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# dio_fcntl

(PHP 4 >= 4.2.0)

dio_fcntl -- Performs a c library fcntl on fd

## Description

mixed dio_fcntl ( resource fd, int cmd [, mixed arg])

The dio_fcntl() function performs the operation specified by `cmd` on the file descriptor `fd`. Some commands require additional arguments `args` to be supplied.

`arg` 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 or equal than `arg` and returns them.

- F_SETFL - Sets the file descriptors flags to the value specified by `arg`, Which can be O_APPEND,O_NONBLOCK or O_ASYNC . To use O_ASYNC you will need to use the pcntl extension.

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