dio_fcntl
(PHP 4 >= 4.2.0, PHP 5 <= 5.0.5)
dio_fcntl — Performs a c library fcntl on fd
说明
mixed dio_fcntl
( resource $fd
, int $cmd
[, mixed $args
] )
The dio_fcntl() function performs the
operation specified by cmd
on the file
descriptor fd
. Some commands require
additional arguments args
to be supplied.
Note: 本函数未在 Windows 平台下实现。
参数
-
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 - like F_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 above) if someone else
prevents lock. If there is no obstruction key "type" will set
to F_UNLCK.
-
F_DUPFD - finds the lowest numbered available
file descriptor greater than or equal to args
and returns them.
-
F_SETFL - Sets the file descriptors flags to
the value specified by args
, which can be
O_APPEND, O_NONBLOCK or
O_ASYNC. To use O_ASYNC
you will need to use the PCNTL
extension.
-
args
-
args
is an associative array, when
cmd
is F_SETLK or
F_SETLLW, with the following keys:
-
"start" - offset where lock begins
-
"length" - size of locked area. zero means to end of file
-
"wenth" - Where l_start is relative to: can be
SEEK_SET,
SEEK_END and SEEK_CUR
-
"type" - type of lock: can be F_RDLCK (read
lock), F_WRLCK (write lock) or
F_UNLCK (unlock)
返回值
Returns the result of the C call.
范例
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 succesfully set/cleared";
}
dio_close($fd);
?>