315 lines
7.7 KiB
Groff
315 lines
7.7 KiB
Groff
.\" $NetBSD: link.2,v 1.7 1995/02/27 12:34:01 cgd Exp $
|
|
.\"
|
|
.\" Copyright (c) 1980, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)link.2 8.3 (Berkeley) 1/12/94
|
|
.\"
|
|
.Dd June 3, 2021
|
|
.Dt LINK 2
|
|
.Os BSD 4
|
|
.Sh NAME
|
|
.Nm link ,
|
|
.Nm linkat
|
|
.Nd make a hard file link
|
|
.Sh SYNOPSIS
|
|
.Fd #include <unistd.h>
|
|
.Ft int
|
|
.Fo link
|
|
.Fa "const char *path1"
|
|
.Fa "const char *path2"
|
|
.Fc
|
|
.Ft int
|
|
.Fo linkat
|
|
.Fa "int fd1" "const char *name1" "int fd2" "const char *name2" "int flag"
|
|
.Fc
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn link
|
|
function call
|
|
atomically creates the specified directory entry (hard link)
|
|
.Fa path2
|
|
with the attributes of the underlying object pointed at by
|
|
.Fa path1 .
|
|
If the link is successful,
|
|
the link count of the underlying object is incremented;
|
|
.Fa path1
|
|
and
|
|
.Fa path2
|
|
share equal access and rights
|
|
to the
|
|
underlying object.
|
|
.Pp
|
|
If
|
|
.Fa path1
|
|
is removed, the file
|
|
.Fa path2
|
|
is not deleted and the link count of the
|
|
underlying object is
|
|
decremented.
|
|
.Pp
|
|
In order for the system call to succeed,
|
|
.Fa path1
|
|
must exist and both
|
|
.Fa path1
|
|
and
|
|
.Fa path2
|
|
must be in the same file system.
|
|
As mandated by POSIX.1,
|
|
.Fa path1
|
|
may not be a directory.
|
|
.Pp
|
|
.Fn link
|
|
will resolve and follow symbolic links contained within both
|
|
.Fa path1
|
|
and
|
|
.Fa path2 .
|
|
If the last component of
|
|
.Fa path1
|
|
is a symbolic link,
|
|
.Fn link
|
|
will point the hard link,
|
|
.Fa path2 ,
|
|
to the underlying object pointed to by
|
|
.Fa path1 ,
|
|
not to the symbolic link itself.
|
|
.Pp
|
|
The
|
|
.Fn linkat
|
|
system call is equivalent to
|
|
.Fa link
|
|
except in the case where either
|
|
.Fa name1
|
|
or
|
|
.Fa name2
|
|
or both are relative paths.
|
|
In this case a relative path
|
|
.Fa name1
|
|
is interpreted relative to
|
|
the directory associated with the file descriptor
|
|
.Fa fd1
|
|
instead of the current working directory and similarly for
|
|
.Fa name2
|
|
and the file descriptor
|
|
.Fa fd2 .
|
|
.Pp
|
|
Values for
|
|
.Fa flag
|
|
are constructed by a bitwise-inclusive OR of flags from the following
|
|
list, defined in
|
|
.In fcntl.h :
|
|
.Bl -tag -width indent
|
|
.It Dv AT_SYMLINK_FOLLOW
|
|
If
|
|
.Fa name1
|
|
names a symbolic link, a new link for the target of the symbolic link is
|
|
created.
|
|
.El
|
|
.Pp
|
|
If
|
|
.Fn linkat
|
|
is passed the special value
|
|
.Dv AT_FDCWD
|
|
in the
|
|
.Fa fd1
|
|
or
|
|
.Fa fd2
|
|
parameter, the current working directory is used for the respective
|
|
.Fa name
|
|
argument.
|
|
If both
|
|
.Fa fd1
|
|
and
|
|
.Fa fd2
|
|
have value
|
|
.Dv AT_FDCWD ,
|
|
the behavior is identical to a call to
|
|
.Fn link .
|
|
Unless
|
|
.Fa flag
|
|
contains the
|
|
.Dv AT_SYMLINK_FOLLOW
|
|
flag, if
|
|
.Fa name1
|
|
names a symbolic link, a new link is created for the symbolic link
|
|
.Fa name1
|
|
and not its target. On OS X, not assigning AT_SYMLINK_FOLLOW to
|
|
.Fa flag
|
|
may result in some file systems returning an error.
