使用nftw()（File Tree Walk）函数，带有FTW_DEPTH标志。提供一个回调函数，只对传递的文件调用remove()：

#define _XOPEN_SOURCE 500
#include <stdio.h>
#include <ftw.h>
#include <unistd.h>

int unlink_cb(const char *fpath, const struct stat *sb, int typeflag, struct FTW *ftwbuf)
{
    int rv = remove(fpath);

    if (rv)
        perror(fpath);

    return rv;
}

int rmrf(char *path)
{
    return nftw(path, unlink_cb, 64, FTW_DEPTH | FTW_PHYS);
}

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1.您需要使用nftw()（也可能是ftw()）来遍历层次结构。
1.您需要使用unlink()删除文件和其他非目录。
1.您需要使用rmdir()删除（空）目录。
你最好使用nftw()（而不是ftw()），因为它提供了像FTW_DEPTH这样的控件，可以确保在访问目录本身之前访问目录下的所有文件。

您可以在纯C语言上编写自己的实现命令**“rm -rf”。源代码仅基于头文件：direent.h、sys/stat.h和unistd.h**。如果您需要将代码移植到其他系统，例如Windows，您只需更改具有相应功能的头文件，同时算法不会更改。
一个文件rmtree.c

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

// POSIX dependencies
#include <dirent.h>
#include <sys/stat.h>
#include <unistd.h>

void
rmtree(const char path[])
{
    size_t path_len;
    char *full_path;
    DIR *dir;
    struct stat stat_path, stat_entry;
    struct dirent *entry;

    // stat for the path
    stat(path, &stat_path);

    // if path does not exists or is not dir - exit with status -1
    if (S_ISDIR(stat_path.st_mode) == 0) {
        fprintf(stderr, "%s: %s\n", "Is not directory", path);
        exit(-1);
    }

    // if not possible to read the directory for this user
    if ((dir = opendir(path)) == NULL) {
        fprintf(stderr, "%s: %s\n", "Can`t open directory", path);
        exit(-1);
    }

    // the length of the path
    path_len = strlen(path);

    // iteration through entries in the directory
    while ((entry = readdir(dir)) != NULL) {

        // skip entries "." and ".."
        if (!strcmp(entry->d_name, ".") || !strcmp(entry->d_name, ".."))
            continue;

        // determinate a full path of an entry
        full_path = calloc(path_len + 1 + strlen(entry->d_name) + 1, sizeof(char));
        strcpy(full_path, path);
        strcat(full_path, "/");
        strcat(full_path, entry->d_name);

        // stat for the entry
        stat(full_path, &stat_entry);

        // recursively remove a nested directory
        if (S_ISDIR(stat_entry.st_mode) != 0) {
            rmtree(full_path);
            free(full_path);
            continue;
        }

        // remove a file object
        if (unlink(full_path) == 0)
            printf("Removed a file:\t%s\n", full_path);
        else
            printf("Can't remove a file:\t%s\n", full_path);
        free(full_path);
    }

    // remove the devastated directory and close the object of it
    if (rmdir(path) == 0)
        printf("Removed a directory:\t%s\n", path);
    else
        printf("Can't remove a directory:\t%s\n", path);

    closedir(dir);
}

int
main(const int argc, char const *argv[])
{
    if (argc != 2) {
        fprintf(stderr, "Missing single operand: path\n");
        return -1;
    }

    rmtree(argv[1]);

    return 0;
}

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查看。

我正在使用shell脚本生成文件/文件夹结构。

$ cat script.sh 

mkdir -p dir1/{dir1.1,dir1.2,dir1.3}
mkdir -p dir1/dir1.2/{dir1.2.1,dir1.2.2,dir1.2.3}
mkdir -p dir2/{dir2.1,dir2.2}
mkdir -p dir2/dir2.2/dir2.2.1
mkdir -p dir2/dir2.2/{dir2.2.1,dir2.2.2}
mkdir -p dir3/dir3.1
mkdir -p dir4
mkdir -p dir5

touch dir1/dir1.1/file.scala
touch dir1/dir1.2/file.scala
touch dir2/dir2.2/{file.c,file.cpp}
touch dir2/dir2.2/dir2.2.2/{file.go,file.rb}
touch dir3/{file.js,file.java}
touch dir3/dir3.1/{file.c,file.cpp}
> dir4/file.py

