new(*args) public

Returns a new IO object (a stream) for the given IO object or integer file descriptor and mode string. See also IO#fileno and IO.for_fd.

Parameters

fd

numeric file descriptor

mode

file mode. a string or an integer

opt

hash for specifiying mode by name.

Mode

When mode is an integer it must be combination of the modes defined in File::Constants.

When mode is a string it must be in one of the following forms:

  • “fmode”,

  • “fmode:extern”,

  • “fmode:extern:intern”.

extern is the external encoding name for the IO. intern is the internal encoding. fmode must be combination of the directives. See the description of class IO for a description of the directives.

Options

opt can have the following keys

:mode

same as mode parameter

:external_encoding

external encoding for the IO. “-” is a synonym for the default external encoding.

:internal_encoding

internal encoding for the IO. “-” is a synonym for the default internal encoding. If the value is nil no conversion occurs.

:encoding

specifies external and internal encodings as “extern:intern”.

:textmode

If the value is truth value, same as “b” in argument mode.

:binmode

If the value is truth value, same as “t” in argument mode.

Also opt can have same keys in String#encode for controlling conversion between the external encoding and the internal encoding.

Example1

a = IO.new(2,"w")      # '2' is standard error
$stderr.puts "Hello"
a.puts "World"

produces:

Hello
World

Example2

io = IO.new(2, mode: 'w:UTF-16LE', cr_newline: true)
io.puts "Hello, World!"

io = IO.new(2, mode: 'w', cr_newline: true, external_encoding: Encoding::UTF_16LE)
io.puts "Hello, World!"

both of aboves print “Hello, World!” in UTF-16LE to standard error output with converting EOL generated by puts to CR.

Show source
Register or log in to add new notes.