Ruby/Справочник/Kernel
Примесь Kernel
[править]Since Ruby is very dynamic, methods added to the ancestors of BlankSlate after BlankSlate is defined will show up in the list of available BlankSlate methods. We handle this by defining a hook in the Object and Kernel classes that will hide any defined
Some objects are dupable, some are not. So we define a version of dup (called rake_dup) that returns self on the handful of classes that are not dupable.
Create a global fork method
Методы объекта
Array, Float, Integer, Pathname, String, URI, `, abort, at_exit, autoload?, autoload, binding, block_given?, callcc, caller, catch, chomp!, chomp, chop!, chop, eval, exec, exit!, exit, fail, fork, format, gem, getc, gets, global_variables, gsub!, gsub, iterator?, lambda, load, local_variables, loop, method_missing, open_uri_original_open, open, pp, pretty_inspect, printf, print, proc, putc, puts, p, raise, rake_dup, rand, readlines, readline, require_gem, require, scanf, scan, select, set_trace_func, sleep, split, sprintf, srand, sub!, sub, syscall, system, test, throw, to_ptr, trace_var, trap, untrace_var, warn, y
Kernel#Array
[править]Array(arg) => array
Returns arg as an Array. First tries to call arg.to_ary, then arg.to_a. If both fail, creates a single element array containing arg (unless arg is nil).
Array(1..5) #=> [1, 2, 3, 4, 5]
Kernel#Float
[править]Float(arg) => float
Returns arg converted to a float. Numeric types are converted directly, the rest are converted using arg.to_f. As of Ruby 1.8, converting nil generates a TypeError.
Float(1) #=> 1.0
Float("123.456") #=> 123.456
Kernel#Integer
[править]Integer(arg) => integer
Converts arg to a Fixnum or Bignum. Numeric types are converted directly (with floating point numbers being truncated). If arg is a String, leading radix indicators (0, 0b, and 0x) are honored. Others are converted using to_int and to_i. This behavior is different from that of String#to_i.
Integer(123.999) #=> 123
Integer("0x1a") #=> 26
Integer(Time.new) #=> 1049896590
Kernel#Pathname
[править]Pathname(path)
create a pathname object. This method is available since 1.8.5.
Kernel#String
[править]String(arg) => string
Converts arg to a String by calling its to_s method.
String(self) #=> "main"
String(self.class #=> "Object"
String(123456) #=> "123456"
Kernel#URI
[править]URI(uri_str)
alias for URI.parse. This method is introduced at 1.8.2.
Kernel#`
[править]`cmd` => string
Returns the standard output of running cmd in a subshell. The built-in syntax %x{...} uses this method. Sets $? to the process status.
`date` #=> "Wed Apr 9 08:56:30 CDT 2003\n"
`ls testdir`.split[1] #=> "main.rb"
`echo oops && exit 99` #=> "oops\n"
$?.exitstatus #=> 99
Kernel#abort
[править]abort Kernel::abort Process::abort
Terminate execution immediately, effectively by calling Kernel.exit(1). If msg is given, it is written to STDERR prior to terminating.
Kernel#at_exit
[править] at_exit { block } -> proc
Converts block to a Proc object (and therefore binds it at the point of call) and registers it for execution when the program exits. If multiple handlers are registered, they are executed in reverse order of registration.
def do_at_exit(str1)
at_exit { print str1 }
end
at_exit { puts "cruel world" }
do_at_exit("goodbye ")
exit
produces:
goodbye cruel world
Kernel#autoload
[править]autoload(module, filename) => nil
Registers filename to be loaded (using Kernel::require) the first time that module (which may be a String or a symbol) is accessed.
autoload(:MyModule, "/usr/local/lib/modules/my_module.rb")
Kernel#autoload?
[править]autoload(module, filename) => nil
Registers filename to be loaded (using Kernel::require) the first time that module (which may be a String or a symbol) is accessed.
autoload(:MyModule, "/usr/local/lib/modules/my_module.rb")
Kernel#binding
[править]binding -> a_binding
Returns a Binding object, describing the variable and method bindings at the point of call. This object can be used when calling eval to execute the evaluated command in this environment. Also see the description of class Binding.
def getBinding(param)
return binding
end
b = getBinding("hello")
eval("param", b) #=> "hello"
Kernel#block_given?
[править]block_given? => true or false iterator? => true or false
Returns true if yield would execute a block in the current context. The iterator? form is mildly deprecated.
def try
if block_given?
yield
else
"no block"
end
end
try #=> "no block"
try { "hello" } #=> "hello"
try do "hello" end #=> "hello"
Kernel#callcc
[править] callcc {|cont| block } => obj
Generates a Continuation object, which it passes to the associated block. Performing a cont.call will cause the callcc to return (as will falling through the end of the block). The value returned by the callcc is the value of the block, or the value passed to cont.call. See class Continuation for more details. Also see Kernel::throw for an alternative mechanism for unwinding a call stack.
