libc/sys/getfh.2

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.\"	@(#)getfh.2	8.1 (Berkeley) 6/9/93
.\" $FreeBSD$
.\"
.Dd September 23, 2020
.Dt GETFH 2
.Os
.Sh NAME
.Nm getfh ,
.Nm lgetfh ,
.Nm getfhat
.Nd get file handle
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.Ft int
.Fn getfh "const char *path" "fhandle_t *fhp"
.Ft int
.Fn lgetfh "const char *path" "fhandle_t *fhp"
.Ft int
.Fn getfhat "int fd" "const char *path" "fhandle_t *fhp" "int flag"
.Sh DESCRIPTION
The
.Fn getfh
system call
returns a file handle for the specified file or directory
in the file handle pointed to by
.Fa fhp .
.Pp
The
.Fn lgetfh
system call is like
.Fn getfh
except in the case where the named file is a symbolic link,
in which case
.Fn lgetfh
returns information about the link,
while
.Fn getfh
returns information about the file the link references.
.Pp
The
.Fn getfhat
system call is equivalent to
.Fn getfh
and
.Fn lgetfh
except when the
.Fa path
specifies a relative path, or the
.Dv AT_BENEATH
flag is provided.
For
.Fn getfhat
and relative
.Fa path ,
the status is retrieved from a file relative to
the directory associated with the file descriptor
.Fa fd
instead of the current working directory.
For
.Dv AT_BENEATH
and absolute
.Fa path ,
the status is retrieved from a file specified by the
.Fa path ,
but additional permission checks are performed, see below.
.Pp
The values for the
.Fa flag
are constructed by a bitwise-inclusive OR of flags from this list,
defined in
.In fcntl.h :
.Bl -tag -width indent
.It Dv AT_SYMLINK_NOFOLLOW
If
.Fa path
names a symbolic link, the status of the symbolic link is returned.
.It Dv AT_BENEATH
Only stat files and directories below the topping directory.
See the description of the
.Dv O_BENEATH
flag in the
.Xr open 2
manual page.
.It Dv AT_RESOLVE_BENEATH
Only walks paths below the topping directory.
See the description of the
.Dv O_RESOLVE_BENEATH
flag in the
.Xr open 2
manual page.
.El
.Pp
If
.Fn getfhat
is passed the special value
.Dv AT_FDCWD
in the
.Fa fd
parameter, the current working directory is used and the behavior is
identical to a call to
.Fn getfth
or
.Fn lgetfh
respectively, depending on whether or not the
.Dv AT_SYMLINK_NOFOLLOW
bit is set in
.Fa flag .
.Pp
When
.Fn getfhat
is called with an absolute
.Fa path
without the
.Dv AT_BENEATH
flag, it ignores the
.Fa fd
argument.
When
.Dv AT_BENEATH
is specified with an absolute
.Fa path ,
a directory passed by the
.Fa fd
argument is used as the topping point for the resolution.
These system calls are restricted to the superuser.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
The
.Fn getfh
and
.Fn lgetfh
system calls
fail if one or more of the following are true:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix of
.Fa path
is not a directory.
.It Bq Er ENAMETOOLONG
The length of a component of
.Fa path
exceeds 255 characters,
or the length of
.Fa path
exceeds 1023 characters.
.It Bq Er ENOENT
The file referred to by
.Fa path
does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix of
.Fa path .
.It Bq Er ELOOP
Too many symbolic links were encountered in translating
.Fa path .
.It Bq Er EFAULT
The
.Fa fhp
argument
points to an invalid address.
.It Bq Er EFAULT
The
.Fa path
argument
points to an invalid address.
.It Bq Er EIO
An
.Tn I/O
error occurred while reading from or writing to the file system.
.It Bq Er EINTEGRITY
Corrupted data was detected while reading from the file system.
.It Bq Er ESTALE
The file handle
.Fa fhp
is no longer valid.
.El
.Pp
In addition to the errors returned by
.Fn getfh ,
and
.Fn lgetfh ,
the
.Fn getfhat
system call may fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa path
argument does not specify an absolute path and the
.Fa fd
argument, is neither
.Dv AT_FDCWD
nor a valid file descriptor open for searching.
.It Bq Er EINVAL
The value of the
.Fa flag
argument is not valid.
.It Bq Er ENOTDIR
The
.Fa path
argument is not an absolute path and
.Fa fd
is neither
.Dv AT_FDCWD
nor a file descriptor associated with a directory.
.Sh SEE ALSO
.Xr fhopen 2 ,
.Xr open 2 ,
.Xr stat 2
.Sh HISTORY
The
.Fn getfh
system call first appeared in
.Bx 4.4 .