In the first form, returns an array of the names of all constants accessible from the point of call. This list includes the names of all modules and classes defined in the global scope.
Module.constants.first(4) # => [:ARGF, :ARGV, :ArgumentError, :Array] Module.constants.include?(:SEEK_SET) # => false class IO Module.constants.include?(:SEEK_SET) # => true end
The second form calls the instance method constants.
Returns a list of modules included/prepended in mod (including mod itself).
module Mod include Math include Comparable prepend Enumerable end Mod.ancestors #=> [Enumerable, Mod, Comparable, Math] Math.ancestors #=> [Math] Enumerable.ancestors #=> [Enumerable]
The first form is equivalent to attr_reader. The second form is equivalent to attr_accessor(name) but deprecated. The last form is equivalent to attr_reader(name) but deprecated. Returns an array of defined method names as symbols.
Returns an array of the names of the constants accessible in mod. This includes the names of constants in any included modules (example at start of section), unless the inherit parameter is set to false.
The implementation makes no guarantees about the order in which the constants are yielded.
IO.constants.include?(:SYNC) #=> true IO.constants(false).include?(:SYNC) #=> false
Also see Module#const_defined?.
With no arguments, sets the default visibility for subsequently defined methods to private. With arguments, sets the named methods to have private visibility. String arguments are converted to symbols. An Array of Symbols and/or Strings is also accepted. If a single argument is passed, it is returned. If no argument is passed, nil is returned. If multiple arguments are passed, the arguments are returned as an array.
module Mod def a() end def b() end private def c() end private :a end Mod.private_instance_methods #=> [:a, :c]
Note that to show a private method on RDoc, use :doc:.
Returns true if self is a Friday, false otherwise.
Returns true if the date is on or after the date of calendar reform, false otherwise:
Date.new(1582, 10, 15).gregorian? # => true (Date.new(1582, 10, 15) - 1).gregorian? # => false
Returns the Julian start date for calendar reform; if not an infinity, the returned value is suitable for passing to Date#jd:
d = Date.new(2001, 2, 3, Date::ITALY) s = d.start # => 2299161.0 Date.jd(s).to_s # => "1582-10-15" d = Date.new(2001, 2, 3, Date::ENGLAND) s = d.start # => 2361222.0 Date.jd(s).to_s # => "1752-09-14" Date.new(2001, 2, 3, Date::GREGORIAN).start # => -Infinity Date.new(2001, 2, 3, Date::JULIAN).start # => Infinity
See argument start.
Equivalent to Date#new_start with argument Date::GREGORIAN.
Calls the block with specified dates; returns self.
The first date is self.
Each successive date is date + step, where step is the numeric step size in days.
The last date is the last one that is before or equal to limit, which should be a Date object.
Example:
limit = Date.new(2001, 12, 31) Date.new(2001).step(limit){|date| p date.to_s if date.mday == 31 }
Output:
"2001-01-31" "2001-03-31" "2001-05-31" "2001-07-31" "2001-08-31" "2001-10-31" "2001-12-31"
Returns an Enumerator if no block is given.
Returns true if self is in daylight saving time, false otherwise:
t = Time.local(2000, 1, 1) # => 2000-01-01 00:00:00 -0600 t.zone # => "Central Standard Time" t.dst? # => false t = Time.local(2000, 7, 1) # => 2000-07-01 00:00:00 -0500 t.zone # => "Central Daylight Time" t.dst? # => true
Returns true if self is in daylight saving time, false otherwise:
t = Time.local(2000, 1, 1) # => 2000-01-01 00:00:00 -0600 t.zone # => "Central Standard Time" t.dst? # => false t = Time.local(2000, 7, 1) # => 2000-07-01 00:00:00 -0500 t.zone # => "Central Daylight Time" t.dst? # => true
Returns true if self represents a Friday, false otherwise:
t = Time.utc(2000, 1, 7) # => 2000-01-07 00:00:00 UTC t.friday? # => true
Related: Time#saturday?, Time#sunday?, Time#monday?.
Returns status information for ios as an object of type File::Stat.
f = File.new("testfile") s = f.stat "%o" % s.mode #=> "100644" s.blksize #=> 4096 s.atime #=> Wed Apr 09 08:53:54 CDT 2003
Opens the stream, writes the given data to it, and closes the stream; returns the number of bytes written.
When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.
The first argument must be a string that is the path to a file.