Kernel#caller
[править]caller(start=1) => array
Returns the current execution stack---an array containing strings in the form ``file:line or ``file:line: in `method'. The optional start parameter determines the number of initial stack entries to omit from the result.
def a(skip)
caller(skip)
end
def b(skip)
a(skip)
end
def c(skip)
b(skip)
end
c(0) #=> ["prog:2:in `a'", "prog:5:in `b'", "prog:8:in `c'", "prog:10"]
c(1) #=> ["prog:5:in `b'", "prog:8:in `c'", "prog:11"]
c(2) #=> ["prog:8:in `c'", "prog:12"]
c(3) #=> ["prog:13"]
Kernel#catch
[править] catch(symbol) {| | block } > obj
catch executes its block. If a throw is executed, Ruby searches up its stack for a catch block with a tag corresponding to the throw's symbol. If found, that block is terminated, and catch returns the value given to throw. If throw is not called, the block terminates normally, and the value of catch is the value of the last expression evaluated. catch expressions may be nested, and the throw call need not be in lexical scope.
def routine(n)
puts n
throw :done if n <= 0
routine(n-1)
end
catch(:done) { routine(3) }
produces:
3
2
1
0
Kernel#chomp
[править]chomp => $_ chomp(string) => $_
Equivalent to $_ = $_.chomp(string). See String#chomp.
$_ = "now\n"
chomp #=> "now"
$_ #=> "now"
chomp "ow" #=> "n"
$_ #=> "n"
chomp "xxx" #=> "n"
$_ #=> "n"
Kernel#chomp!
[править]chomp! => $_ or nil chomp!(string) => $_ or nil
Equivalent to $_.chomp!(string). See String#chomp!
$_ = "now\n"
chomp! #=> "now"
$_ #=> "now"
chomp! "x" #=> nil
$_ #=> "now"
Kernel#chop
[править]chop => string
Equivalent to ($_.dup).chop!, except nil is never returned. See String#chop!.
a = "now\r\n"
$_ = a
chop #=> "now"
$_ #=> "now"
chop #=> "no"
chop #=> "n"
chop #=> ""
chop #=> ""
a #=> "now\r\n"
Kernel#chop!
[править]chop! => $_ or nil
Equivalent to $_.chop!.
a = "now\r\n"
$_ = a
chop! #=> "now"
chop! #=> "no"
chop! #=> "n"
chop! #=> ""
chop! #=> nil
$_ #=> ""
a #=> ""
Kernel#eval
[править]eval(string [, binding [, filename [,lineno]]]) => obj
Evaluates the Ruby expression(s) in string. If binding is given, the evaluation is performed in its context. The binding may be a Binding object or a Proc object. If the optional filename and lineno parameters are present, they will be used when reporting syntax errors.
def getBinding(str)
return binding
end
str = "hello"
eval "str + ' Fred'" #=> "hello Fred"
eval "str + ' Fred'", getBinding("bye") #=> "bye Fred"
Kernel#exec
[править]exec(command [, arg, ...])
Replaces the current process by running the given external command. If exec is given a single argument, that argument is taken as a line that is subject to shell expansion before being executed. If multiple arguments are given, the second and subsequent arguments are passed as parameters to command with no shell expansion. If the first argument is a two-element array, the first element is the command to be executed, and the second argument is used as the argv[0] value, which may show up in process listings. In MSDOS environments, the command is executed in a subshell; otherwise, one of the exec(2) system calls is used, so the running command may inherit some of the environment of the original program (including open file descriptors).
exec "echo *" # echoes list of files in current directory
# never get here
exec "echo", "*" # echoes an asterisk
# never get here
Kernel#exit
[править]exit(integer=0) Kernel::exit(integer=0) Process::exit(integer=0)
Initiates the termination of the Ruby script by raising the SystemExit exception. This exception may be caught. The optional parameter is used to return a status code to the invoking environment.
begin
exit
puts "never get here"
rescue SystemExit
puts "rescued a SystemExit exception"
end
puts "after begin block"
produces:
rescued a SystemExit exception
after begin block
Just prior to termination, Ruby executes any at_exit functions (see Kernel::at_exit) and runs any object finalizers (see ObjectSpace::define_finalizer).
at_exit { puts "at_exit function" }
ObjectSpace.define_finalizer("string", proc { puts "in finalizer" })
exit
produces:
at_exit function
in finalizer
Kernel#exit!
[править]Process.exit!(fixnum=-1)
Exits the process immediately. No exit handlers are run. fixnum is returned to the underlying system as the exit status.
