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<HTML
><HEAD
><TITLE
>flock</TITLE
><META
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><H1
><A
NAME="function.flock"
>flock</A
></H1
><DIV
CLASS="refnamediv"
><A
NAME="AEN11120"
></A
><P
> (PHP3 >= 3.0.7, PHP4 )</P
>flock -- Portable advisory file locking</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN11123"
></A
><H2
>Description</H2
><DIV
CLASS="funcsynopsis"
><A
NAME="AEN11125"
></A
><P
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>bool <B
CLASS="function"
>flock</B
></CODE
> (int fp, int operation [, int
wouldblock])</CODE
></P
><P
></P
></DIV
><P
> 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).
</P
><P
> <B
CLASS="function"
>flock()</B
> operates on <TT
CLASS="parameter"
><I
>fp</I
></TT
>
which must be an open file
pointer. <TT
CLASS="parameter"
><I
>operation</I
></TT
> is one of the following
values:
</P
><P
> <P
></P
><UL
><LI
><P
> To acquire a shared lock (reader), set
<TT
CLASS="parameter"
><I
>operation</I
></TT
> to LOCK_SH (set to 1 prior to
PHP 4.0.1).
</P
></LI
><LI
><P
> To acquire an exclusive lock (writer), set
<TT
CLASS="parameter"
><I
>operation</I
></TT
> to LOCK_EX (set to 2 prior to
PHP 4.0.1).
</P
></LI
><LI
><P
> To release a lock (shared or exclusive), set
<TT
CLASS="parameter"
><I
>operation</I
></TT
> to LOCK_UN (set to 3 prior to
PHP 4.0.1).
</P
></LI
><LI
><P
> If you don't want <B
CLASS="function"
>flock()</B
> to block while
locking, add LOCK_NB (4 prior to PHP 4.0.1) to
<TT
CLASS="parameter"
><I
>operation</I
></TT
>.
</P
></LI
></UL
>
</P
><P
> <B
CLASS="function"
>Flock()</B
> allows you to perform a simple
reader/writer model which can be used on virtually every platform
(including most Unices and even Windows). The optional 3rd
argument is set to true if the lock would block (EWOULDBLOCK
errno condition)
</P
><P
> <B
CLASS="function"
>Flock()</B
> returns true on success and false on
error (e.g. when a lock could not be acquired).
</P
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