hello.c

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/*
  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.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <assert.h>

/*
 * Command line options
 *
 * We can't set default values for the char* fields here because
 * fuse_opt_parse would attempt to free() them when the user specifies
 * different values on the command line.
 */
static struct options {
        const char *filename;
        const char *contents;
        int show_help;
} options;

#define OPTION(t, p)                           \
    { t, offsetof(struct options, p), 1 }
static const struct fuse_opt option_spec[] = {
        OPTION("--name=%s", filename),
        OPTION("--contents=%s", contents),
        OPTION("-h", show_help),
        OPTION("--help", show_help),
        FUSE_OPT_END
};

static void *hello_init(struct fuse_conn_info *conn,
                        struct fuse_config *cfg)
{
        (void) conn;
        cfg->kernel_cache = 1;
        return NULL;
}

static int hello_getattr(const char *path, struct stat *stbuf,
                         struct fuse_file_info *fi)
{
        (void) fi;
        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+1, options.filename) == 0) {
                stbuf->st_mode = S_IFREG | 0444;
                stbuf->st_nlink = 1;
                stbuf->st_size = strlen(options.contents);
        } else
                res = -ENOENT;

        return res;
}

static int hello_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
                         off_t offset, struct fuse_file_info *fi,
                         enum fuse_readdir_flags flags)
{
        (void) offset;
        (void) fi;
        (void) flags;

        if (strcmp(path, "/") != 0)
                return -ENOENT;

        filler(buf, ".", NULL, 0, 0);
        filler(buf, "..", NULL, 0, 0);
        filler(buf, options.filename, NULL, 0, 0);

        return 0;
}

static int hello_open(const char *path, struct fuse_file_info *fi)
{
        if (strcmp(path+1, options.filename) != 0)
                return -ENOENT;

        if ((fi->flags & O_ACCMODE) != 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+1, options.filename) != 0)
                return -ENOENT;

        len = strlen(options.contents);
        if (offset < len) {
                if (offset + size > len)
                        size = len - offset;
                memcpy(buf, options.contents + offset, size);
        } else
                size = 0;

        return size;
}

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

static void show_help(const char *progname)
{
        printf("usage: %s [options] <mountpoint>\n\n", progname);
        printf("File-system specific options:\n"
               "    --name=<s>          Name of the \"hello\" file\n"
               "                        (default: \"hello\")\n"
               "    --contents=<s>      Contents \"hello\" file\n"
               "                        (default \"Hello, World!\\n\")\n"
               "\n");
}

int main(int argc, char *argv[])
{
        struct fuse_args args = FUSE_ARGS_INIT(argc, argv);

        /* Set defaults -- we have to use strdup so that
           fuse_opt_parse can free the defaults if other
           values are specified */
        options.filename = strdup("hello");
        options.contents = strdup("Hello World!\n");

        /* Parse options */
        if (fuse_opt_parse(&args, &options, option_spec, NULL) == -1)
                return 1;

        /* When --help is specified, first print our own file-system
           specific help text, then signal fuse_main to show
           additional help (by adding `--help` to the options again)
           without usage: line (by setting argv[0] to the empty
           string) */
        if (options.show_help) {
                show_help(argv[0]);
                assert(fuse_opt_add_arg(&args, "--help") == 0);
                args.argv[0] = (char*) "";
        }

        return fuse_main(args.argc, args.argv, &hello_oper, NULL);
}