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.Dd November 30, 2022 .Dt FHLINK 2 .Os .Sh NAME .Nm fhlink , .Nm fhlinkat .Nd make a hard file link .Sh LIBRARY .Lb libc .Sh SYNOPSIS n unistd.h .Ft int .Fn fhlink "fhandle_t *fhp" "const char *to" .Ft int .Fn fhlinkat "fhandle_t *fhp" "int tofd" "const char *to" .Fc .Sh DESCRIPTION The .Fn fhlink system call atomically creates the specified directory entry (hard link) .Fa to with the attributes of the underlying object pointed at by .Fa fhp . If the link is successful: the link count of the underlying object is incremented; .Fa fhp and .Fa to share equal access and rights to the underlying object.
p If .Fa fhp is removed, the file .Fa to is not deleted and the link count of the underlying object is decremented.
p The object pointed at by the .Fa fhp argument must exist for the hard link to succeed and both .Fa fhp and .Fa to must be in the same file system. The .Fa fhp argument may not be a directory.
p The .Fn fhlinkat system call is equivalent to .Fa fhlink except in the case where .Fa to is a relative paths. In this case a relative path .Fa to is interpreted relative to the directory associated with the file descriptor .Fa tofd instead of the current working directory.
p If .Fn fhlinkat is passed the special value .Dv AT_FDCWD in the .Fa tofd parameter, the current working directory is used for the .Fa to argument. If .Fa tofd has 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 fhp names a symbolic link, a new link is created for the symbolic link .Fa fhp and not its target. .Sh RETURN VALUES .Rv -std link .Sh ERRORS The .Fn fhlink system call will fail and no link will be created if: l -tag -width Er t Bq Er ENOTDIR A component of .Fa to prefix is not a directory. t Bq Er ENAMETOOLONG A component of .Fa to exceeded 255 characters, or entire length of .Fa to name exceeded 1023 characters. t Bq Er ENOENT A component of .Fa to prefix does not exist. t Bq Er EOPNOTSUPP The file system containing the file pointed at by .Fa fhp does not support links. t Bq Er EMLINK The link count of the file pointed at by .Fa fhp would exceed 32767. t Bq Er EACCES A component of .Fa to prefix denies search permission. t Bq Er EACCES The requested link requires writing in a directory with a mode that denies write permission. t Bq Er ELOOP Too many symbolic links were encountered in translating one of the pathnames. t Bq Er ENOENT The file pointed at by .Fa fhp does not exist. t Bq Er EEXIST The link named by .Fa to does exist. t Bq Er EPERM The file pointed at by .Fa fhp is a directory. t Bq Er EPERM The file pointed at by .Fa fhp has its immutable or append-only flag set, see the .Xr chflags 2 manual page for more information. t Bq Er EPERM The parent directory of the file named by .Fa to has its immutable flag set. t Bq Er EXDEV The link named by .Fa to and the file pointed at by .Fa fhp are on different file systems. t 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. t 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. t Bq Er EIO An I/O error occurred while reading from or writing to the file system to make the directory entry. t Bq Er EINTEGRITY Corrupted data was detected while reading from the file system. t Bq Er EROFS The requested link requires writing in a directory on a read-only file system. t Bq Er EFAULT One of the pathnames specified is outside the process's allocated address space. t Bq Er ESTALE The file handle .Fa fhp is no longer valid .El
p In addition to the errors returned by the .Fn fhlink , the .Fn fhlinkat system call may fail if: l -tag -width Er t Bq Er EBADF The .Fa fhp or .Fa to argument does not specify an absolute path and the .Fa tofd argument, is not .Dv AT_FDCWD nor a valid file descriptor open for searching. t Bq Er EINVAL The value of the .Fa flag argument is not valid. t Bq Er ENOTDIR The .Fa fhp or .Fa to argument is not an absolute path and .Fa tofd is not .Dv AT_FDCWD nor a file descriptor associated with a directory. .El .Sh SEE ALSO .Xr fhopen 2 , .Xr fhreadlink 2 , .Xr fhstat 2 .Sh HISTORY The .Fn fhlink and .Fn fhlinkat system calls first appeared in .Fx 12.1 .