Php dio fcntl () function

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(PHP 4 >= 4.2.0, PHP 5)

dio_fcntl -- Performs a c library fcntl on fd

Syntax

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);
?>

Note: This function is not implemented on Windows platforms.

Php dio fcntl Function syntax tag

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Php dio fcntl syntax tutorial

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