Php/docs/function.dio-fcntl

• PHP Manual
• Direct IO Functions
• Performs a c library fcntl on fd

dio_fcntl

(PHP 4 >= 4.2.0, PHP 5 < 5.1.0)

dio_fcntl — Performs a c library fcntl on fd

Description

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.

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 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)

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 successfully set/cleared";}dio_close($fd);?>

Notes

Note:

This function is not

implemented on Windows platforms.