With only argument path given, writes the given data to the file at that path:
IO.write('t.tmp', 'abc') # => 3 File.read('t.tmp') # => "abc"
If offset is zero (the default), the file is overwritten:
IO.write('t.tmp', 'A') # => 1 File.read('t.tmp') # => "A"
If offset in within the file content, the file is partly overwritten:
IO.write('t.tmp', 'abcdef') # => 3 File.read('t.tmp') # => "abcdef" # Offset within content. IO.write('t.tmp', '012', 2) # => 3 File.read('t.tmp') # => "ab012f"
If offset is outside the file content, the file is padded with null characters "\u0000":
IO.write('t.tmp', 'xyz', 10) # => 3 File.read('t.tmp') # => "ab012f\u0000\u0000\u0000\u0000xyz"
Optional keyword arguments opts specify:
Encoding options.
Behaves like IO.write, except that the stream is opened in binary mode with ASCII-8BIT encoding.
When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.
Creates a pair of pipe endpoints, read_io and write_io, connected to each other.
If argument enc_string is given, it must be a string containing one of:
The name of the encoding to be used as the external encoding.
The colon-separated names of two encodings to be used as the external and internal encodings.
If argument int_enc is given, it must be an Encoding object or encoding name string that specifies the internal encoding to be used; if argument ext_enc is also given, it must be an Encoding object or encoding name string that specifies the external encoding to be used.
The string read from read_io is tagged with the external encoding; if an internal encoding is also specified, the string is converted to, and tagged with, that encoding.
If any encoding is specified, optional hash arguments specify the conversion option.
Optional keyword arguments opts specify:
Encoding Options.
With no block given, returns the two endpoints in an array:
IO.pipe # => [#<IO:fd 4>, #<IO:fd 5>]
With a block given, calls the block with the two endpoints; closes both endpoints and returns the value of the block:
IO.pipe {|read_io, write_io| p read_io; p write_io }
Output:
#<IO:fd 6> #<IO:fd 7>
Not available on all platforms.
In the example below, the two processes close the ends of the pipe that they are not using. This is not just a cosmetic nicety. The read end of a pipe will not generate an end of file condition if there are any writers with the pipe still open. In the case of the parent process, the rd.read will never return if it does not first issue a wr.close:
rd, wr = IO.pipe if fork wr.close puts "Parent got: <#{rd.read}>" rd.close Process.wait else rd.close puts 'Sending message to parent' wr.write "Hi Dad" wr.close end
produces:
Sending message to parent Parent got: <Hi Dad>
Writes the given objects to the stream; returns nil. Appends the output record separator $OUTPUT_RECORD_SEPARATOR ($\), if it is not nil. See Line IO.
With argument objects given, for each object:
Converts via its method to_s if not a string.
Writes to the stream.
If not the last object, writes the output field separator $OUTPUT_FIELD_SEPARATOR ($,) if it is not nil.
With default separators:
f = File.open('t.tmp', 'w+') objects = [0, 0.0, Rational(0, 1), Complex(0, 0), :zero, 'zero'] p $OUTPUT_RECORD_SEPARATOR p $OUTPUT_FIELD_SEPARATOR f.print(*objects) f.rewind p f.read f.close
Output:
nil nil "00.00/10+0izerozero"
With specified separators:
$\ = "\n" $, = ',' f.rewind f.print(*objects) f.rewind p f.read
Output:
"0,0.0,0/1,0+0i,zero,zero\n"
With no argument given, writes the content of $_ (which is usually the most recent user input):
f = File.open('t.tmp', 'w+') gets # Sets $_ to the most recent user input. f.print f.close
Formats and writes objects to the stream.
For details on format_string, see Format Specifications.
Writes the given object to self, which must be opened for writing (see Modes); returns the number bytes written. If object is not a string is converted via method to_s:
f = File.new('t.tmp', 'w') f.syswrite('foo') # => 3 f.syswrite(30) # => 2 f.syswrite(:foo) # => 3 f.close
This methods should not be used with other stream-writer methods.
Behaves like IO#write, except that it:
Writes at the given offset (in bytes).
Disregards, and does not modify, the stream’s position (see Position).
Bypasses any user space buffering in the stream.
