Use Addrinfo.getaddrinfo instead. This method is deprecated for the following reasons:
The 3rd element of the result is the address family of the first address. The address families of the rest of the addresses are not returned.
gethostbyname() may take a long time and it may block other threads. (GVL cannot be released since gethostbyname() is not thread safe.)
This method uses gethostbyname() function already removed from POSIX.
This method lookups host information by hostname.
TCPSocket.gethostbyname("localhost") #=> ["localhost", ["hal"], 2, "127.0.0.1"]
Returns the remote address as an array which contains address_family and unix_path.
Example
serv = UNIXServer.new("/tmp/sock") c = UNIXSocket.new("/tmp/sock") p c.peeraddr #=> ["AF_UNIX", "/tmp/sock"]
Closes self for both reading and writing.
Raises IOError if reading or writing is attempted.
Related: StringIO#close_read, StringIO#close_write.
Returns true if self is closed for both reading and writing, false otherwise.
Reads and returns the next character from the stream; see Character IO.
Pushes back (“unshifts”) a character or integer onto the stream; see Character IO.
Pushes back (“unshifts”) an 8-bit byte onto the stream; see Byte IO.
Reads and returns the next 8-bit byte from the stream; see Byte IO.
Reads and returns a line from the stream; assigns the return value to $_; see Line IO.
Returns a new Hash object whose entries are those for which the block returns a truthy value:
h = {foo: 0, bar: 1, baz: 2} h.select {|key, value| value < 2 } # => {foo: 0, bar: 1}
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.select # => #<Enumerator: {foo: 0, bar: 1, baz: 2}:select> e.each {|key, value| value < 2 } # => {foo: 0, bar: 1}
Returns self, whose entries are those for which the block returns a truthy value:
h = {foo: 0, bar: 1, baz: 2} h.select! {|key, value| value < 2 } => {foo: 0, bar: 1}
Returns nil if no entries were removed.
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.select! # => #<Enumerator: {foo: 0, bar: 1, baz: 2}:select!> e.each { |key, value| value < 2 } # => {foo: 0, bar: 1}
Returns a new Hash object with the each key-value pair inverted:
h = {foo: 0, bar: 1, baz: 2} h1 = h.invert h1 # => {0=>:foo, 1=>:bar, 2=>:baz}
Overwrites any repeated new keys: (see Entry Order):
h = {foo: 0, bar: 0, baz: 0} h.invert # => {0=>:baz}
Returns true if key is a key in self, otherwise false.
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
Returns a Hash whose keys are the ENV values, and whose values are the corresponding ENV names:
ENV.replace('foo' => '0', 'bar' => '1') ENV.invert # => {"1"=>"bar", "0"=>"foo"}
For a duplicate ENV value, overwrites the hash entry:
ENV.replace('foo' => '0', 'bar' => '0') ENV.invert # => {"0"=>"foo"}
Note that the order of the ENV processing is OS-dependent, which means that the order of overwriting is also OS-dependent. See About Ordering.
Returns true if there is an environment variable with the given name:
ENV.replace('foo' => '0', 'bar' => '1') ENV.include?('foo') # => true
Returns false if name is a valid String and there is no such environment variable:
ENV.include?('baz') # => false
Returns false if name is the empty String or is a String containing character '=':
ENV.include?('') # => false ENV.include?('=') # => false
Raises an exception if name is a String containing the NUL character "\0":
ENV.include?("\0") # Raises ArgumentError (bad environment variable name: contains null byte)
Raises an exception if name has an encoding that is not ASCII-compatible:
ENV.include?("\xa1\xa1".force_encoding(Encoding::UTF_16LE)) # Raises ArgumentError (bad environment variable name: ASCII incompatible encoding: UTF-16LE)
Raises an exception if name is not a String:
ENV.include?(Object.new) # TypeError (no implicit conversion of Object into String)
Raises TypeError, because ENV is a wrapper for the process-wide environment variables and a clone is useless. Use to_h to get a copy of ENV data as a hash.
Returns the next line from the current file in ARGF.
By default lines are assumed to be separated by $/; to use a different character as a separator, supply it as a String for the sep argument.
The optional limit argument specifies how many characters of each line to return. By default all characters are returned.
See IO.readlines for details about getline_args.
Reads the next character from ARGF and returns it as a String. Returns nil at the end of the stream.
ARGF treats the files named on the command line as a single file created by concatenating their contents. After returning the last character of the first file, it returns the first character of the second file, and so on.
For example:
$ echo "foo" > file $ ruby argf.rb file ARGF.getc #=> "f" ARGF.getc #=> "o" ARGF.getc #=> "o" ARGF.getc #=> "\n" ARGF.getc #=> nil ARGF.getc #=> nil
Gets the next 8-bit byte (0..255) from ARGF. Returns nil if called at the end of the stream.
For example:
$ echo "foo" > file $ ruby argf.rb file ARGF.getbyte #=> 102 ARGF.getbyte #=> 111 ARGF.getbyte #=> 111 ARGF.getbyte #=> 10 ARGF.getbyte #=> nil