# The [IO](IO) class is the basis for all input and
# output in Ruby. An I/O stream may be *duplexed* (that is,
# bidirectional), and so may use more than one native operating system
# stream.
#
# Many of the examples in this section use the
# [File](https://ruby-doc.org/core-2.6.3/File.html) class, the only
# standard subclass of [IO](IO). The two classes are
# closely associated. Like the
# [File](https://ruby-doc.org/core-2.6.3/File.html) class, the Socket
# library subclasses from [IO](IO) (such as TCPSocket
# or UDPSocket).
#
# The
# [Kernel\#open](https://ruby-doc.org/core-2.6.3/Kernel.html#method-i-open)
# method can create an [IO](IO) (or
# [File](https://ruby-doc.org/core-2.6.3/File.html) ) object for these
# types of arguments:
#
#   - A plain string represents a filename suitable for the underlying
#     operating system.
#
#   - A string starting with `"|"` indicates a subprocess. The remainder
#     of the string following the `"|"` is invoked as a process with
#     appropriate input/output channels connected to it.
#
#   - A string equal to `"|-"` will create another Ruby instance as a
#     subprocess.
#
# The [IO](IO) may be opened with different file modes
# (read-only, write-only) and encodings for proper conversion. See
# [::new](IO#method-c-new) for these options. See
# [Kernel\#open](https://ruby-doc.org/core-2.6.3/Kernel.html#method-i-open)
# for details of the various command formats described above.
#
# [::popen](IO#method-c-popen), the Open3 library, or
# Process\#spawn may also be used to communicate with subprocesses through
# an [IO](IO).
#
# Ruby will convert pathnames between different operating system
# conventions if possible. For instance, on a Windows system the filename
# `"/gumby/ruby/test.rb"` will be opened as `"\gumby\ruby\test.rb"` . When
# specifying a Windows-style filename in a Ruby string, remember to escape
# the backslashes:
#
# ```ruby
# "C:\\gumby\\ruby\\test.rb"
# ```
#
# Our examples here will use the Unix-style forward slashes;
# File::ALT\_SEPARATOR can be used to get the platform-specific separator
# character.
#
# The global constant [ARGF](https://ruby-doc.org/core-2.6.3/ARGF.html)
# (also accessible as `$<` ) provides an IO-like stream which allows
# access to all files mentioned on the command line (or STDIN if no files
# are mentioned).
# [ARGF\#path](https://ruby-doc.org/core-2.6.3/ARGF.html#method-i-path)
# and its alias
# [ARGF\#filename](https://ruby-doc.org/core-2.6.3/ARGF.html#method-i-filename)
# are provided to access the name of the file currently being read.
#
#
# The io/console extension provides methods for interacting with the
# console. The console can be accessed from IO.console or the standard
# input/output/error [IO](IO) objects.
#
# Requiring io/console adds the following methods:
#
#   - IO::console
#
#   - IO\#raw
#
#   - IO\#raw\!
#
#   - IO\#cooked
#
#   - IO\#cooked\!
#
#   - IO\#getch
#
#   - IO\#echo=
#
#   - IO\#echo?
#
#   - IO\#noecho
#
#   - IO\#winsize
#
#   - IO\#winsize=
#
#   - IO\#iflush
#
#   - IO\#ioflush
#
#   - IO\#oflush
#
# Example:
#
# ```ruby
# require 'io/console'
# rows, columns = $stdout.winsize
# puts "Your screen is #{columns} wide and #{rows} tall"
# ```
class IO < Object
  include File::Constants

  include Enumerable[String]

  # String Output---Writes *obj* to *ios*. *obj* will be converted to a string
  # using `to_s`.
  #
  #     $stdout << "Hello " << "world!\n"
  #
  # *produces:*
  #
  #     Hello world!
  #
  def <<: (_ToS obj) -> self

