to clarify:
in unix/linux:
hardlinks (by this function) cannot go across different filesystems.
softlinks can point anywhere.
in linux, hardlinking to directory is not permited.
(PHP 4, PHP 5, PHP 7, PHP 8)
link — 建立一个硬连接
$target, string $link): boollink() 建立一个硬连接。
target要链接的目标。
link链接的名称。
成功时返回 true， 或者在失败时返回 false。
如果 link 已存在或者 target
不存在，此函数会失败并发出 E_WARNING。
示例 #1 创建简单的硬链接
<?php
$target = 'source.ext'; // This is the file that already exists
$link = 'newfile.ext'; // This the filename that you want to link it to
link($target, $link);
?>to clarify:
in unix/linux:
hardlinks (by this function) cannot go across different filesystems.
softlinks can point anywhere.
in linux, hardlinking to directory is not permited.For a backup utility I needed link-like functionality on a windows system. As it isn't availible on windows, i tried to do it myself with the help of some tools. All you need is junction.exe from sysinternals in your %PATH%.
<?php
if(!function_exists('link')){ // Assume a windows system
function link($target, $link){
if(is_dir($target)){
// junctions link to directories in windows
exec("junction $link $target", $lines, $val);
return 0 == $val;
}elseif(is_file($target)){
// Hardlinks link to files in windows
exec("fsutil hardlink create $link $target", $lines, $val);
return 0 == $val;
}
return false;
}
}
?>
http://www.sysinternals.com/Utilities/Junction.htmlI noticed that, differently from Unix ln command, the second parameter can´t be a directory name, i.e., if you want to create a link with the same filename of the target file (obviously on different directories), you must specify the filename on the link parameter.
Example:
Unix ln command:
ln /dir1/file /dir2/ // ok, creates /dir2/file link
PHP link function:
link ("/dir1/file", "/dir2/"); // wrong, gives a "File exists" warning
link ("/dir1/file", "/dir2/file"); // ok, creates /dir2/file linkIn at least php-5.3 (linux-2.6.38.6) a process owned by apache could make a link() in a directory owned by apache, to a file owned by webmaster to which it had group read permissions. In php-7.0 (linux-4.13.16) that results in a "permission denied". Either the target file must be owned by apache or one must use copy() instead (so that ownership changes to apache).