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LINK(2) | System Calls Manual | LINK(2) |
NAME¶
link
,
linkat
—
make a hard file link
LIBRARY¶
Standard C Library (libc, -lc)SYNOPSIS¶
#include
<unistd.h>
int
link
(const
char *name1,
const char
*name2);
int
linkat
(int
fd1, const char *name1,
int fd2, const
char *name2, int flag);
DESCRIPTION¶
Thelink
() system call atomically creates the
specified directory entry (hard link) name2
with the attributes of the underlying object pointed at by
name1. If the link is successful: the link
count of the underlying object is incremented;
name1 and
name2 share equal access and rights to the
underlying object.
If name1 is removed, the file
name2 is not deleted and the link count of
the underlying object is decremented.
The object pointed at by the name1 argument
must exist for the hard link to succeed and both
name1 and
name2 must be in the same file system. The
name1 argument may not be a directory.
The linkat
() system call is equivalent to
link except in the case where either
name1 or
name2 or both are relative paths. In this
case a relative path name1 is interpreted
relative to the directory associated with the file descriptor
fd1 instead of the current working directory
and similarly for name2 and the file
descriptor fd2.
Values for flag are constructed by a
bitwise-inclusive OR of flags from the following list, defined in
<fcntl.h>
:
AT_SYMLINK_FOLLOW
- If name1 names a symbolic link, a new link for the target of the symbolic link is created.
linkat
() is passed the special value
AT_FDCWD
in the
fd1 or fd2
parameter, the current working directory is used for the respective
name argument. If both
fd1 and fd2
have value AT_FDCWD
, the behavior is
identical to a call to link
(). Unless
flag contains the
AT_SYMLINK_FOLLOW
flag, if
name1 names a symbolic link, a new link is
created for the symbolic link name1 and not
its target.
RETURN VALUES¶
Thelink
() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno is set to indicate
the error.
ERRORS¶
Thelink
() system call will fail and no link
will be created if:
- [
ENOTDIR
] - A component of either path prefix is not a directory.
- [
ENAMETOOLONG
] - A component of either pathname exceeded 255 characters, or entire length of either path name exceeded 1023 characters.
- [
ENOENT
] - A component of either path prefix does not exist.
- [
EOPNOTSUPP
] - The file system containing the file named by name1 does not support links.
- [
EMLINK
] - The link count of the file named by name1 would exceed 32767.
- [
EACCES
] - A component of either path prefix denies search permission.
- [
EACCES
] - The requested link requires writing in a directory with a mode that denies write permission.
- [
ELOOP
] - Too many symbolic links were encountered in translating one of the pathnames.
- [
ENOENT
] - The file named by name1 does not exist.
- [
EEXIST
] - The link named by name2 does exist.
- [
EPERM
] - The file named by name1 is a directory.
- [
EPERM
] - The file named by name1 has its immutable or append-only flag set, see the chflags(2) manual page for more information.
- [
EPERM
] - The parent directory of the file named by name2 has its immutable flag set.
- [
EXDEV
] - The link named by name2 and the file named by name1 are on different file systems.
- [
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.
- [
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.
- [
EIO
] - An I/O error occurred while reading from or writing to the file system to make the directory entry.
- [
EROFS
] - The requested link requires writing in a directory on a read-only file system.
- [
EFAULT
] - One of the pathnames specified is outside the process's allocated address space.
link
(), the
linkat
() system call may fail if:
- [
EBADF
] - The name1 or
name2 argument does not specify an
absolute path and the fd1 or
fd2 argument, respectively, is neither
AT_FDCWD
nor a valid file descriptor open for searching. - [
EINVAL
] - The value of the flag argument is not valid.
- [
ENOTDIR
] - The name1 or
name2 argument is not an absolute path
and fd1 or
fd2, respectively, is neither
AT_FDCWD
nor a file descriptor associated with a directory.
SEE ALSO¶
chflags(2), readlink(2), symlink(2), unlink(2)STANDARDS¶
Thelink
() system call is expected to conform
to IEEE Std 1003.1-1990
(“POSIX.1”). The
linkat
() system call follows The Open Group
Extended API Set 2 specification.
HISTORY¶
Thelink
() function appeared in
Version 7 AT&T UNIX. The
linkat
() system call appeared in
FreeBSD 8.0.
The link
() system call traditionally allows
the super-user to link directories which corrupts the file system coherency.
This implementation no longer permits it.April 10, 2008 | Debian |