wincache_lock(3) [php man page]

WINCACHE_LOCK(3)							 1							  WINCACHE_LOCK(3)

wincache_lock - Acquires an exclusive lock on a given key

SYNOPSIS

       bool wincache_lock (string  $key, [bool	$isglobal = false])

DESCRIPTION

	Obtains  an  exclusive	lock  on a given key. The execution of the current script will be blocked until the lock can be obtained. Once the
       lock is obtained, the other scripts that try to request the lock by using the same key will be blocked, until the current  script  releases
       the lock by using wincache_unlock(3).

       Warning

	       Using  of the wincache_lock(3) and wincache_unlock(3) can cause deadlocks when executing PHP scripts in a multi-process environment
	      like FastCGI. Do not use these functions unless you are absolutely sure you need to use them. For the majority of the operations	on
	      the user cache it is not necessary to use these functions.

PARAMETERS

	      o $key
		- Name of the key in the cache to get the lock on.

	      o $isglobal
		-  Controls  whether  the scope of the lock is system-wide or local. Local locks are scoped to the application pool in IIS FastCGI
		case or to all php processes that have the same parent process identifier.

RETURN VALUES

	Returns TRUE on success or FALSE on failure.

EXAMPLES

       Example #1

	      Using wincache_lock(3)

	      <?php
	      $fp = fopen("/tmp/lock.txt", "r+");
	      if (wincache_lock("lock_txt_lock")) { // do an exclusive lock
		  ftruncate($fp, 0); // truncate file
		  fwrite($fp, "Write something here
");
		  wincache_unlock("lock_txt_lock"); // release the lock
	      } else {
		  echo "Couldn't get the lock!";
	      }
	      fclose($fp);
	      ?>

SEE ALSO

       wincache_unlock(3),   wincache_ucache_set(3),	wincache_ucache_get(3),    wincache_ucache_delete(3),	 wincache_ucache_clear(3),    win-
       cache_ucache_exists(3), wincache_ucache_meminfo(3), wincache_ucache_info(3), wincache_scache_info(3).

PHP Documentation Group 													  WINCACHE_LOCK(3)

FLOCK(2)							System Calls Manual							  FLOCK(2)

NAME

       flock - apply or remove an advisory lock on an open file

SYNOPSIS

       #include <sys/file.h>

       #define	 LOCK_SH   1	/* shared lock */
       #define	 LOCK_EX   2	/* exclusive lock */
       #define	 LOCK_NB   4	/* don't block when locking */
       #define	 LOCK_UN   8	/* unlock */

       flock(fd, operation)
       int fd, operation;

DESCRIPTION

       Flock applies or removes an advisory lock on the file associated with the file descriptor fd.  A lock is applied by specifying an operation
       parameter that is the inclusive or of LOCK_SH or LOCK_EX and, possibly, LOCK_NB.  To unlock an existing lock operation should be LOCK_UN.

       Advisory locks allow cooperating processes to perform consistent operations on files, but do not guarantee consistency (i.e., processes may
       still access files without using advisory locks possibly resulting in inconsistencies).

       The  locking  mechanism allows two types of locks: shared locks and exclusive locks.  At any time multiple shared locks may be applied to a
       file, but at no time are multiple exclusive, or both shared and exclusive, locks allowed simultaneously on a file.

       A shared lock may be upgraded to an exclusive lock, and vice versa, simply by specifying the appropriate lock type;  this  results  in  the
       previous lock being released and the new lock applied (possibly after other processes have gained and released the lock).

       Requesting  a lock on an object that is already locked normally causes the caller to be blocked until the lock may be acquired.	If LOCK_NB
       is included in operation, then this will not happen; instead the call will fail and the error EWOULDBLOCK will be returned.

NOTES

       Locks are on files, not file descriptors.  That is, file descriptors duplicated through	dup(2)	or  fork(2)  do  not  result  in  multiple
       instances of a lock, but rather multiple references to a single lock.  If a process holding a lock on a file forks and the child explicitly
       unlocks the file, the parent will lose its lock.

       Processes blocked awaiting a lock may be awakened by signals.

RETURN VALUE

       Zero is returned if the operation was successful; on an error a -1 is returned and an error code is left in the global location errno.

ERRORS

       The flock call fails if:

       [EWOULDBLOCK]	   The file is locked and the LOCK_NB option was specified.

       [EBADF]		   The argument fd is an invalid descriptor.

       [EINVAL] 	   The argument fd refers to an object other than a file.

SEE ALSO

       open(2), close(2), dup(2), execve(2), fork(2)

4.2 Berkeley Distribution					   May 22, 1986 							  FLOCK(2)