Because this method does not disturb the stream’s state (its position, in particular), pwrite allows multiple threads and processes to use the same IO object for writing at various offsets.
f = File.open('t.tmp', 'w+') # Write 6 bytes at offset 3. f.pwrite('ABCDEF', 3) # => 6 f.rewind f.read # => "\u0000\u0000\u0000ABCDEF" f.close
Not available on some platforms.
Writes each of the given objects to self, which must be opened for writing (see Access Modes); returns the total number bytes written; each of objects that is not a string is converted via method to_s:
$stdout.write('Hello', ', ', 'World!', "\n") # => 14 $stdout.write('foo', :bar, 2, "\n") # => 8
Output:
Hello, World! foobar2
Related: IO#read.
Iterates over the elements of range in steps of s. The iteration is performed by + operator:
(0..6).step(2) { puts _1 } #=> 1..5 # Prints: 0, 2, 4, 6 # Iterate between two dates in step of 1 day (24 hours) (Time.utc(2022, 2, 24)..Time.utc(2022, 3, 1)).step(24*60*60) { puts _1 } # Prints: # 2022-02-24 00:00:00 UTC # 2022-02-25 00:00:00 UTC # 2022-02-26 00:00:00 UTC # 2022-02-27 00:00:00 UTC # 2022-02-28 00:00:00 UTC # 2022-03-01 00:00:00 UTC
If + step decreases the value, iteration is still performed when step begin is higher than the end:
(0..6).step(-2) { puts _1 } # Prints nothing (6..0).step(-2) { puts _1 } # Prints: 6, 4, 2, 0 (Time.utc(2022, 3, 1)..Time.utc(2022, 2, 24)).step(-24*60*60) { puts _1 } # Prints: # 2022-03-01 00:00:00 UTC # 2022-02-28 00:00:00 UTC # 2022-02-27 00:00:00 UTC # 2022-02-26 00:00:00 UTC # 2022-02-25 00:00:00 UTC # 2022-02-24 00:00:00 UTC
When the block is not provided, and range boundaries and step are Numeric, the method returns Enumerator::ArithmeticSequence.
(1..5).step(2) # => ((1..5).step(2)) (1.0..).step(1.5) #=> ((1.0..).step(1.5)) (..3r).step(1/3r) #=> ((..3/1).step((1/3)))
Enumerator::ArithmeticSequence can be further used as a value object for iteration or slicing of collections (see Array#[]). There is a convenience method % with behavior similar to step to produce arithmetic sequences more expressively:
# Same as (1..5).step(2) (1..5) % 2 # => ((1..5).%(2))
In a generic case, when the block is not provided, Enumerator is returned:
('a'..).step('b') #=> #<Enumerator: "a"..:step("b")> ('a'..).step('b').take(3) #=> ["a", "ab", "abb"]
If s is not provided, it is considered 1 for ranges with numeric begin:
(1..5).step { p _1 } # Prints: 1, 2, 3, 4, 5
For non-Numeric ranges, step absence is an error:
(Time.utc(2022, 3, 1)..Time.utc(2022, 2, 24)).step { p _1 } # raises: step is required for non-numeric ranges (ArgumentError)
For backward compatibility reasons, String ranges support the iteration both with string step and with integer step. In the latter case, the iteration is performed by calculating the next values with String#succ:
('a'..'e').step(2) { p _1 } # Prints: a, c, e ('a'..'e').step { p _1 } # Default step 1; prints: a, b, c, d, e
With no argument, returns the first element of self, if it exists:
(1..4).first # => 1 ('a'..'d').first # => "a"
With non-negative integer argument n given, returns the first n elements in an array:
(1..10).first(3) # => [1, 2, 3] (1..10).first(0) # => [] (1..4).first(50) # => [1, 2, 3, 4]
Raises an exception if there is no first element:
(..4).first # Raises RangeError
With no argument, returns the last element of self, if it exists:
(1..4).last # => 4 ('a'..'d').last # => "d"
Note that last with no argument returns the end element of self even if exclude_end? is true:
(1...4).last # => 4 ('a'...'d').last # => "d"
With non-negative integer argument n given, returns the last n elements in an array:
(1..10).last(3) # => [8, 9, 10] (1..10).last(0) # => [] (1..4).last(50) # => [1, 2, 3, 4]
Note that last with argument does not return the end element of self if exclude_end? it true:
(1...4).last(3) # => [1, 2, 3] ('a'...'d').last(3) # => ["a", "b", "c"]
Raises an exception if there is no last element:
(1..).last # Raises RangeError