  # Announce an intention to access data from the current file in a specific
  # pattern. On platforms that do not support the *posix_fadvise(2)* system call,
  # this method is a no-op.
  #
  # *advice* is one of the following symbols:
  #
  # :normal
  # :   No advice to give; the default assumption for an open file.
  # :sequential
  # :   The data will be accessed sequentially with lower offsets read before
  #     higher ones.
  # :random
  # :   The data will be accessed in random order.
  # :willneed
  # :   The data will be accessed in the near future.
  # :dontneed
  # :   The data will not be accessed in the near future.
  # :noreuse
  # :   The data will only be accessed once.
  #
  #
  # The semantics of a piece of advice are platform-dependent. See *man 2
  # posix_fadvise* for details.
  #
  # "data" means the region of the current file that begins at *offset* and
  # extends for *len* bytes. If *len* is 0, the region ends at the last byte of
  # the file. By default, both *offset* and *len* are 0, meaning that the advice
  # applies to the entire file.
  #
  # If an error occurs, one of the following exceptions will be raised:
  #
  # IOError
  # :   The IO stream is closed.
  # Errno::EBADF
  # :   The file descriptor of the current file is invalid.
  # Errno::EINVAL
  # :   An invalid value for *advice* was given.
  # Errno::ESPIPE
  # :   The file descriptor of the current file refers to a FIFO or pipe. (Linux
  #     raises Errno::EINVAL in this case).
  # TypeError
  # :   Either *advice* was not a Symbol, or one of the other arguments was not an
  #     Integer.
  # RangeError
  # :   One of the arguments given was too big/small.
  #
  # This list is not exhaustive; other Errno
  # :   exceptions are also possible.
  #
  def advise: ((:normal | :sequential | :random | :willneed | :dontneed | :noreuse) advise, ?Integer offset, ?Integer len) -> nil

  # Sets auto-close flag.
  #
  #     f = open("/dev/null")
  #     IO.for_fd(f.fileno)
  #     # ...
  #     f.gets # may cause Errno::EBADF
  #
  #     f = open("/dev/null")
  #     IO.for_fd(f.fileno).autoclose = false
  #     # ...
  #     f.gets # won't cause Errno::EBADF
  #
  def autoclose=: (boolish) -> untyped

  # Returns `true` if the underlying file descriptor of *ios* will be closed
  # automatically at its finalization, otherwise `false`.
  #
  def autoclose?: () -> bool

  # Puts *ios* into binary mode. Once a stream is in binary mode, it cannot
  # be reset to nonbinary mode.
  #
  #   - newline conversion disabled
  #
  #   - encoding conversion disabled
  #
  #   - content is treated as ASCII-8BIT
  def binmode: () -> self

  # Returns `true` if *ios* is binmode.
  def binmode?: () -> bool

  # Closes *ios* and flushes any pending writes to the operating system. The
  # stream is unavailable for any further data operations; an `IOError` is
  # raised if such an attempt is made. I/O streams are automatically closed
  # when they are claimed by the garbage collector.
  #
  # If *ios* is opened by `IO.popen`, `close` sets `$?` .
  #
  # Calling this method on closed [IO](IO.downloaded.ruby_doc) object is
  # just ignored since Ruby 2.3.
  def close: () -> NilClass

  def close_on_exec=: (boolish) -> untyped

  # Returns `true` if *ios* will be closed on exec.
  #
  # ```ruby
  # f = open("/dev/null")
  # f.close_on_exec?                 #=> false
  # f.close_on_exec = true
  # f.close_on_exec?                 #=> true
  # f.close_on_exec = false
  # f.close_on_exec?                 #=> false
  # ```
  def close_on_exec?: () -> bool

  # Closes the read end of a duplex I/O stream (i.e., one that contains both
  # a read and a write stream, such as a pipe). Will raise an `IOError` if
  # the stream is not duplexed.
  #
  # ```ruby
  # f = IO.popen("/bin/sh","r+")
  # f.close_read
  # f.readlines
  # ```
  #
  # *produces:*
  #
  #     prog.rb:3:in `readlines': not opened for reading (IOError)
  #      from prog.rb:3
  #
  # Calling this method on closed [IO](IO.downloaded.ruby_doc) object is
  # just ignored since Ruby 2.3.
  def close_read: () -> NilClass

