readlink()

(PHP 4, PHP 5, PHP 7)

返回符号连接指向的目标

说明

readlink(string $path): string

readlink()和同名的 C 函数做同样的事，返回符号连接的内容。

参数

$path

链接符号的路径。

更新日志

返回值

返回链接的路径内容，出错则返回FALSE。

范例

Example #1readlink()例

<?php
// output e.g. /boot/vmlinux-2.4.20-xfs
echo readlink('/vmlinuz');
?>

参见

• is_link() 判断给定文件名是否为一个符号连接
• symlink() 建立符号连接
• linkinfo() 获取一个连接的信息

This will trigger a warning and return false if you pass it a non-symlink. If the file doesn't exist, it will trigger a differently worded warning.
mslade@jupiter ~$ touch a
mslade@jupiter ~$ ln -s a b
mslade@jupiter ~$ ls -l {a,b}
-rw------- 1 mslade mslade 0 2009-06-10 15:27 a
lrwxrwxrwx 1 mslade mslade 1 2009-06-10 15:27 b -> a
mslade@jupiter ~$ php -r "var_dump(readlink('b'));"
string(1) "a"
mslade@jupiter ~$ php -r "var_dump(readlink('a'));"
Warning: readlink(): Invalid argument in Command line code on line 1
bool(false)
mslade@jupiter ~$ php -r "var_dump(readlink('c'));"
Warning: readlink(): No such file or directory in Command line code on line 1
bool(false)

A little function to readlink TO THE END:
(realpath can't do this if the symlink (ultimately) points to a non-existing path, since it just returns false in this case.)
function readlinkToEnd($linkFilename) {
 if(!is_link($linkFilename)) return $linkFilename;
 $final = $linkFilename;
 while(true) {
  $target = readlink($final);
  if(substr($target, 0, 1)=='/') $final = $target;
  else $final = dirname($final).'/'.$target;
  if(substr($final, 0, 2)=='./') $final = substr($final, 2);
  if(!is_link($final)) return $final;
 }
}

A little function to readlink TO THE END:
(realpath can't do this if the symlink (ultimately) points to a non-existing path, since it just returns false in this case.)
function readlinkToEnd($linkFilename) {
 if(!is_link($linkFilename)) return $linkFilename;
 $final = $linkFilename;
 while(true) {
  $target = readlink($final);
  if(substr($target, 0, 1)=='/') $final = $target;
  else $final = dirname($final).'/'.$target;
  if(substr($final, 0, 2)=='./') $final = substr($final, 2);
  if(!is_link($final)) return $final;
 }
}

It is neccesary to be notified that readlink only works for a real link file, if this link file locates to a directory, you cannot detect and read its contents, the is_link() function will always return false and readlink() will display a warning is you try to do. Like the following codes:
<?php
//assume that A is a directory located in C:, B is a symlink to A, and A contents a file named C.
echo is_link('B/C'); //false
echo readlink('B/C'); //false and a warning will be displayed
//instead, you should use realpath() function to get the real path of C
echo realpath('B/C'); //C:\A\C
?>