dio_fcntl
(PHP 4 >= 4.2.0, PHP 5 < 5.1.0)
dio_fcntl — Performs a c library fcntl on fd
Description
The dio_fcntl() function performs the
operation specified by cmd
on the file
descriptor fd
. Some commands require
additional arguments args
to be supplied.
Parameters
-
fd
-
The file descriptor returned by dio_open().
-
cmd
-
Can be one of the following operations:
-
F_SETLK
- Lock is set or cleared. If the lock is held by someone else dio_fcntl() returns -1. -
F_SETLKW
- likeF_SETLK
, but in case the lock is held by someone else, dio_fcntl() waits until the lock is released. -
F_GETLK
- dio_fcntl() returns an associative array (as described below) if someone else prevents lock. If there is no obstruction key "type" will set toF_UNLCK
. -
F_DUPFD
- finds the lowest numbered available file descriptor greater than or equal toargs
and returns them. -
F_SETFL
- Sets the file descriptors flags to the value specified byargs
, which can beO_APPEND
,O_NONBLOCK
orO_ASYNC
. To useO_ASYNC
you will need to use the PCNTL extension.
-
-
args
-
args
is an associative array, whencmd
isF_SETLK
orF_SETLLW
, with the following keys:-
start
- offset where lock begins -
length
- size of locked area. zero means to end of file -
whence
- Where l_start is relative to: can beSEEK_SET
,SEEK_END
andSEEK_CUR
-
type
- type of lock: can beF_RDLCK
(read lock),F_WRLCK
(write lock) orF_UNLCK
(unlock)
-
Return Values
Returns the result of the C call.
Examples
Example #1 Setting and clearing a lock
<?php
$fd = dio_open('/dev/ttyS0', O_RDWR);
if (dio_fcntl($fd, F_SETLK, Array("type"=>F_WRLCK)) == -1) {
// the file descriptor appears locked
echo "The lock can not be cleared. It is held by someone else.";
} else {
echo "Lock successfully set/cleared";
}
dio_close($fd);
?>
Notes
Note: This function is not implemented on Windows platforms.