  # Closes the write end of a duplex I/O stream (i.e., one that contains
  # both a read and a write stream, such as a pipe). Will raise an `IOError`
  # if the stream is not duplexed.
  #
  # ```ruby
  # f = IO.popen("/bin/sh","r+")
  # f.close_write
  # f.print "nowhere"
  # ```
  #
  # *produces:*
  #
  #     prog.rb:3:in `write': not opened for writing (IOError)
  #      from prog.rb:3:in `print'
  #      from prog.rb:3
  #
  # Calling this method on closed [IO](IO.downloaded.ruby_doc) object is
  # just ignored since Ruby 2.3.
  def close_write: () -> NilClass

  # Returns `true` if *ios* is completely closed (for duplex streams, both
  # reader and writer), `false` otherwise.
  #
  # ```ruby
  # f = File.new("testfile")
  # f.close         #=> nil
  # f.closed?       #=> true
  # f = IO.popen("/bin/sh","r+")
  # f.close_write   #=> nil
  # f.closed?       #=> false
  # f.close_read    #=> nil
  # f.closed?       #=> true
  # ```
  def closed?: () -> bool

  def each: (?String sep, ?Integer limit) { (String arg0) -> untyped } -> self
          | (?String sep, ?Integer limit) -> ::Enumerator[String, self]

  def each_byte: () { (Integer arg0) -> untyped } -> self
               | () -> ::Enumerator[Integer, self]

  def each_char: () { (String arg0) -> untyped } -> self
               | () -> ::Enumerator[String, self]

  def each_codepoint: () { (Integer arg0) -> untyped } -> self
                    | () -> ::Enumerator[Integer, self]

  # Returns true if *ios* is at end of file that means there are no more
  # data to read. The stream must be opened for reading or an `IOError` will
  # be raised.
  #
  # ```ruby
  # f = File.new("testfile")
  # dummy = f.readlines
  # f.eof   #=> true
  # ```
  #
  # If *ios* is a stream such as pipe or socket, `IO#eof?` blocks until the
  # other end sends some data or closes it.
  #
  # ```ruby
  # r, w = IO.pipe
  # Thread.new { sleep 1; w.close }
  # r.eof?  #=> true after 1 second blocking
  #
  # r, w = IO.pipe
  # Thread.new { sleep 1; w.puts "a" }
  # r.eof?  #=> false after 1 second blocking
  #
  # r, w = IO.pipe
  # r.eof?  # blocks forever
  # ```
  #
  # Note that `IO#eof?` reads data to the input byte buffer. So `IO#sysread`
  # may not behave as you intend with `IO#eof?`, unless you call
  # `IO#rewind` first (which is not available for some streams).
  def eof: () -> bool

  def fcntl: (Integer integer_cmd, String | Integer arg) -> Integer

  # Immediately writes all buffered data in *ios* to disk.
  #
  # If the underlying operating system does not support *fdatasync(2)* ,
  # `IO#fsync` is called instead (which might raise a `NotImplementedError`
  # ).
  def fdatasync: () -> Integer?

  # Returns an integer representing the numeric file descriptor for *ios* .
  #
  # ```ruby
  # $stdin.fileno    #=> 0
  # $stdout.fileno   #=> 1
  # ```
  #
  #
  #
  # Also aliased as: [to\_i](IO.downloaded.ruby_doc#method-i-to_i)
  def fileno: () -> Integer

  # Flushes any buffered data within *ios* to the underlying operating
  # system (note that this is Ruby internal buffering only; the OS may
  # buffer the data as well).
  #
  # ```ruby
  # $stdout.print "no newline"
  # $stdout.flush
  # ```
  #
  # *produces:*
  #
  # ```ruby
  # no newline
  # ```
  def flush: () -> self

  # Immediately writes all buffered data in *ios* to disk. Note that `fsync`
  # differs from using `IO#sync=` . The latter ensures that data is flushed
  # from Ruby’s buffers, but does not guarantee that the underlying
  # operating system actually writes it to disk.
  #
  # `NotImplementedError` is raised if the underlying operating system does
  # not support *fsync(2)* .
  def fsync: () -> Integer?

