Similar to stat(). The `st_dev` and `st_blksize` fields are ignored. The `st_ino` field is ignored except if the 'use_ino' mount option is given. In that case it is passed to userspace, but libfuse and the kernel will still assign a different inode for internal use (called the "nodeid").
`fi` will always be NULL if the file is not currenly open, but may also be NULL if the file is open.
int (*getattr) (const char *, struct stat *, struct fuse_file_info *fi);
##Read the target of a symbolic link The buffer should be filled with a null terminated string. The buffer size argument includes the space for the terminating null character. If the linkname is too long to fit in the buffer, it should be truncated. The return value should be 0 for success.
int (*readlink) (const char *, char *, size_t);
##Create a file node * * This is called for creation of all non-directory, non-symlink * nodes. If the filesystem defines a create() method, then for * regular files that will be called instead. */ int (*mknod) (const char *, mode_t, dev_t);
##Create a directory * * Note that the mode argument may not have the type specification * bits set, i.e. S_ISDIR(mode) can be false. To obtain the * correct directory type bits use mode|S_IFDIR * */ int (*mkdir) (const char *, mode_t);
##Remove a file int (*unlink) (const char *);
##Remove a directory int (*rmdir) (const char *);
##Create a symbolic link int (*symlink) (const char *, const char *);
##Rename a file
*
* flags may be RENAME_EXCHANGE or RENAME_NOREPLACE. If
* RENAME_NOREPLACE is specified, the filesystem must not
* overwrite newname if it exists and return an error
* instead. If RENAME_EXCHANGE is specified, the filesystem
* must atomically exchange the two files, i.e. both must
* exist and neither may be deleted.
*/
int (*rename) (const char *, const char *, unsigned int flags);
##Create a hard link to a file int (*link) (const char *, const char *);
##Change the permission bits of a file
*
* fi will always be NULL if the file is not currenly open, but
* may also be NULL if the file is open.
*/
int (*chmod) (const char *, mode_t, struct fuse_file_info *fi);
##Change the owner and group of a file
*
* fi will always be NULL if the file is not currenly open, but
* may also be NULL if the file is open.
*
* Unless FUSE_CAP_HANDLE_KILLPRIV is disabled, this method is
* expected to reset the setuid and setgid bits.
*/
int (*chown) (const char *, uid_t, gid_t, struct fuse_file_info *fi);
##Change the size of a file
*
* fi will always be NULL if the file is not currenly open, but
* may also be NULL if the file is open.
*
* Unless FUSE_CAP_HANDLE_KILLPRIV is disabled, this method is
* expected to reset the setuid and setgid bits.
*/
int (*truncate) (const char *, off_t, struct fuse_file_info *fi);
##Open a file
*
* Open flags are available in fi->flags. The following rules
* apply.
*
* - Creation (O_CREAT, O_EXCL, O_NOCTTY) flags will be
* filtered out / handled by the kernel.
*
* - Access modes (O_RDONLY, O_WRONLY, O_RDWR) should be used
* by the filesystem to check if the operation is
* permitted. If the -o default_permissions mount
* option is given, this check is already done by the
* kernel before calling open() and may thus be omitted by
* the filesystem.
*
* - When writeback caching is enabled, the kernel may send
* read requests even for files opened with O_WRONLY. The
* filesystem should be prepared to handle this.
*
* - When writeback caching is disabled, the filesystem is
* expected to properly handle the O_APPEND flag and ensure
* that each write is appending to the end of the file.
*
* - When writeback caching is enabled, the kernel will
* handle O_APPEND. However, unless all changes to the file
* come through the kernel this will not work reliably. The
* filesystem should thus either ignore the O_APPEND flag
* (and let the kernel handle it), or return an error
* (indicating that reliably O_APPEND is not available).
*
* Filesystem may store an arbitrary file handle (pointer,
* index, etc) in fi->fh, and use this in other all other file
* operations (read, write, flush, release, fsync).
*
* Filesystem may also implement stateless file I/O and not store
* anything in fi->fh.
*
* There are also some flags (direct_io, keep_cache) which the
* filesystem may set in fi, to change the way the file is opened.
* See fuse_file_info structure in <fuse_common.h> for more details.
*
* If this request is answered with an error code of ENOSYS
* and FUSE_CAP_NO_OPEN_SUPPORT is set in
* fuse_conn_info.capable, this is treated as success and
* future calls to open will also succeed without being send
* to the filesystem process.
