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 GPLv2.
 * 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;
 
        /* Test setting flags the old way */
        conn->want = FUSE_CAP_ASYNC_READ;
        conn->want &= ~FUSE_CAP_ASYNC_READ;
 
        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, FUSE_FILL_DIR_DEFAULTS);
        filler(buf, "..", NULL, 0, FUSE_FILL_DIR_DEFAULTS);
        filler(buf, options.filename, NULL, 0, FUSE_FILL_DIR_DEFAULTS);
 
        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 const 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[])
{
        int ret;
        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][0] = '\0';
        }
 
        ret = fuse_main(args.argc, args.argv, &hello_oper, NULL);
        fuse_opt_free_args(&args);
        return ret;
}