  # Gets the next 8-bit byte (0..255) from *ios* . Returns `nil` if called
  # at end of file.
  #
  # ```ruby
  # f = File.new("testfile")
  # f.getbyte   #=> 84
  # f.getbyte   #=> 104
  # ```
  def getbyte: () -> Integer?

  # Reads a one-character string from *ios* . Returns `nil` if called at end
  # of file.
  #
  # ```ruby
  # f = File.new("testfile")
  # f.getc   #=> "h"
  # f.getc   #=> "e"
  # ```
  def getc: () -> String?

  def gets: (?String sep, ?Integer limit) -> String?

  def initialize: (Integer fd, ?Integer mode, ?Integer opt) -> void

  # Return a string describing this [IO](IO.downloaded.ruby_doc) object.
  def inspect: () -> String

  # Returns the [Encoding](https://ruby-doc.org/core-2.6.3/Encoding.html) of
  # the internal string if conversion is specified. Otherwise returns `nil`
  # .
  def internal_encoding: () -> Encoding

  def ioctl: (Integer integer_cmd, String | Integer arg) -> Integer

  # Returns `true` if *ios* is associated with a terminal device (tty),
  # `false` otherwise.
  #
  # ```ruby
  # File.new("testfile").isatty   #=> false
  # File.new("/dev/tty").isatty   #=> true
  # ```
  def isatty: () -> bool

  # Returns the current line number in *ios* . The stream must be opened for
  # reading. `lineno` counts the number of times
  # [gets](IO.downloaded.ruby_doc#method-i-gets) is called rather than the
  # number of newlines encountered. The two values will differ if
  # [gets](IO.downloaded.ruby_doc#method-i-gets) is called with a separator
  # other than newline.
  #
  # Methods that use `$/` like [each](IO.downloaded.ruby_doc#method-i-each)
  # , [lines](IO.downloaded.ruby_doc#method-i-lines) and
  # [readline](IO.downloaded.ruby_doc#method-i-readline) will also increment
  # `lineno` .
  #
  # See also the `$.` variable.
  #
  # ```ruby
  # f = File.new("testfile")
  # f.lineno   #=> 0
  # f.gets     #=> "This is line one\n"
  # f.lineno   #=> 1
  # f.gets     #=> "This is line two\n"
  # f.lineno   #=> 2
  # ```
  def lineno: () -> Integer

  def lineno=: (Integer arg0) -> Integer

  # Returns the process ID of a child process associated with *ios* . This
  # will be set by `IO.popen` .
  #
  # ```ruby
  # pipe = IO.popen("-")
  # if pipe
  #   $stderr.puts "In parent, child pid is #{pipe.pid}"
  # else
  #   $stderr.puts "In child, pid is #{$$}"
  # end
  # ```
  #
  # *produces:*
  #
  #     In child, pid is 26209
  #     In parent, child pid is 26209
  def pid: () -> Integer

  # Returns the current offset (in bytes) of *ios* .
  #
  # ```ruby
  # f = File.new("testfile")
  # f.pos    #=> 0
  # f.gets   #=> "This is line one\n"
  # f.pos    #=> 17
  # ```
  def pos: () -> Integer

