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

FD_CLOEXEC

FD_CLOEXEC

the value of the close-on-exec flag.

F_DUPFD

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