计算目录中具有给定扩展名的文件数量 - C++?

发布于 2024-08-15 16:05:38 字数 278 浏览 2 评论 0原文

在 C++ 中是否可以计算目录中具有给定扩展名的文件的数量？

我正在编写一个程序，最好做这样的事情（伪代码）：

if (file_extension == ".foo")
    num_files++;
for (int i = 0; i < num_files; i++)
    // do something

显然，这个程序要复杂得多，但这应该让您大致了解我正在尝试做什么。

如果这是不可能的，请告诉我。

谢谢！

原文

Is it possible in c++ to count the number of files with a given extension in a directory?

I'm writing a program where it would be nice to do something like this (pseudo-code):

if (file_extension == ".foo")
    num_files++;
for (int i = 0; i < num_files; i++)
    // do something

Obviously, this program is much more complex, but this should give you the general idea of what I'm trying to do.

If this is not possible, just tell me.

Thanks!

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空城旧梦 2024-08-22 16:05:38

C 或 C++ 标准本身没有任何关于目录处理的内容，但几乎任何有价值的操作系统都会有这样的野兽，一个例子是 findfirst/findnext 函数或readdir。

您执行此操作的方法是对这些函数进行简单的循环，检查为您想要的扩展返回的字符串的末尾。

类似于：

char *fspec = findfirst("/tmp");
while (fspec != NULL) {
    int len = strlen (fspec);
    if (len >= 4) {
        if (strcmp (".foo", fspec + len - 4) == 0) {
            printf ("%s\n", fspec);
        }
    }
    fspec = findnext();
}

如上所述，您将用于遍历目录的实际函数是特定于操作系统的。

对于 UNIX，几乎肯定会使用 opendir，readdir 和 closedir。这段代码是一个很好的起点：

#include <dirent.h>

int len;
struct dirent *pDirent;
DIR *pDir;

pDir = opendir("/tmp");
if (pDir != NULL) {
    while ((pDirent = readdir(pDir)) != NULL) {
        len = strlen (pDirent->d_name);
        if (len >= 4) {
            if (strcmp (".foo", &(pDirent->d_name[len - 4])) == 0) {
                printf ("%s\n", pDirent->d_name);
            }
        }
    }
    closedir (pDir);
}

There is nothing in the C or C++ standards themselves about directory handling but just about any OS worth its salt will have such a beast, one example being the findfirst/findnext functions or readdir.

The way you would do it is a simple loop over those functions, checking the end of the strings returned for the extension you want.

Something like:

char *fspec = findfirst("/tmp");
while (fspec != NULL) {
    int len = strlen (fspec);
    if (len >= 4) {
        if (strcmp (".foo", fspec + len - 4) == 0) {
            printf ("%s\n", fspec);
        }
    }
    fspec = findnext();
}

As stated, the actual functions you will use for traversing the directory are OS-specific.

For UNIX, it would almost certainly be the use of opendir, readdir and closedir. This code is a good starting point for that:

#include <dirent.h>

int len;
struct dirent *pDirent;
DIR *pDir;

pDir = opendir("/tmp");
if (pDir != NULL) {
    while ((pDirent = readdir(pDir)) != NULL) {
        len = strlen (pDirent->d_name);
        if (len >= 4) {
            if (strcmp (".foo", &(pDirent->d_name[len - 4])) == 0) {
                printf ("%s\n", pDirent->d_name);
            }
        }
    }
    closedir (pDir);
}

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