  def pos=: (Integer arg0) -> Integer

  def print: (*untyped arg0) -> NilClass

  def printf: (String format_string, *untyped arg0) -> NilClass

  def putc: (Numeric | String arg0) -> untyped

  def puts: (*untyped arg0) -> NilClass

  # Reads *length* bytes from the I/O stream.
  #
  # *length* must be a non-negative integer or `nil`.
  #
  # If *length* is a positive integer, `read` tries to read *length* bytes without
  # any conversion (binary mode). It returns `nil` if an EOF is encountered before
  # anything can be read. Fewer than *length* bytes are returned if an EOF is
  # encountered during the read. In the case of an integer *length*, the resulting
  # string is always in ASCII-8BIT encoding.
  #
  # If *length* is omitted or is `nil`, it reads until EOF and the encoding
  # conversion is applied, if applicable. A string is returned even if EOF is
  # encountered before any data is read.
  #
  # If *length* is zero, it returns an empty string (`""`).
  #
  # If the optional *outbuf* argument is present, it must reference a String,
  # which will receive the data. The *outbuf* will contain only the received data
  # after the method call even if it is not empty at the beginning.
  #
  # When this method is called at end of file, it returns `nil` or `""`, depending
  # on *length*: `read`, `read(nil)`, and `read(0)` return `""`,
  # `read(*positive_integer*)` returns `nil`.
  #
  #     f = File.new("testfile")
  #     f.read(16)   #=> "This is line one"
  #
  #     # read whole file
  #     open("file") do |f|
  #       data = f.read   # This returns a string even if the file is empty.
  #       # ...
  #     end
  #
  #     # iterate over fixed length records
  #     open("fixed-record-file") do |f|
  #       while record = f.read(256)
  #         # ...
  #       end
  #     end
  #
  #     # iterate over variable length records,
  #     # each record is prefixed by its 32-bit length
  #     open("variable-record-file") do |f|
  #       while len = f.read(4)
  #         len = len.unpack("N")[0]   # 32-bit length
  #         record = f.read(len)       # This returns a string even if len is 0.
  #       end
  #     end
  #
  # Note that this method behaves like the fread() function in C. This means it
  # retries to invoke read(2) system calls to read data with the specified length
  # (or until EOF). This behavior is preserved even if *ios* is in non-blocking
  # mode. (This method is non-blocking flag insensitive as other methods.) If you
  # need the behavior like a single read(2) system call, consider #readpartial,
  # #read_nonblock, and #sysread.
  #
  def read: (?int? length, ?string outbuf) -> String?

  def read_nonblock: (int len, ?string buf, ?exception: true) -> String
                   | (int len, ?string buf, exception: false) -> (String | :wait_readable | nil)

  # Reads a byte as with `IO#getbyte`, but raises an `EOFError` on end of
  # file.
  def readbyte: () -> Integer

  # Reads a one-character string from *ios* . Raises an `EOFError` on end of
  # file.
  #
  # ```ruby
  # f = File.new("testfile")
  # f.readchar   #=> "h"
  # f.readchar   #=> "e"
  # ```
  def readchar: () -> String

  def readline: (?String sep, ?Integer limit) -> String

  def readlines: (?String sep, ?Integer limit) -> ::Array[String]

