Module: Fcntl

Defined in:

ext/fcntl/fcntl.c,
ext/fcntl/fcntl.c

Overview

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)

Constant Summary

VERSION =

The version string.

rb_str_new_cstr(FCNTL_VERSION)

F_DUPFD =

Duplicate a file descriptor to the minimum 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.)

INT2NUM(F_DUPFD)

F_GETFD =

Read the close-on-exec flag of a file descriptor.

INT2NUM(F_GETFD)

F_GETLK =

Determine whether a given region of a file is locked. This uses one of the F_*LK flags.

INT2NUM(F_GETLK)

F_SETFD =

Set the close-on-exec flag of a file descriptor.

INT2NUM(F_SETFD)

F_GETFL =

Get the file descriptor flags. This will be one or more of the O_* flags.

INT2NUM(F_GETFL)

F_SETFL =

Set the file descriptor flags. This will be one or more of the O_* flags.

INT2NUM(F_SETFL)

F_SETLK =

Acquire a lock on a region of a file. This uses one of the F_*LCK flags.

INT2NUM(F_SETLK)

F_SETLKW =

Acquire a lock on a region of a file, waiting if necessary. This uses one of the F_*LCK flags

INT2NUM(F_SETLKW)

FD_CLOEXEC =

the value of the close-on-exec flag.

INT2NUM(FD_CLOEXEC)

F_RDLCK =

Read lock for a region of a file

INT2NUM(F_RDLCK)

F_UNLCK =

Remove lock for a region of a file

INT2NUM(F_UNLCK)

F_WRLCK =

Write lock for a region of a file

INT2NUM(F_WRLCK)

F_SETPIPE_SZ =

Change the capacity of the pipe referred to by fd to be at least arg bytes.

INT2NUM(F_SETPIPE_SZ)

F_GETPIPE_SZ =

Return (as the function result) the capacity of the pipe referred to by fd.

INT2NUM(F_GETPIPE_SZ)

O_CREAT =

Create the file if it doesn’t exist

INT2NUM(O_CREAT)

O_EXCL =

Used with O_CREAT, fail if the file exists

INT2NUM(O_EXCL)

O_NOCTTY =

Open TTY without it becoming the controlling TTY

INT2NUM(O_NOCTTY)

O_TRUNC =

Truncate the file on open

INT2NUM(O_TRUNC)

O_APPEND =

Open the file in append mode

INT2NUM(O_APPEND)

O_NONBLOCK =

Open the file in non-blocking mode

INT2NUM(O_NONBLOCK)

O_NDELAY =

Open the file in non-blocking mode

INT2NUM(O_NDELAY)

O_RDONLY =

Open the file in read-only mode

INT2NUM(O_RDONLY)

O_RDWR =

Open the file in read-write mode

INT2NUM(O_RDWR)

O_WRONLY =

Open the file in write-only mode.

INT2NUM(O_WRONLY)

O_ACCMODE =

Mask to extract the read/write flags

INT2FIX(O_ACCMODE)

F_DUP2FD =

It is a FreeBSD specific constant and equivalent to dup2 call.

INT2NUM(F_DUP2FD)

F_DUP2FD_CLOEXEC =

It is a FreeBSD specific constant and acts similarly as F_DUP2FD but set the FD_CLOEXEC flag in addition.

INT2NUM(F_DUP2FD_CLOEXEC)