*
*/
int (*open) (const char *, struct fuse_file_info *);
##Read data from an open file * * Read should return exactly the number of bytes requested except * on EOF or error, otherwise the rest of the data will be * substituted with zeroes. An exception to this is when the * 'direct_io' mount option is specified, in which case the return * value of the read system call will reflect the return value of * this operation. */ int (*read) (const char *, char *, size_t, off_t, struct fuse_file_info *);
##Write data to an open file * * Write should return exactly the number of bytes requested * except on error. An exception to this is when the 'direct_io' * mount option is specified (see read operation). * * Unless FUSE_CAP_HANDLE_KILLPRIV is disabled, this method is * expected to reset the setuid and setgid bits. */ int (*write) (const char *, const char *, size_t, off_t, struct fuse_file_info *);
##Get file system statistics * * The 'f_favail', 'f_fsid' and 'f_flag' fields are ignored */ int (*statfs) (const char *, struct statvfs *);
##Possibly flush cached data * * BIG NOTE: This is not equivalent to fsync(). It's not a * request to sync dirty data. * * Flush is called on each close() of a file descriptor. So if a * filesystem wants to return write errors in close() and the file * has cached dirty data, this is a good place to write back data * and return any errors. Since many applications ignore close() * errors this is not always useful. * * NOTE: The flush() method may be called more than once for each * open(). This happens if more than one file descriptor refers * to an opened file due to dup(), dup2() or fork() calls. It is * not possible to determine if a flush is final, so each flush * should be treated equally. Multiple write-flush sequences are * relatively rare, so this shouldn't be a problem. * * Filesystems shouldn't assume that flush will always be called * after some writes, or that if will be called at all. */ int (*flush) (const char *, struct fuse_file_info *);
##Release an open file * * Release is called when there are no more references to an open * file: all file descriptors are closed and all memory mappings * are unmapped. * * For every open() call there will be exactly one release() call * with the same flags and file descriptor. It is possible to * have a file opened more than once, in which case only the last * release will mean, that no more reads/writes will happen on the * file. The return value of release is ignored. */ int (*release) (const char *, struct fuse_file_info *);
##Synchronize file contents * * If the datasync parameter is non-zero, then only the user data * should be flushed, not the meta data. */ int (*fsync) (const char *, int, struct fuse_file_info *);
##Set extended attributes int (*setxattr) (const char *, const char *, const char *, size_t, int);
##Get extended attributes int (*getxattr) (const char *, const char *, char *, size_t);
##List extended attributes int (*listxattr) (const char *, char *, size_t);
##Remove extended attributes int (*removexattr) (const char *, const char *);
##Open directory * * Unless the 'default_permissions' mount option is given, * this method should check if opendir is permitted for this * directory. Optionally opendir may also return an arbitrary * filehandle in the fuse_file_info structure, which will be * passed to readdir, closedir and fsyncdir. */ int (*opendir) (const char *, struct fuse_file_info *);
##Read directory * * The filesystem may choose between two modes of operation: * * 1) The readdir implementation ignores the offset parameter, and * passes zero to the filler function's offset. The filler * function will not return '1' (unless an error happens), so the * whole directory is read in a single readdir operation. * * 2) The readdir implementation keeps track of the offsets of the * directory entries. It uses the offset parameter and always * passes non-zero offset to the filler function. When the buffer * is full (or an error happens) the filler function will return * '1'. */ int (*readdir) (const char *, void *, fuse_fill_dir_t, off_t, struct fuse_file_info *, enum fuse_readdir_flags);
##Release directory int (*releasedir) (const char *, struct fuse_file_info *);
##Synchronize directory contents * * If the datasync parameter is non-zero, then only the user data * should be flushed, not the meta data */ int (*fsyncdir) (const char *, int, struct fuse_file_info *);
*
* The return value will passed in the `private_data` field of
* `struct fuse_context` to all file operations, and as a
* parameter to the destroy() method. It overrides the initial
* value provided to fuse_main() / fuse_new().