  # Reads at most *maxlen* bytes from the I/O stream. It blocks only if *ios* has
  # no data immediately available. It doesn't block if some data available.
  #
  # If the optional *outbuf* argument is present, it must reference a String,
  # which will receive the data. The *outbuf* will contain only the received data
  # after the method call even if it is not empty at the beginning.
  #
  # It raises EOFError on end of file.
  #
  # readpartial is designed for streams such as pipe, socket, tty, etc. It blocks
  # only when no data immediately available. This means that it blocks only when
  # following all conditions hold.
  # *   the byte buffer in the IO object is empty.
  # *   the content of the stream is empty.
  # *   the stream is not reached to EOF.
  #
  #
  # When readpartial blocks, it waits data or EOF on the stream. If some data is
  # reached, readpartial returns with the data. If EOF is reached, readpartial
  # raises EOFError.
  #
  # When readpartial doesn't blocks, it returns or raises immediately. If the byte
  # buffer is not empty, it returns the data in the buffer. Otherwise if the
  # stream has some content, it returns the data in the stream. Otherwise if the
  # stream is reached to EOF, it raises EOFError.
  #
  #     r, w = IO.pipe           #               buffer          pipe content
  #     w << "abc"               #               ""              "abc".
  #     r.readpartial(4096)      #=> "abc"       ""              ""
  #     r.readpartial(4096)      # blocks because buffer and pipe is empty.
  #
  #     r, w = IO.pipe           #               buffer          pipe content
  #     w << "abc"               #               ""              "abc"
  #     w.close                  #               ""              "abc" EOF
  #     r.readpartial(4096)      #=> "abc"       ""              EOF
  #     r.readpartial(4096)      # raises EOFError
  #
  #     r, w = IO.pipe           #               buffer          pipe content
  #     w << "abc\ndef\n"        #               ""              "abc\ndef\n"
  #     r.gets                   #=> "abc\n"     "def\n"         ""
  #     w << "ghi\n"             #               "def\n"         "ghi\n"
  #     r.readpartial(4096)      #=> "def\n"     ""              "ghi\n"
  #     r.readpartial(4096)      #=> "ghi\n"     ""              ""
  #
  # Note that readpartial behaves similar to sysread. The differences are:
  # *   If the byte buffer is not empty, read from the byte buffer instead of
  #     "sysread for buffered IO (IOError)".
  # *   It doesn't cause Errno::EWOULDBLOCK and Errno::EINTR.  When readpartial
  #     meets EWOULDBLOCK and EINTR by read system call, readpartial retry the
  #     system call.
  #
  #
  # The latter means that readpartial is nonblocking-flag insensitive. It blocks
  # on the situation IO#sysread causes Errno::EWOULDBLOCK as if the fd is blocking
  # mode.
  #
  def readpartial: (int maxlen, ?string outbuf) -> String

  def reopen: (IO other_IO_or_path) -> IO
            | (String other_IO_or_path, ?String mode_str) -> IO

  # Positions *ios* to the beginning of input, resetting `lineno` to zero.
  #
  # ```ruby
  # f = File.new("testfile")
  # f.readline   #=> "This is line one\n"
  # f.rewind     #=> 0
  # f.lineno     #=> 0
  # f.readline   #=> "This is line one\n"
  # ```
  #
  # Note that it cannot be used with streams such as pipes, ttys, and
  # sockets.
  def rewind: () -> Integer

  def seek: (Integer amount, ?Integer whence) -> Integer

  def set_encoding: (?String | Encoding ext_or_ext_int_enc) -> self
                  | (?String | Encoding ext_or_ext_int_enc, ?String | Encoding int_enc) -> self

  # Returns status information for *ios* as an object of type `File::Stat` .
  #
  # ```ruby
  # f = File.new("testfile")
  # s = f.stat
  # "%o" % s.mode   #=> "100644"
  # s.blksize       #=> 4096
  # s.atime         #=> Wed Apr 09 08:53:54 CDT 2003
  # ```
  def stat: () -> File::Stat

  # Returns the current “sync mode” of *ios* . When sync mode is true, all
  # output is immediately flushed to the underlying operating system and is
  # not buffered by Ruby internally. See also `IO#fsync` .
  #
  # ```ruby
  # f = File.new("testfile")
  # f.sync   #=> false
  # ```
  def sync: () -> bool

  def sync=: (boolish) -> untyped

  def sysread: (Integer maxlen, String outbuf) -> String

  def sysseek: (Integer amount, ?Integer whence) -> Integer

  def syswrite: (_ToS arg0) -> Integer

  # Returns the current offset (in bytes) of *ios* .
  #
  # ```ruby
  # f = File.new("testfile")
  # f.pos    #=> 0
  # f.gets   #=> "This is line one\n"
  # f.pos    #=> 17
  # ```
  def tell: () -> Integer

  # Returns *ios* .
  def to_io: () -> self

  # Returns `true` if *ios* is associated with a terminal device (tty),
  # `false` otherwise.
  #
  # ```ruby
  # File.new("testfile").isatty   #=> false
  # File.new("/dev/tty").isatty   #=> true
  # ```
  def tty?: () -> bool

  def ungetbyte: (String | Integer arg0) -> NilClass

  def ungetc: (String arg0) -> NilClass

  # Writes the given strings to *ios*. The stream must be opened for writing.
  # Arguments that are not a string will be converted to a string using `to_s`.
  # Returns the number of bytes written in total.
  #
  #     count = $stdout.write("This is", " a test\n")
  #     puts "That was #{count} bytes of data"
  #
  # *produces:*
  #
  #     This is a test
  #     That was 15 bytes of data
  #
  def write: (*_ToS string) -> Integer

  def write_nonblock: (_ToS s, ?exception: true) -> Integer
                    | (_ToS s, exception: false) -> (Integer | :wait_writable | nil)

