Results for: "module_function"

Yields each environment variable name and its value as a 2-element Array, returning a Hash of the names and values for which the block returns a truthy value:

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
ENV.select { |name, value| name.start_with?('b') } # => {"bar"=>"1", "baz"=>"2"}
ENV.filter { |name, value| name.start_with?('b') } # => {"bar"=>"1", "baz"=>"2"}

Returns an Enumerator if no block given:

e = ENV.select # => #<Enumerator: {"bar"=>"1", "baz"=>"2", "foo"=>"0"}:select>
e.each { |name, value | name.start_with?('b') } # => {"bar"=>"1", "baz"=>"2"}
e = ENV.filter # => #<Enumerator: {"bar"=>"1", "baz"=>"2", "foo"=>"0"}:filter>
e.each { |name, value | name.start_with?('b') } # => {"bar"=>"1", "baz"=>"2"}

Yields each environment variable name and its value as a 2-element Array, deleting each entry for which the block returns false or nil, and returning ENV if any deletions made, or nil otherwise:

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
ENV.select! { |name, value| name.start_with?('b') } # => ENV
ENV # => {"bar"=>"1", "baz"=>"2"}
ENV.select! { |name, value| true } # => nil

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
ENV.filter! { |name, value| name.start_with?('b') } # => ENV
ENV # => {"bar"=>"1", "baz"=>"2"}
ENV.filter! { |name, value| true } # => nil

Returns an Enumerator if no block given:

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
e = ENV.select! # => #<Enumerator: {"bar"=>"1", "baz"=>"2"}:select!>
e.each { |name, value| name.start_with?('b') } # => ENV
ENV # => {"bar"=>"1", "baz"=>"2"}
e.each { |name, value| true } # => nil

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
e = ENV.filter! # => #<Enumerator: {"bar"=>"1", "baz"=>"2"}:filter!>
e.each { |name, value| name.start_with?('b') } # => ENV
ENV # => {"bar"=>"1", "baz"=>"2"}
e.each { |name, value| true } # => nil

Wait for any ractor to have something in its outgoing port, read from this ractor, and then return that ractor and the object received.

r1 = Ractor.new {Ractor.yield 'from 1'}
r2 = Ractor.new {Ractor.yield 'from 2'}

r, obj = Ractor.select(r1, r2)

puts "received #{obj.inspect} from #{r.inspect}"
# Prints: received "from 1" from #<Ractor:#2 test.rb:1 running>
# But could just as well print "from r2" here, either prints could be first.

If one of the given ractors is the current ractor, and it is selected, r will contain the :receive symbol instead of the ractor object.

r1 = Ractor.new(Ractor.current) do |main|
  main.send 'to main'
  Ractor.yield 'from 1'
end
r2 = Ractor.new do
  Ractor.yield 'from 2'
end

r, obj = Ractor.select(r1, r2, Ractor.current)
puts "received #{obj.inspect} from #{r.inspect}"
# Could print: received "to main" from :receive

If yield_value is provided, that value may be yielded if another ractor is calling take. In this case, the pair [:yield, nil] is returned:

r1 = Ractor.new(Ractor.current) do |main|
  puts "Received from main: #{main.take}"
end

puts "Trying to select"
r, obj = Ractor.select(r1, Ractor.current, yield_value: 123)
wait
puts "Received #{obj.inspect} from #{r.inspect}"

This will print:

Trying to select
Received from main: 123
Received nil from :yield

move boolean flag defines whether yielded value will be copied (default) or moved.

Invokes system call select(2), which monitors multiple file descriptors, waiting until one or more of the file descriptors becomes ready for some class of I/O operation.

Not implemented on all platforms.

Each of the arguments read_ios, write_ios, and error_ios is an array of IO objects.

Argument timeout is an integer timeout interval in seconds.

The method monitors the IO objects given in all three arrays, waiting for some to be ready; returns a 3-element array whose elements are:

• An array of the objects in read_ios that are ready for reading.

• An array of the objects in write_ios that are ready for writing.

• An array of the objects in error_ios have pending exceptions.

If no object becomes ready within the given timeout, nil is returned.

IO.select peeks the buffer of IO objects for testing readability. If the IO buffer is not empty, IO.select immediately notifies readability. This “peek” only happens for IO objects. It does not happen for IO-like objects such as OpenSSL::SSL::SSLSocket.

The best way to use IO.select is invoking it after non-blocking methods such as read_nonblock, write_nonblock, etc. The methods raise an exception which is extended by IO::WaitReadable or IO::WaitWritable. The modules notify how the caller should wait with IO.select. If IO::WaitReadable is raised, the caller should wait for reading. If IO::WaitWritable is raised, the caller should wait for writing.

So, blocking read (readpartial) can be emulated using read_nonblock and IO.select as follows:

begin
  result = io_like.read_nonblock(maxlen)
rescue IO::WaitReadable
  IO.select([io_like])
  retry
rescue IO::WaitWritable
  IO.select(nil, [io_like])
  retry
end

Especially, the combination of non-blocking methods and IO.select is preferred for IO like objects such as OpenSSL::SSL::SSLSocket. It has to_io method to return underlying IO object. IO.select calls to_io to obtain the file descriptor to wait.

This means that readability notified by IO.select doesn’t mean readability from OpenSSL::SSL::SSLSocket object.

