ent;
    uint32_t len = sizeof(((dirent*)0)->d_name);
    char ext[len];
    while ((ent = readdir (dr)) != NULL) {
        (void)ext;
        strncpy(ext, get_filename_ext(ent->d_name), len-1);
        if (!strcmp(lookup, ext))
            names.push_back(reinterpret_cast < wchar_t*>(ent->d_name));
    }

    closedir(dr);

    for (auto name : names)
        printf("%s", (char *)name);
    return 0;
}

主要用途

测试:

g++ a.cpp && ./a.out myfolder

将查找所有扩展名为“.txt”的文件

或者，如果您想要像☠这样的特定扩展名:

g++ a.cpp && ./a.out myfolder ☠