  # Opens the file, optionally seeks to the given *offset*, then returns *length*
  # bytes (defaulting to the rest of the file). #binread ensures the file is
  # closed before returning.  The open mode would be `"rb:ASCII-8BIT"`.
  #
  #     IO.binread("testfile")           #=> "This is line one\nThis is line two\nThis is line three\nAnd so on...\n"
  #     IO.binread("testfile", 20)       #=> "This is line one\nThi"
  #     IO.binread("testfile", 20, 10)   #=> "ne one\nThis is line "
  #
  def self.binread: (String name, ?Integer length, ?Integer offset) -> String

  # Same as IO.write except opening the file in binary mode and ASCII-8BIT
  # encoding (`"wb:ASCII-8BIT"`).
  #
  def self.binwrite: (String name, _ToS string, ?Integer offset, ?mode: String mode) -> Integer

  # IO.copy_stream copies *src* to *dst*. *src* and *dst* is either a filename or
  # an IO-like object. IO-like object for *src* should have #readpartial or #read
  # method.  IO-like object for *dst* should have #write method. (Specialized
  # mechanisms, such as sendfile system call, may be used on appropriate
  # situation.)
  #
  # This method returns the number of bytes copied.
  #
  # If optional arguments are not given, the start position of the copy is the
  # beginning of the filename or the current file offset of the IO. The end
  # position of the copy is the end of file.
  #
  # If *copy_length* is given, No more than *copy_length* bytes are copied.
  #
  # If *src_offset* is given, it specifies the start position of the copy.
  #
  # When *src_offset* is specified and *src* is an IO, IO.copy_stream doesn't move
  # the current file offset.
  #
  def self.copy_stream: ((String | _Reader | _ReaderPartial) src, (String | _Writer) dst, ?Integer copy_length, ?Integer src_offset) -> Integer

  def self.popen: (*untyped args) -> untyped

  def self.read: (String name, ?Integer length, ?Integer offset, ?external_encoding: String external_encoding, ?internal_encoding: String internal_encoding, ?encoding: String encoding, ?textmode: untyped textmode, ?binmode: untyped binmode, ?autoclose: untyped autoclose, ?mode: String mode) -> String

  def self.readlines: (String name, ?String sep, ?Integer limit, ?external_encoding: String external_encoding, ?internal_encoding: String internal_encoding, ?encoding: String encoding, ?textmode: untyped textmode, ?binmode: untyped binmode, ?autoclose: untyped autoclose, ?mode: String mode) -> ::Array[String]

  def self.select: [X, Y, Z] (::Array[X & io]? read_array, ?::Array[Y & io]? write_array, ?::Array[Z & io]? error_array) -> [Array[X], Array[Y], Array[Z]]
                 | [X, Y, Z] (::Array[X & io]? read_array, ?::Array[Y & io]? write_array, ?::Array[Z & io]? error_array, Numeric? timeout) -> [Array[X], Array[Y], Array[Z]]?

  def self.sysopen: (String path, ?String mode, ?String perm) -> Integer

  def self.try_convert: (untyped arg0) -> IO?

  def self.write: (String name, _ToS arg0, ?Integer offset, ?external_encoding: String external_encoding, ?internal_encoding: String internal_encoding, ?encoding: String encoding, ?textmode: untyped textmode, ?binmode: untyped binmode, ?autoclose: untyped autoclose, ?mode: String mode) -> Integer

  def self.for_fd: (int fd, ?(string | int) mode, **untyped opt) -> instance

  alias self.open self.for_fd

  def self.open: [A] (int fd, ?(string | int) mode, **untyped opt) { (instance) -> A } -> A
               | ...

