(PHP 4 >= 4.2.0, PHP 5 < 5.1.0)
dio_fcntl — Performs a c library fcntl on fd
dio_fcntl ( resource $fd , int $cmd [, mixed $args ] ) : mixed
The dio_fcntl() function performs the operation specified by cmd
on the file descriptor fd
. Some commands require additional arguments args
to be supplied.
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 below) 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
whence
- 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)
Returns the result of the C call.
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); ?>
Note: This function is not implemented on Windows platforms.
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https://www.php.net/manual/en/function.dio-fcntl.php