dio_fcntl
(PHP 4 >= 4.2.0, PHP 5 <= 5.0.5)
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 - 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)
-
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 succesfully set/cleared";
}
dio_close($fd);
?>
Notes
Note: This function is not implemented on Windows platforms.