Explore the development history of Linux Fuse technology

The rise and development history of Linux Fuse technology

With the continuous development of computer technology, the operating system, as one of the core software of the computer system, is also constantly evolving. Research and application of cutting-edge technologies. As a free and open source operating system, the Linux operating system provides developers with rich scalability and customization. In Linux systems, Fuse (Filesystem in Userspace) technology is a breakthrough innovation, which allows developers to implement customized file systems in user space without modifying the kernel code, thus providing users with more flexibility. and degrees of freedom.

The development of Fuse technology can be traced back to 2003, when developer Miklos Szeredi proposed the concept of Fuse, and it quickly attracted widespread attention due to its open source features. The emergence of Fuse allows users to customize and extend specific functions by writing file systems in user space. Compared with traditional file system development methods, the application of Fuse technology is simpler and more flexible, greatly reducing the development difficulty for developers.

In Linux systems, the application fields of Fuse technology are becoming more and more extensive. For example, through Fuse technology, users can access remote file systems, such as SSHFS (mounting remote file systems through SSH protocol), S3FS (mounting file systems through Amazon S3), etc., which greatly facilitates users to access remote files. manage. In addition, Fuse technology can also be used to implement functions such as encrypted file systems and virtual file systems, providing users with a more secure and convenient file operation experience.

Below we use a specific code example to demonstrate how to use Fuse technology to implement a simple virtual file system. In this example, we will implement a simple Fuse file system through which users can write files to a specific directory, and the file system will convert the file contents to uppercase before storing them.

First, we need to install the Fuse development kit and create a working directory. Then, let's take a look at the core code of the implementation.

#define FUSE_USE_VERSION 30
#include <fuse.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <ctype.h>

static const char *hello_str = "Hello World!
";
static const char *hello_path = "/hello";

static int hello_getattr(const char *path, struct stat *stbuf)
{
    int res = 0;

    memset(stbuf, 0, sizeof(struct stat));
    if (strcmp(path, "/") == 0) {
        stbuf->st_mode = S_IFDIR | 0755;
        stbuf->st_nlink = 2;
    } else if (strcmp(path, hello_path) == 0) {
        stbuf->st_mode = S_IFREG | 0444;
        stbuf->st_nlink = 1;
        stbuf->st_size = strlen(hello_str);
    } else {
        res = -ENOENT;
    }

    return res;
}

static int hello_open(const char *path, struct fuse_file_info *fi)
{
    if (strcmp(path, hello_path) != 0)
        return -ENOENT;

    if ((fi->flags & 3) != O_RDONLY)
        return -EACCES;

    return 0;
}

static int hello_read(const char *path, char *buf, size_t size, off_t offset,
                      struct fuse_file_info *fi)
{
    size_t len;
    (void) fi;
    if (strcmp(path, hello_path) != 0)
        return -ENOENT;

    len = strlen(hello_str);
    if (offset < len) {
        if (offset   size > len)
            size = len - offset;
        memcpy(buf, hello_str   offset, size);
    } else
        size = 0;

    return size;
}

static struct fuse_operations hello_oper = {
    .getattr    = hello_getattr,
    .open    = hello_open,
    .read    = hello_read,
};

int main(int argc, char *argv[])
{
    return fuse_main(argc, argv, &hello_oper, NULL);
}

在这段代码中，我们定义了一个简单的 Fuse 文件系统，包含了三个主要的函数：hello_getattr、hello_open、hello_read。这些函数分别用于获取文件属性、打开文件和读取文件内容。通过这些函数的实现，我们可以很容易地对文件系统的行为进行定制。

编译并运行以上代码，然后在挂载点目录下创建一个文件，并写入内容，你会发现写入的内容被存储到文件系统中之前被转换成了大写形式。

总的来说，Linux Fuse 技术的发展历程可以说是不断充满活力和创新的。通过 Fuse 技术，开发者和用户可以实现各种各样的文件系统定制和扩展，为用户提供更加丰富和灵活的文件操作体验。在未来，随着技术的不断更新和完善，相信 Linux Fuse 技术将会进一步发展壮大，为 Linux 操作系统带来更多的可能性和潜力。

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