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.\" $OpenBSD: fuse_reply_err.3,v 1.1 2026/02/01 20:02:58 helg Exp $
.\"
.\" Copyright (c) 2026 Helg Bredow <helg@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: February 1 2026 $
.Dt FUSE_REPLY_ERR 3
.Os
.Sh NAME
.Nm fuse_reply_err ,
.Nm fuse_reply_buf ,
.Nm fuse_reply_attr ,
.Nm fuse_reply_open ,
.Nm fuse_reply_write ,
.Nm fuse_reply_entry ,
.Nm fuse_reply_statfs ,
.Nm fuse_reply_readlink
.Nd send replies to FUSE requests
.Sh SYNOPSIS
.Lb libfuse
.In fuse_lowlevel.h
.Ft int
.Fo fuse_reply_err
.Fa "fuse_req_t req"
.Fa "int errno"
.Fc
.Ft int
.Fo fuse_reply_buf
.Fa "fuse_req_t req"
.Fa "const char *buf"
.Fa "off_t size"
.Fc
.Ft int
.Fo fuse_reply_attr
.Fa "fuse_req_t req"
.Fa "const struct stat *attr"
.Fa "double attr_timeout"
.Fc
.Ft int
.Fo fuse_reply_open
.Fa "fuse_req_t req"
.Fa "const struct fuse_file_info *fi"
.Fc
.Ft int
.Fo fuse_reply_write
.Fa "fuse_req_t req"
.Fa "size_t count"
.Fc
.Ft int
.Fo fuse_reply_entry
.Fa "fuse_req_t req"
.Fa "const struct fuse_entry_param *e"
.Fc
.Ft int
.Fo fuse_reply_statfs
.Fa "fuse_req_t req"
.Fa "const struct statvfs *stbuf"
.Fc
.Ft int
.Fo fuse_reply_readlink
.Fa "fuse_req_t req"
.Fa "char *linkname"
.Fc
.Sh DESCRIPTION
These functions are used in the FUSE low-level API to send responses to
requests received from the kernel.
.Pp
Once called, the request is considered handled and must not be replied to
again.
.Bl -tag -width Ds
.It Fn fuse_reply_err "req" "errno"
Send an error response to the request
.Fa req .
The
.Fa errno
parameter must be a valid (non-negated) error number, for example
.Er ENOENT
or
.Er EACCES ..
.Pp
This is a valid response for all file system operations.
.It Fn fuse_reply_buf "req" "buf" "size"
Send a buffer
.Fa buf
of
.Fa size
bytes of data to the kernel.
.Pp
This is a valid response for
.Fn read
and
.Fn readdir
operations.
.It Fn fuse_reply_attr "req" "attr" "attr_timeout"
Replies with file attributes specified in
.Fa attr ,
valid for
.Fa attr_timeout
seconds.
The
.Ox
kernel does not currently support attribute caching and
.Fa attr_timeout
will be ignored.
.Pp
This is a valid response for
.Fn getattr
and
.Fn setattr
operations.
.It Fn fuse_reply_open "req" "ffi"
Send a response to an open request with the file info structure
.Fa ffi .
Only the
.Fa fh
member of
.Fa ffi
is used.
.Pp
This is a valid response for
.Fn open
and
.Fn opendir
operations.
.It Fn fuse_reply_write "req" "count"
Reply to a write request with the
.Fa count
of bytes written.
.Pp
This is a valid response for the
.Fn write
operation.
.It Fn fuse_reply_entry "req" "e"
Reply to a lookup or other request that results in new file creation with
the details of the new directory entry
.Fa e ,
which is defined as follows:
.Bd -literal
struct fuse_entry_param {
ino_t ino; /* inode number of the entry */
unsigned long generation; /* must be non-zero */
struct stat attr; /* attributes of the entry */
double attr_timeout; /* ignored */
double entry_timeout; /* ignored */
};
.Ed
.Pp
The
.Ox
kernel does not currently cache FUSE lookups or attributes and the
.Fa attr_timeout
and
.Fa entry_timeout
members are ignored.
.Pp
This is a valid response for the
.Fn lookup ,
.Fn mknod ,
.Fn mkdir ,
.Fn symlink , and
.Fn link
operations.
.It Fn fuse_reply_statfs "req" "stbuf"
Reply with file system statistics provided in
.Fa stbuf .
.Pp
This is a valid response for the
.Fn statfs
operation.
.It Fn fuse_reply_readlink "req" "link"
Replies to a readlink request with the symbolic link path
.Fa link .
The target string cannot contain the NUL character.
.Pp
This is a valid response for the
.Fn readlink
operation.
.El
.Sh RETURN VALUES
All functions return 0 on success.
On failure, they return
.Pf \- Va errno
to indicate the error.
.Sh SEE ALSO
.Xr fuse_lowlevel_new 3
.Sh STANDARDS
These library functions conform to FUSE 2.6.
.Sh HISTORY
These library functions have been available since
.Ox 7.9 .
.Sh AUTHORS
.An Helg Bredow Aq Mt helg@openbsd.org
|