The most likely situation is that OpenSSL::SSL::SSLSocket buffers some data. IO.select doesn’t see the buffer. So IO.select can block when OpenSSL::SSL::SSLSocket#readpartial doesn’t block.

However, several more complicated situations exist.

SSL is a protocol which is sequence of records. The record consists of multiple bytes. So, the remote side of SSL sends a partial record, IO.select notifies readability but OpenSSL::SSL::SSLSocket cannot decrypt a byte and OpenSSL::SSL::SSLSocket#readpartial will block.

Also, the remote side can request SSL renegotiation which forces the local SSL engine to write some data. This means OpenSSL::SSL::SSLSocket#readpartial may invoke write system call and it can block. In such a situation, OpenSSL::SSL::SSLSocket#read_nonblock raises IO::WaitWritable instead of blocking. So, the caller should wait for ready for writability as above example.

The combination of non-blocking methods and IO.select is also useful for streams such as tty, pipe socket socket when multiple processes read from a stream.

Finally, Linux kernel developers don’t guarantee that readability of select(2) means readability of following read(2) even for a single process; see select(2)

Invoking IO.select before IO#readpartial works well as usual. However it is not the best way to use IO.select.

The writability notified by select(2) doesn’t show how many bytes are writable. IO#write method blocks until given whole string is written. So, IO#write(two or more bytes) can block after writability is notified by IO.select. IO#write_nonblock is required to avoid the blocking.

Blocking write (write) can be emulated using write_nonblock and IO.select as follows: IO::WaitReadable should also be rescued for SSL renegotiation in OpenSSL::SSL::SSLSocket.

while 0 < string.bytesize
  begin
    written = io_like.write_nonblock(string)
  rescue IO::WaitReadable
    IO.select([io_like])
    retry
  rescue IO::WaitWritable
    IO.select(nil, [io_like])
    retry
  end
  string = string.byteslice(written..-1)
end

Example:

rp, wp = IO.pipe
mesg = "ping "
100.times {
  # IO.select follows IO#read.  Not the best way to use IO.select.
  rs, ws, = IO.select([rp], [wp])
  if r = rs[0]
    ret = r.read(5)
    print ret
    case ret
    when /ping/
      mesg = "pong\n"
    when /pong/
      mesg = "ping "
    end
  end
  if w = ws[0]
    w.write(mesg)
  end
}

Output:

ping pong
ping pong
ping pong
(snipped)
ping

Returns an array containing elements selected by the block.

With a block given, calls the block with successive elements; returns an array of those elements for which the block returns a truthy value:

(0..9).select {|element| element % 3 == 0 } # => [0, 3, 6, 9]
a = {foo: 0, bar: 1, baz: 2}.select {|key, value| key.start_with?('b') }
a # => {:bar=>1, :baz=>2}

With no block given, returns an Enumerator.

Related: reject.

Returns an array of objects returned by the block.

With a block given, calls the block with successive elements; returns an array of the objects returned by the block:

(0..4).map {|i| i*i }                               # => [0, 1, 4, 9, 16]
{foo: 0, bar: 1, baz: 2}.map {|key, value| value*2} # => [0, 2, 4]

With no block given, returns an Enumerator.

Generates a hex-encoded version of a given string.

Detaches the current process from its controlling terminal and runs it in the background as system daemon; returns zero.

By default:

• Changes the current working directory to the root directory.

• Redirects $stdin, $stdout, and $stderr to the null device.

If optional argument nochdir is true, does not change the current working directory.

If optional argument noclose is true, does not redirect $stdin, $stdout, or $stderr.

Takes a token and gets the next token in the Negotiate authentication chain. Token can be Base64 encoded or not. The token can include the “Negotiate” header and it will be stripped. Does not indicate if SEC_I_CONTINUE or SEC_E_OK was returned. Token returned is Base64 encoded w/ all new lines removed.

Return the value that should be dumped for the command_line option.

returns an integer in (-infty, 0] a number closer to 0 means the dependency is less constraining

dependencies w/ 0 or 1 possibilities (ignoring version requirements) are given very negative values, so they always sort first, before dependencies that are unconstrained

Invoked by IO.select to ask whether the specified descriptors are ready for specified events within the specified timeout.

Expected to return the 3-tuple of Array of IOs that are ready.

Returns a list of encodings in Content-Encoding field as an array of strings.

The encodings are downcased for canonicalization.

Returns reference counter of Dispatch interface of WIN32OLE object. You should not use this method because this method exists only for debugging WIN32OLE.

Counts objects for each T_IMEMO type.

This method is only for MRI developers interested in performance and memory usage of Ruby programs.

It returns a hash as:

{:imemo_ifunc=>8,
 :imemo_svar=>7,
 :imemo_cref=>509,
 :imemo_memo=>1,
 :imemo_throw_data=>1}

If the optional argument, result_hash, is given, it is overwritten and returned. This is intended to avoid probe effect.

The contents of the returned hash is implementation specific and may change in the future.

In this version, keys are symbol objects.

This method is only expected to work with C Ruby.

Like URI.encode_www_form_component, except that ' ' (space) is encoded as '%20' (instead of '+').

Compile a RegularExpressionNode node

Dispatch enter and leave events for RegularExpressionNode nodes and continue walking the tree.

Inspect a RegularExpressionNode node.