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# flock

flock -- portable advisory file locking

## Description

`bool flock`(int fp, int operation);

PHP supports a portable way of locking complete files in an advisory way (which means all accessing programs have to use the same way of locking or it will not work).

flock() operates on `fp` which must be an open file pointer. `operation` is one of the following values:

- To acquire a shared lock (reader), set `operation` to 1.

- To acquire an exclusive lock (writer), set `operation` to 2.

- To release a lock (shared or exclusive), set `operation` to 3.

- If you don't want flock() to block while locking, add 4 to `operation`.

flock() allows you to perform a simple reader/writer model which can be used on virtually every platform (including most Unices and even Windows).

flock() returns true on success and false on error (e.g. when a lock could not be acquired).

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