hello_ll.c File Reference

#include <fuse_lowlevel.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>

Go to the source code of this file.

Detailed Description

minimal example filesystem using low-level API

Compile with:

gcc -Wall hello_ll.c `pkg-config fuse3 --cflags --libs` -o hello_ll

Source code

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
*/

#define FUSE_USE_VERSION 31

#include <fuse_lowlevel.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>

static const char *hello_str = "Hello World!\n";
static const char *hello_name = "hello";

static int hello_stat(fuse_ino_t ino, struct stat *stbuf)
{
        stbuf->st_ino = ino;
        switch (ino) {
        case 1:
                stbuf->st_mode = S_IFDIR | 0755;
                stbuf->st_nlink = 2;
                break;

        case 2:
                stbuf->st_mode = S_IFREG | 0444;
                stbuf->st_nlink = 1;
                stbuf->st_size = strlen(hello_str);
                break;

        default:
                return -1;
        }
        return 0;
}

static void hello_ll_getattr(fuse_req_t req, fuse_ino_t ino,
                             struct fuse_file_info *fi)
{
        struct stat stbuf;

        (void) fi;

        memset(&stbuf, 0, sizeof(stbuf));
        if (hello_stat(ino, &stbuf) == -1)
                fuse_reply_err(req, ENOENT);
        else
                fuse_reply_attr(req, &stbuf, 1.0);
}

static void hello_ll_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
{
        struct fuse_entry_param e;

        if (parent != 1 || strcmp(name, hello_name) != 0)
                fuse_reply_err(req, ENOENT);
        else {
                memset(&e, 0, sizeof(e));
                e.ino = 2;
                e.attr_timeout = 1.0;
                e.entry_timeout = 1.0;
                hello_stat(e.ino, &e.attr);

                fuse_reply_entry(req, &e);
        }
}

struct dirbuf {
        char *p;
        size_t size;
};

static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
                       fuse_ino_t ino)
{
        struct stat stbuf;
        size_t oldsize = b->size;
        b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
        b->p = (char *) realloc(b->p, b->size);
        memset(&stbuf, 0, sizeof(stbuf));
        stbuf.st_ino = ino;
        fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
                          b->size);
}

#define min(x, y) ((x) < (y) ? (x) : (y))

static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
                             off_t off, size_t maxsize)
{
        if (off < bufsize)
                return fuse_reply_buf(req, buf + off,
                                      min(bufsize - off, maxsize));
        else
                return fuse_reply_buf(req, NULL, 0);
}

static void hello_ll_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
                             off_t off, struct fuse_file_info *fi)
{
        (void) fi;

        if (ino != 1)
                fuse_reply_err(req, ENOTDIR);
        else {
                struct dirbuf b;

                memset(&b, 0, sizeof(b));
                dirbuf_add(req, &b, ".", 1);
                dirbuf_add(req, &b, "..", 1);
                dirbuf_add(req, &b, hello_name, 2);
                reply_buf_limited(req, b.p, b.size, off, size);
                free(b.p);
        }
}

static void hello_ll_open(fuse_req_t req, fuse_ino_t ino,
                          struct fuse_file_info *fi)
{
        if (ino != 2)
                fuse_reply_err(req, EISDIR);
        else if ((fi->flags & 3) != O_RDONLY)
                fuse_reply_err(req, EACCES);
        else
                fuse_reply_open(req, fi);
}

static void hello_ll_read(fuse_req_t req, fuse_ino_t ino, size_t size,
                          off_t off, struct fuse_file_info *fi)
{
        (void) fi;

        assert(ino == 2);
        reply_buf_limited(req, hello_str, strlen(hello_str), off, size);
}

static struct fuse_lowlevel_ops hello_ll_oper = {
        .lookup         = hello_ll_lookup,
        .getattr        = hello_ll_getattr,
        .readdir        = hello_ll_readdir,
        .open           = hello_ll_open,
        .read           = hello_ll_read,
};

int main(int argc, char *argv[])
{
        struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
        struct fuse_session *se;
        struct fuse_cmdline_opts opts;
        int ret = -1;

        if (fuse_parse_cmdline(&args, &opts) != 0)
                return 1;
        if (opts.show_help) {
                printf("usage: %s [options] <mountpoint>\n\n", argv[0]);
                fuse_cmdline_help();
                fuse_lowlevel_help();
                ret = 0;
                goto err_out1;
        } else if (opts.show_version) {
                printf("FUSE library version %s\n", fuse_pkgversion());
                fuse_lowlevel_version();
                ret = 0;
                goto err_out1;
        }

        se = fuse_session_new(&args, &hello_ll_oper,
                              sizeof(hello_ll_oper), NULL);
        if (se == NULL)
            goto err_out1;

        if (fuse_set_signal_handlers(se) != 0)
            goto err_out2;

        if (fuse_session_mount(se, opts.mountpoint) != 0)
            goto err_out3;

        fuse_daemonize(opts.foreground);

        /* Block until ctrl+c or fusermount -u */
        if (opts.singlethread)
                ret = fuse_session_loop(se);
        else
                ret = fuse_session_loop_mt(se, opts.clone_fd);

        fuse_session_unmount(se);
err_out3:
        fuse_remove_signal_handlers(se);
err_out2:
        fuse_session_destroy(se);
err_out1:
        free(opts.mountpoint);
        fuse_opt_free_args(&args);

        return ret ? 1 : 0;
}

Definition in file hello_ll.c.