1 /*
2 FUSE: Filesystem in Userspace
3 Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
4
5 This program can be distributed under the terms of the GNU GPLv2.
6 See the file COPYING.
7 */
8
9 /** @file
10 *
11 * This "filesystem" provides only a single file. The mountpoint
12 * needs to be a file rather than a directory. All writes to the
13 * file will be discarded, and reading the file always returns
14 * \0.
15 *
16 * Compile with:
17 *
18 * gcc -Wall null.c `pkg-config fuse3 --cflags --libs` -o null
19 *
20 * ## Source code ##
21 * \include passthrough_fh.c
22 */
23
24
25 #define FUSE_USE_VERSION 31
26
27 #include <fuse.h>
28 #include <fuse_lowlevel.h>
29 #include <stdio.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #include <unistd.h>
33 #include <time.h>
34 #include <errno.h>
35
null_getattr(const char * path,struct stat * stbuf,struct fuse_file_info * fi)36 static int null_getattr(const char *path, struct stat *stbuf,
37 struct fuse_file_info *fi)
38 {
39 (void) fi;
40
41 if(strcmp(path, "/") != 0)
42 return -ENOENT;
43
44 stbuf->st_mode = S_IFREG | 0644;
45 stbuf->st_nlink = 1;
46 stbuf->st_uid = getuid();
47 stbuf->st_gid = getgid();
48 stbuf->st_size = (1ULL << 32); /* 4G */
49 stbuf->st_blocks = 0;
50 stbuf->st_atime = stbuf->st_mtime = stbuf->st_ctime = time(NULL);
51
52 return 0;
53 }
54
null_truncate(const char * path,off_t size,struct fuse_file_info * fi)55 static int null_truncate(const char *path, off_t size,
56 struct fuse_file_info *fi)
57 {
58 (void) size;
59 (void) fi;
60
61 if(strcmp(path, "/") != 0)
62 return -ENOENT;
63
64 return 0;
65 }
66
null_open(const char * path,struct fuse_file_info * fi)67 static int null_open(const char *path, struct fuse_file_info *fi)
68 {
69 (void) fi;
70
71 if(strcmp(path, "/") != 0)
72 return -ENOENT;
73
74 return 0;
75 }
76
null_read(const char * path,char * buf,size_t size,off_t offset,struct fuse_file_info * fi)77 static int null_read(const char *path, char *buf, size_t size,
78 off_t offset, struct fuse_file_info *fi)
79 {
80 (void) buf;
81 (void) offset;
82 (void) fi;
83
84 if(strcmp(path, "/") != 0)
85 return -ENOENT;
86
87 if (offset >= (1ULL << 32))
88 return 0;
89
90 memset(buf, 0, size);
91 return size;
92 }
93
null_write(const char * path,const char * buf,size_t size,off_t offset,struct fuse_file_info * fi)94 static int null_write(const char *path, const char *buf, size_t size,
95 off_t offset, struct fuse_file_info *fi)
96 {
97 (void) buf;
98 (void) offset;
99 (void) fi;
100
101 if(strcmp(path, "/") != 0)
102 return -ENOENT;
103
104 return size;
105 }
106
107 static const struct fuse_operations null_oper = {
108 .getattr = null_getattr,
109 .truncate = null_truncate,
110 .open = null_open,
111 .read = null_read,
112 .write = null_write,
113 };
114
main(int argc,char * argv[])115 int main(int argc, char *argv[])
116 {
117 struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
118 struct fuse_cmdline_opts opts;
119 struct stat stbuf;
120
121 if (fuse_parse_cmdline(&args, &opts) != 0)
122 return 1;
123 fuse_opt_free_args(&args);
124
125 if (!opts.mountpoint) {
126 fprintf(stderr, "missing mountpoint parameter\n");
127 return 1;
128 }
129
130 if (stat(opts.mountpoint, &stbuf) == -1) {
131 fprintf(stderr ,"failed to access mountpoint %s: %s\n",
132 opts.mountpoint, strerror(errno));
133 free(opts.mountpoint);
134 return 1;
135 }
136 free(opts.mountpoint);
137 if (!S_ISREG(stbuf.st_mode)) {
138 fprintf(stderr, "mountpoint is not a regular file\n");
139 return 1;
140 }
141
142 return fuse_main(argc, argv, &null_oper, NULL);
143 }
144