*/
void *(*init) (struct fuse_conn_info *conn,
struct fuse_config *cfg);
##Clean up filesystem * * Called on filesystem exit. */ void (*destroy) (void *private_data);
##Check file access permissions * * This will be called for the access() system call. If the * 'default_permissions' mount option is given, this method is not * called. * * This method is not called under Linux kernel versions 2.4.x */ int (*access) (const char *, int);
##Create and open a file * * If the file does not exist, first create it with the specified * mode, and then open it. * * If this method is not implemented or under Linux kernel * versions earlier than 2.6.15, the mknod() and open() methods * will be called instead. */ int (*create) (const char *, mode_t, struct fuse_file_info *);
##Perform POSIX file locking operation * * The cmd argument will be either F_GETLK, F_SETLK or F_SETLKW. * * For the meaning of fields in 'struct flock' see the man page * for fcntl(2). The l_whence field will always be set to * SEEK_SET. * * For checking lock ownership, the 'fuse_file_info->owner' * argument must be used. * * For F_GETLK operation, the library will first check currently * held locks, and if a conflicting lock is found it will return * information without calling this method. This ensures, that * for local locks the l_pid field is correctly filled in. The * results may not be accurate in case of race conditions and in * the presence of hard links, but it's unlikely that an * application would rely on accurate GETLK results in these * cases. If a conflicting lock is not found, this method will be * called, and the filesystem may fill out l_pid by a meaningful * value, or it may leave this field zero. * * For F_SETLK and F_SETLKW the l_pid field will be set to the pid * of the process performing the locking operation. * * Note: if this method is not implemented, the kernel will still * allow file locking to work locally. Hence it is only * interesting for network filesystems and similar. */ int (*lock) (const char *, struct fuse_file_info *, int cmd, struct flock *);
*
* This supersedes the old utime() interface. New applications
* should use this.
*
* `fi` will always be NULL if the file is not currenly open, but
* may also be NULL if the file is open.
*
* See the utimensat(2) man page for details.
*/
int (*utimens) (const char *, const struct timespec tv[2],
struct fuse_file_info *fi);
##Map block index within file to block index within device * * Note: This makes sense only for block device backed filesystems * mounted with the 'blkdev' option */ int (*bmap) (const char *, size_t blocksize, uint64_t *idx);
##Ioctl * * flags will have FUSE_IOCTL_COMPAT set for 32bit ioctls in * 64bit environment. The size and direction of data is * determined by IOC*() decoding of cmd. For _IOC_NONE, * data will be NULL, for _IOC_WRITE data is out area, for * _IOC_READ in area and if both are set in/out area. In all * non-NULL cases, the area is of _IOC_SIZE(cmd) bytes. * * If flags has FUSE_IOCTL_DIR then the fuse_file_info refers to a * directory file handle. */ int (*ioctl) (const char *, int cmd, void *arg, struct fuse_file_info *, unsigned int flags, void *data);
##Poll for IO readiness events * * Note: If ph is non-NULL, the client should notify * when IO readiness events occur by calling * fuse_notify_poll() with the specified ph. * * Regardless of the number of times poll with a non-NULL ph * is received, single notification is enough to clear all. * Notifying more times incurs overhead but doesn't harm * correctness. * * The callee is responsible for destroying ph with * fuse_pollhandle_destroy() when no longer in use. */ int (*poll) (const char *, struct fuse_file_info *, struct fuse_pollhandle *ph, unsigned *reventsp);
##Write contents of buffer to an open file * * Similar to the write() method, but data is supplied in a * generic buffer. Use fuse_buf_copy() to transfer data to * the destination. * * Unless FUSE_CAP_HANDLE_KILLPRIV is disabled, this method is * expected to reset the setuid and setgid bits. */ int (*write_buf) (const char *, struct fuse_bufvec *buf, off_t off, struct fuse_file_info *);
##Store data from an open file in a buffer * * Similar to the read() method, but data is stored and * returned in a generic buffer. * * No actual copying of data has to take place, the source * file descriptor may simply be stored in the buffer for * later data transfer. * * The buffer must be allocated dynamically and stored at the * location pointed to by bufp. If the buffer contains memory * regions, they too must be allocated using malloc(). The * allocated memory will be freed by the caller. */ int (*read_buf) (const char *, struct fuse_bufvec **bufp, size_t size, off_t off, struct fuse_file_info *); ##Perform BSD file locking operation * * The op argument will be either LOCK_SH, LOCK_EX or LOCK_UN * * Nonblocking requests will be indicated by ORing LOCK_NB to * the above operations * * For more information see the flock(2) manual page. * * Additionally fi->owner will be set to a value unique to * this open file. This same value will be supplied to * ->release() when the file is released. * * Note: if this method is not implemented, the kernel will still * allow file locking to work locally. Hence it is only * interesting for network filesystems and similar. */ int (*flock) (const char *, struct fuse_file_info *, int op);
##Allocates space for an open file * * This function ensures that required space is allocated for specified * file. If this function returns success then any subsequent write * request to specified range is guaranteed not to fail because of lack * of space on the file system media. */ int (*fallocate) (const char *, int, off_t, off_t, struct fuse_file_info *);