Fcntl

Fcntl loads the constants defined in the system's <fcntl.h> C header file, and used with both the fcntl(2) and open(2) POSIX system calls.

To perform a fcntl(2) operation, use IO::fcntl.

To perform an open(2) operation, use IO.sysopen.

The set of operations and constants available depends upon specific operating system. Some values listed below may not be supported on your system.

See your fcntl(2) man page for complete details.

Open /tmp/tempfile as a write-only file that is created if it doesn't exist:

require 'fcntl'

fd = IO.sysopen('/tmp/tempfile',
                Fcntl::O_WRONLY | Fcntl::O_EXCL | Fcntl::O_CREAT)
f = IO.open(fd)
f.syswrite("TEMP DATA")
f.close

Get the flags on file s:

m = s.fcntl(Fcntl::F_GETFL, 0)

Set the non-blocking flag on f in addition to the existing flags in m.

f.fcntl(Fcntl::F_SETFL, Fcntl::O_NONBLOCK|m)

Constants

F_DUPFD	=	Document-const
	F_DUPFD Duplicate a file descriptor to the mimimum unused file descriptor greater than or equal to the argument. The close-on-exec flag of the duplicated file descriptor is set. (Ruby uses F_DUPFD_CLOEXEC internally if available to avoid race condition. F_SETFD is used if F_DUPFD_CLOEXEC is not available.)
F_GETFD	=	Document-const
	F_GETFD Read the close-on-exec flag of a file descriptor.
F_GETLK	=	Document-const
	F_GETLK Determine whether a given region of a file is locked. This uses one of the F_*LK flags.
F_SETFD	=	Document-const
	F_SETFD Set the close-on-exec flag of a file descriptor.
F_GETFL	=	Document-const
	F_GETFL Get the file descriptor flags. This will be one or more of the O_* flags.
F_SETFL	=	Document-const
	F_SETFL Set the file descriptor flags. This will be one or more of the O_* flags.
F_SETLK	=	Document-const
	F_SETLK Acquire a lock on a region of a file. This uses one of the F_*LCK flags.
F_SETLKW	=	Document-const
	F_SETLKW Acquire a lock on a region of a file, waiting if necessary. This uses one of the F_*LCK flags
FD_CLOEXEC	=	Document-const
	FD_CLOEXEC the value of the close-on-exec flag.
F_RDLCK	=	Document-const
	F_RDLCK Read lock for a region of a file
F_UNLCK	=	Document-const
	F_UNLCK Remove lock for a region of a file
F_WRLCK	=	Document-const
	F_WRLCK Write lock for a region of a file
O_CREAT	=	Document-const
	O_CREAT Create the file if it doesn't exist
O_EXCL	=	Document-const
	O_EXCL Used with O_CREAT, fail if the file exists
O_NOCTTY	=	Document-const
	O_NOCTTY Open TTY without it becoming the controlling TTY
O_TRUNC	=	Document-const
	O_TRUNC Truncate the file on open
O_APPEND	=	Document-const
	O_APPEND Open the file in append mode
O_NONBLOCK	=	Document-const
	O_NONBLOCK Open the file in non-blocking mode
O_NDELAY	=	Document-const
	O_NDELAY Open the file in non-blocking mode
O_RDONLY	=	Document-const
	O_RDONLY Open the file in read-only mode
O_RDWR	=	Document-const
	O_RDWR Open the file in read-write mode
O_WRONLY	=	Document-const
	O_WRONLY Open the file in write-only mode.
O_ACCMODE	=	Document-const
	O_ACCMODE Mask to extract the read/write flags

Module Fcntl