Description
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.
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)
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.
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);
?>
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Note: This function is not
implemented on Windows platforms.