型
运行脚本

$ ./script.sh

型
生成文件/文件夹结构

$ tree
.
├── dir1
│   ├── dir1.1
│   │   └── file.scala
│   ├── dir1.2
│   │   ├── dir1.2.1
│   │   ├── dir1.2.2
│   │   ├── dir1.2.3
│   │   └── file.scala
│   └── dir1.3
├── dir2
│   ├── dir2.1
│   └── dir2.2
│       ├── dir2.2.1
│       ├── dir2.2.2
│       │   ├── file.go
│       │   └── file.rb
│       ├── file.c
│       └── file.cpp
├── dir3
│   ├── dir3.1
│   │   ├── file.c
│   │   └── file.cpp
│   ├── file.java
│   └── file.js
├── dir4
│   └── file.py
├── dir5
├── rmtree.c
└── script.sh

16 directories, 13 files

型
通过GCC构建文件rmtree. c的源代码

$ cc -o -Wall -Werror -o rmtree rmtree.c

型
删除目录dir 1/dir1.1

$ ./rmtree dir1/dir1.1
Removed a file:         dir1/dir1.1/file.scala
Removed a directory:    dir1/dir1.1

型
删除目录dir 1/dir1.2

$ ./rmtree dir1/dir1.2
Removed a directory:    dir1/dir1.2/dir1.2.3
Removed a file:         dir1/dir1.2/file.scala
Removed a directory:    dir1/dir1.2/dir1.2.1
Removed a directory:    dir1/dir1.2/dir1.2.2
Removed a directory:    dir1/dir1.2

型
删除目录dir 1/

$ ./rmtree dir1
Removed a directory:    dir1/dir1.3
Removed a directory:    dir1

型
删除目录dir 2/dir2.2/dir2.2.2

$ ./rmtree dir2/dir2.2/dir2.2.2
Removed a file:         dir2/dir2.2/dir2.2.2/file.rb
Removed a file:         dir2/dir2.2/dir2.2.2/file.go
Removed a directory:    dir2/dir2.2/dir2.2.2

型
删除目录dir 2/

$ ./rmtree dir2
Removed a directory:    dir2/dir2.1
Removed a file:         dir2/dir2.2/file.c
Removed a directory:    dir2/dir2.2/dir2.2.1
Removed a file:         dir2/dir2.2/file.cpp
Removed a directory:    dir2/dir2.2
Removed a directory:    dir2

型
删除目录dir 3/dir3.1

$ ./rmtree dir3/dir3.1
Removed a file:         dir3/dir3.1/file.c
Removed a file:         dir3/dir3.1/file.cpp
Removed a directory:    dir3/dir3.1

型
删除目录dir 3

$ ./rmtree dir3
Removed a file:         dir3/file.js
Removed a file:         dir3/file.java
Removed a directory:    dir3

型
删除目录dir 4

$ ./rmtree dir4
Removed a file:         dir4/file.py
Removed a directory:    dir4

型
删除空目录dir 5

$ ./rmtree dir5
Removed a directory:    dir5

如果传递的路径不存在或不是目录的路径，您将看到下一个：

$ ./rmtree rmtree.c
Is not directory: rmtree.c
$ ./rmtree 11111111111111111
Is not directory: 11111111111111111

查看结果

$ tree
.
├── rmtree
├── rmtree.c
└── script.sh

0 directories, 3 files

测试环境

$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux 8.7 (jessie)
Release:    8.7
Codename:   jessie
$ uname -a
Linux localhost 3.16.0-4-amd64 #1 SMP Debian 3.16.36-1+deb8u2 (2016-10-19) x86_64 GNU/Linux
$ cc --version
cc (Debian 4.9.2-10) 4.9.2

我刚刚破解了GNU rm源代码，看看它到底是做什么的：
http://www.gnu.org/software/coreutils/
rm依靠以下职能：

fts_open
fts_read
fts_set
fts_close

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在Linux和Mac上都有手册页。

请参阅man 2 unlink和man 2 rmdir，了解将分别删除文件和（空）目录的系统调用。为了处理递归情况，您需要做的就是以后序深度优先遍历目标目录，并使用正确的删除例程按该顺序删除每个条目。您可以使用opendir，readdir，和closedir来遍历目录结构。

在伪代码中，下面是我将采用的非递归方法：

create a stack to hold directory names.
push argv contents onto the stack
while (stack !empty) {
    look at the top directory name on the stack
    for each item in directory {
        if (item is a directoy) {
            push it onto the stack
        } else {
            delete it
        }
    }
    if (no subdirs were pushed) {
        pop the top dir name from the stack
        delete it
    }
}

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我将把在C中实现这个作为读者的练习。
(Edit：此外，除非这纯粹是一个学习练习，否则不要重新发明这个轮子--像其他人建议的那样使用ftw或nftw会容易得多，因此不太容易出错。）