  def bytes: () { (Integer arg0) -> untyped } -> self
           | () -> ::Enumerator[Integer, self]

  def chars: () { (String arg0) -> untyped } -> self
           | () -> ::Enumerator[String, self]

  def codepoints: () { (Integer arg0) -> untyped } -> self
                | () -> ::Enumerator[Integer, self]

  def each_line: (?String sep, ?Integer limit) { (String arg0) -> untyped } -> self
               | (?String sep, ?Integer limit) -> ::Enumerator[String, self]

  # Returns true if *ios* is at end of file that means there are no more
  # data to read. The stream must be opened for reading or an `IOError` will
  # be raised.
  #
  # ```ruby
  # f = File.new("testfile")
  # dummy = f.readlines
  # f.eof   #=> true
  # ```
  #
  # If *ios* is a stream such as pipe or socket, `IO#eof?` blocks until the
  # other end sends some data or closes it.
  #
  # ```ruby
  # r, w = IO.pipe
  # Thread.new { sleep 1; w.close }
  # r.eof?  #=> true after 1 second blocking
  #
  # r, w = IO.pipe
  # Thread.new { sleep 1; w.puts "a" }
  # r.eof?  #=> false after 1 second blocking
  #
  # r, w = IO.pipe
  # r.eof?  # blocks forever
  # ```
  #
  # Note that `IO#eof?` reads data to the input byte buffer. So `IO#sysread`
  # may not behave as you intend with `IO#eof?`, unless you call
  # `IO#rewind` first (which is not available for some streams).
  def eof?: () -> bool

  def lines: (?String sep, ?Integer limit) { (String arg0) -> untyped } -> self
           | (?String sep, ?Integer limit) -> ::Enumerator[String, self]

  # Alias for: [fileno](IO.downloaded.ruby_doc#method-i-fileno)
  def to_i: () -> Integer
end

IO::APPEND: Integer

IO::BINARY: Integer

IO::CREAT: Integer

IO::DIRECT: Integer

IO::DSYNC: Integer

IO::EXCL: Integer

IO::FNM_CASEFOLD: Integer

IO::FNM_DOTMATCH: Integer

IO::FNM_EXTGLOB: Integer

IO::FNM_NOESCAPE: Integer

IO::FNM_PATHNAME: Integer

IO::FNM_SHORTNAME: Integer

IO::FNM_SYSCASE: Integer

IO::LOCK_EX: Integer

IO::LOCK_NB: Integer

IO::LOCK_SH: Integer

IO::LOCK_UN: Integer

IO::NOATIME: Integer

IO::NOCTTY: Integer

IO::NOFOLLOW: Integer

IO::NONBLOCK: Integer

IO::NULL: String

IO::RDONLY: Integer

IO::RDWR: Integer

IO::RSYNC: Integer

IO::SEEK_CUR: Integer

IO::SEEK_DATA: Integer

IO::SEEK_END: Integer

IO::SEEK_HOLE: Integer

IO::SEEK_SET: Integer

IO::SHARE_DELETE: Integer

IO::SYNC: Integer

IO::TMPFILE: Integer

IO::TRUNC: Integer

IO::WRONLY: Integer

class IO::EAGAINWaitReadable < Errno::EAGAIN
  include IO::WaitReadable
end

IO::EAGAINWaitReadable::Errno: Integer

class IO::EAGAINWaitWritable < Errno::EAGAIN
  include IO::WaitWritable
end

IO::EAGAINWaitWritable::Errno: Integer

class IO::EINPROGRESSWaitReadable < Errno::EINPROGRESS
  include IO::WaitReadable
end

IO::EINPROGRESSWaitReadable::Errno: Integer

class IO::EINPROGRESSWaitWritable < Errno::EINPROGRESS
  include IO::WaitWritable
end

IO::EINPROGRESSWaitWritable::Errno: Integer

module IO::WaitReadable
end

module IO::WaitWritable
end