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 — Criando uma ligação rígida
target
Alvo da ligação.
link
O nome da ligação.
Retorna true
em caso de sucesso ou false
em caso de falha.
A função falha e emite um E_WARNING
se link
já existir, ou se target
não existir.
Exemplo #1 Criando uma ligação rígida
<?php
$target = 'source.ext'; // Esse é o arquivo existente
$link = 'newfile.ext'; // Esse é o nome da ligação
link($target, $link);
?>
Nota: Esta função não funcionará em arquivos remotos, pois o arquivo a ser examinado deve ser acessível através do sistema de arquivos do servidor.
Nota: No Windows, essa função requer o PHP rodando em nível elevado de privilégios ou com o UAC desabilitado.
to clarify:
in unix/linux:
hardlinks (by this function) cannot go across different filesystems.
softlinks can point anywhere.
in linux, hardlinking to directory is not permited.
For a backup utility I needed link-like functionality on a windows system. As it isn't availible on windows, i tried to do it myself with the help of some tools. All you need is junction.exe from sysinternals in your %PATH%.
<?php
if(!function_exists('link')){ // Assume a windows system
function link($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.html
I 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 link
In 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).