有时候你的php脚本或许需要线程安全的保证,比如进行文件写操作的时候。本文提供了文件加锁函数以及使用示例。文件加锁功能也可以用来获得独享的处理空间,防止脚本执行发生同步错误。
代码如下:
/*************************************************************************
*file lock
*@author Zeal Li
*http://www.zeali.net/
*
*************************************************************************/
/*
*lock_thisfile:获得独享锁
*@param $tmpFileStr 用来作为共享锁文件的文件名(可以随便起一个名字)
*@param $locktype 锁类型,缺省为false(非阻塞型,也就是一旦加锁失败则直接返回false),设置为true则会一直等待加锁成功才返回
*@return 如果加锁成功,则返回锁实例(当使用unlock_thisfile方法的时候需要这个参数),加锁失败则返回false.
*/
function lock_thisfile($tmpFileStr,$locktype=false){
if($locktype == false)
$locktype = LOCK_EX|LOCK_NB;
$can_write = 0;
$lockfp = @fopen($tmpFileStr.".lock","w");
if($lockfp){
$can_write = @flock($lockfp,$locktype);
}
if($can_write){
return $lockfp;
}
else{
if($lockfp){
@fclose($lockfp);
@unlink($tmpFileStr.".lock");
}
return false;
}
}
/**
*unlock_thisfile:对先前取得的锁实例进行解锁
*@param $fp lock_thisfile方法的返回值
*@param $tmpFileStr 用来作为共享锁文件的文件名(可以随便起一个名字)
*/
function unlock_thisfile($fp,$tmpFileStr){
@flock($fp,LOCK_UN);
@fclose($fp);
@fclose($fp);
@unlink($tmpFileStr.".lock");
}
?>
代码如下:
// 使用举例
$tmpFileStr = "/tmp/mylock.loc";
// 等待取得操作权限,如果要立即返回则把第二个参数设为false.
$lockhandle = lock_thisfile($tmpFileStr,true);
if($lockhandle){
// 在这里进行所有需要独占的事务处理。
// ... ...
// 事务处理完毕。
unlock_thisfile($lockhandle,$tmpFileStr);
}
?>

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