Returns a Digest subclass by name in a thread-safe manner even when on-demand loading is involved.
require 'digest' Digest("MD5") # => Digest::MD5 Digest(:SHA256) # => Digest::SHA256 Digest(:Foo) # => LoadError: library not found for class Digest::Foo -- digest/foo
Returns any backtrace associated with the exception. The backtrace is an array of strings, each containing either “filename:lineNo: in ‘method”’ or “filename:lineNo.”
def a raise "boom" end def b a() end begin b() rescue => detail print detail.backtrace.join("\n") end
produces:
prog.rb:2:in `a' prog.rb:6:in `b' prog.rb:10
Return the status value associated with this system exit.
Returns the list of Modules nested at the point of call.
module M1 module M2 $a = Module.nesting end end $a #=> [M1::M2, M1] $a[0].name #=> "M1::M2"
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]
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.
module Mod def a() end def b() end private def c() end private :a end Mod.private_instance_methods #=> [:a, :c]
Truncate to the nearest integer (by default), returning the result as a BigDecimal.
BigDecimal('3.14159').truncate #=> 3 BigDecimal('8.7').truncate #=> 8 BigDecimal('-9.9').truncate #=> -9
If n is specified and positive, the fractional part of the result has no more than that many digits.
If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.
BigDecimal('3.14159').truncate(3) #=> 3.141 BigDecimal('13345.234').truncate(-2) #=> 13300.0
Returns true if self is a prime number, else returns false.
As int is already an Integer, all these methods simply return the receiver.
Returns the truncated value (toward zero).
Rational(3).truncate #=> 3 Rational(2, 3).truncate #=> 0 Rational(-3, 2).truncate #=> -1 # decimal - 1 2 3 . 4 5 6 # ^ ^ ^ ^ ^ ^ # precision -3 -2 -1 0 +1 +2 '%f' % Rational('-123.456').truncate(+1) #=> "-123.400000" '%f' % Rational('-123.456').truncate(-1) #=> "-120.000000"
Returns true if the date is Friday.
Retunrs true if the date is on or after the day of calendar reform.
Date.new(1582,10,15).gregorian? #=> true (Date.new(1582,10,15) - 1).gregorian? #=> false
Returns the Julian day number denoting the day of calendar reform.
Date.new(2001,2,3).start #=> 2299161.0 Date.new(2001,2,3,Date::GREGORIAN).start #=> -Infinity
This method is equivalent to new_start(Date::GREGORIAN).
Iterates evaluation of the given block, which takes a date object. The limit should be a date object.
Date.new(2001).step(Date.new(2001,-1,-1)).select{|d| d.sunday?}.size #=> 52
Returns true if time occurs during Daylight Saving Time in its time zone.
# CST6CDT: Time.local(2000, 1, 1).zone #=> "CST" Time.local(2000, 1, 1).isdst #=> false Time.local(2000, 1, 1).dst? #=> false Time.local(2000, 7, 1).zone #=> "CDT" Time.local(2000, 7, 1).isdst #=> true Time.local(2000, 7, 1).dst? #=> true # Asia/Tokyo: Time.local(2000, 1, 1).zone #=> "JST" Time.local(2000, 1, 1).isdst #=> false Time.local(2000, 1, 1).dst? #=> false Time.local(2000, 7, 1).zone #=> "JST" Time.local(2000, 7, 1).isdst #=> false Time.local(2000, 7, 1).dst? #=> false
Returns true if time occurs during Daylight Saving Time in its time zone.
# CST6CDT: Time.local(2000, 1, 1).zone #=> "CST" Time.local(2000, 1, 1).isdst #=> false Time.local(2000, 1, 1).dst? #=> false Time.local(2000, 7, 1).zone #=> "CDT" Time.local(2000, 7, 1).isdst #=> true Time.local(2000, 7, 1).dst? #=> true # Asia/Tokyo: Time.local(2000, 1, 1).zone #=> "JST" Time.local(2000, 1, 1).isdst #=> false Time.local(2000, 1, 1).dst? #=> false Time.local(2000, 7, 1).zone #=> "JST" Time.local(2000, 7, 1).isdst #=> false Time.local(2000, 7, 1).dst? #=> false
Returns true if time represents Friday.
t = Time.local(1987, 12, 18) #=> 1987-12-18 00:00:00 -0600 t.friday? #=> true
Stores the specified string value in the database, indexed via the string key provided.
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 file, optionally seeks to the given offset, writes string, then returns the length written. write ensures the file is closed before returning. If offset is not given in write mode, the file is truncated. Otherwise, it is not truncated.
If the last argument is a hash, it specifies option for internal open(). The key would be the following. open_args: is exclusive to others.
encoding: string or encoding
specifies encoding of the read string. encoding will be ignored
if length is specified.
mode: string
specifies mode argument for open(). it should start with "w" or "a" or "r+"
otherwise it would cause error.
perm: fixnum
specifies perm argument for open().
open_args: array
specifies arguments for open() as an array.
IO.write("testfile", "0123456789", 20) # => 10
# File could contain: "This is line one\nThi0123456789two\nThis is line three\nAnd so on...\n"
IO.write("testfile", "0123456789") #=> 10
# File would now read: "0123456789"
Same as IO.write except opening the file in binary mode and ASCII-8BIT encoding (“wb:ASCII-8BIT”).