|
|
.Sh RETURN VALUES
|
|
Upon successful completion, a value of 0 is returned. Otherwise,
|
|
a value of -1 is returned and
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh ERRORS
|
|
.Fn link
|
|
will fail and no link will be created if:
|
|
.Bl -tag -width Er
|
|
.\" ==========
|
|
.It Bq Er EACCES
|
|
A component of either path prefix denies search permission.
|
|
.\" ==========
|
|
.It Bq Er EACCES
|
|
The requested link requires writing in a directory with a mode
|
|
that denies write permission.
|
|
.\" ==========
|
|
.It Bq Er EACCES
|
|
The current process cannot access the existing file.
|
|
.\" ==========
|
|
.It Bq Er EDQUOT
|
|
The directory in which the entry for the new link
|
|
is being placed cannot be extended because the
|
|
user's quota of disk blocks on the file system
|
|
containing the directory has been exhausted.
|
|
.\" ==========
|
|
.It Bq Er EEXIST
|
|
The link named by
|
|
.Fa path2
|
|
already exists.
|
|
.\" ==========
|
|
.It Bq Er EFAULT
|
|
One of the pathnames specified
|
|
is outside the process's allocated address space.
|
|
.\" ==========
|
|
.It Bq Er EIO
|
|
An I/O error occurs while reading from or writing to
|
|
the file system to make the directory entry.
|
|
.\" ==========
|
|
.It Bq Er ELOOP
|
|
Too many symbolic links are encountered in translating one of the pathnames.
|
|
This is taken to be indicative of a looping symbolic link.
|
|
.\" ==========
|
|
.It Bq Er EMLINK
|
|
The file already has {LINK_MAX} links.
|
|
.\" ==========
|
|
.It Bq Er ENAMETOOLONG
|
|
A component of a pathname exceeds
|
|
.Dv {NAME_MAX}
|
|
characters, or an entire path name exceeded
|
|
.Dv {PATH_MAX}
|
|
characters.
|
|
.\" ==========
|
|
.It Bq Er ENOENT
|
|
A component of either path prefix does not exist, or is a dangling symbolic link.
|
|
.\" ==========
|
|
.It Bq Er ENOENT
|
|
The file named by
|
|
.Fa path1
|
|
does not exist, or is a dangling symbolic link.
|
|
.\" ==========
|
|
.It Bq Er ENOSPC
|
|
The directory in which the entry for the new link is being placed
|
|
cannot be extended because there is no space left on the file
|
|
system containing the directory.
|
|
.\" ==========
|
|
.It Bq Er ENOTDIR
|
|
A component of either path prefix is not a directory.
|
|
.\" ==========
|
|
.It Bq Er EPERM
|
|
The file named by
|
|
.Fa path1
|
|
is a directory.
|
|
.\" ==========
|
|
.It Bq Er EROFS
|
|
The requested link requires writing in a directory
|
|
on a read-only file system.
|
|
.\" ==========
|
|
.It Bq Er EXDEV
|
|
The link named by
|
|
.Fa path2
|
|
and the file named by
|
|
.Fa path1
|
|
are on different file systems.
|
|
.\" ==========
|
|
.It Bq Er EDEADLK
|
|
The file named by
|
|
.Fa path1
|
|
is a
|
|
.Dq dataless
|
|
file that must be materialized before being linked and the I/O policy of
|
|
the current thread or process disallows file materialization
|
|
.Po see
|
|
.Xr getiopolicy_np 3
|
|
.Pc .
|
|
.El
|
|
.Pp
|
|
In addition to the errors returned by the
|
|
.Fn link ,
|
|
the
|
|
.Fn linkat
|
|
system call may fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
The
|
|
.Fa name1
|
|
or
|
|
.Fa name2
|
|
argument does not specify an absolute path and the
|
|
.Fa fd1
|
|
or
|
|
.Fa fd2
|
|
argument, respectively, 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 ENOTSUP
|
|
.Fa flag
|
|
was not set to
|
|
.Dv AT_SYMLINK_FOLLOW (some file systems only).
|
|
.It Bq Er ENOTSUP
|
|
The underlying file system does not support this call.
|
|
.It Bq Er ENOTDIR
|
|
The
|
|
.Fa name1
|
|
or
|
|
.Fa name2
|
|
argument is not an absolute path and
|
|
.Fa fd1
|
|
or
|
|
.Fa fd2 ,
|
|
respectively, is neither
|
|
.Dv AT_FDCWD
|
|
nor a file descriptor associated with a directory.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr symlink 2 ,
|
|
.Xr unlink 2
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn link
|
|
function is expected to conform to
|
|
.St -p1003.1-88 .
|
|
The
|
|
.Fn linkat
|
|
system call is expected to conform to POSIX.1-2008 .
|