Process.exit!(0)
Kernel#fail
[править]raise raise(string) raise(exception [, string [, array]]) fail fail(string) fail(exception [, string [, array]])
With no arguments, raises the exception in $! or raises a RuntimeError if $! is nil. With a single String argument, raises a RuntimeError with the string as a message. Otherwise, the first parameter should be the name of an Exception class (or an object that returns an Exception object when sent an exception message). The optional second parameter sets the message associated with the exception, and the third parameter is an array of callback information. Exceptions are caught by the rescue clause of begin...end blocks.
raise "Failed to create socket"
raise ArgumentError, "No parameters", caller
Более одного метода удовлетворяет вашему запросу. Вы можете уточнить ваш запрос, выбрав один из следующих методов:
Kernel#fork, Kernel#fork===Kernel#format===
format(format_string [, arguments...] ) => string sprintf(format_string [, arguments...] ) => string
Returns the string resulting from applying format_string to any additional arguments. Within the format string, any characters other than format sequences are copied to the result. A format sequence consists of a percent sign, followed by optional flags, width, and precision indicators, then terminated with a field type character. The field type controls how the corresponding sprintf argument is to be interpreted, while the flags modify that interpretation. The field type characters are listed in the table at the end of this section. The flag characters are:
Flag | Applies to | Meaning
---------+--------------+-----------------------------------------
space | bdeEfgGiouxX | Leave a space at the start of
| | positive numbers.
---------+--------------+-----------------------------------------
(digit)$ | all | Specifies the absolute argument number
| | for this field. Absolute and relative
| | argument numbers cannot be mixed in a
| | sprintf string.
---------+--------------+-----------------------------------------
# | beEfgGoxX | Use an alternative format. For the
| | conversions `o', `x', `X', and `b',
| | prefix the result with ``0, ``0x, ``0X,
| | and ``0b, respectively. For `e',
| | `E', `f', `g', and 'G', force a decimal
| | point to be added, even if no digits follow.
| | For `g' and 'G', do not remove trailing zeros.
---------+--------------+-----------------------------------------
+ | bdeEfgGiouxX | Add a leading plus sign to positive numbers.
---------+--------------+-----------------------------------------
- | all | Left-justify the result of this conversion.
---------+--------------+-----------------------------------------
0 (zero) | bdeEfgGiouxX | Pad with zeros, not spaces.
---------+--------------+-----------------------------------------
* | all | Use the next argument as the field width.
| | If negative, left-justify the result. If the
| | asterisk is followed by a number and a dollar
| | sign, use the indicated argument as the width.
The field width is an optional integer, followed optionally by a period and a precision. The width specifies the minimum number of characters that will be written to the result for this field. For numeric fields, the precision controls the number of decimal places displayed. For string fields, the precision determines the maximum number of characters to be copied from the string. (Thus, the format sequence %10.10s will always contribute exactly ten characters to the result.) The field types are:
Field | Conversion
------+--------------------------------------------------------------
b | Convert argument as a binary number.
c | Argument is the numeric code for a single character.
d | Convert argument as a decimal number.
E | Equivalent to `e', but uses an uppercase E to indicate
| the exponent.
e | Convert floating point argument into exponential notation
| with one digit before the decimal point. The precision
| determines the number of fractional digits (defaulting to six).
f | Convert floating point argument as [-]ddd.ddd,
| where the precision determines the number of digits after
| the decimal point.
G | Equivalent to `g', but use an uppercase `E' in exponent form.
g | Convert a floating point number using exponential form
| if the exponent is less than -4 or greater than or
| equal to the precision, or in d.dddd form otherwise.
i | Identical to `d'.
o | Convert argument as an octal number.
p | The valuing of argument.inspect.
s | Argument is a string to be substituted. If the format
| sequence contains a precision, at most that many characters
| will be copied.
u | Treat argument as an unsigned decimal number. Negative integers
| are displayed as a 32 bit two's complement plus one for the
| underlying architecture; that is, 2 ** 32 + n. However, since
| Ruby has no inherent limit on bits used to represent the
| integer, this value is preceded by two dots (..) in order to
| indicate a infinite number of leading sign bits.
X | Convert argument as a hexadecimal number using uppercase
| letters. Negative numbers will be displayed with two
| leading periods (representing an infinite string of
| leading 'FF's.
x | Convert argument as a hexadecimal number.
| Negative numbers will be displayed with two
| leading periods (representing an infinite string of
| leading 'ff's.
Examples:
sprintf("%d %04x", 123, 123) #=> "123 007b"
sprintf("%08b '%4s'", 123, 123) #=> "01111011 ' 123'"
sprintf("%1$*2$s %2$d %1$s", "hello", 8) #=> " hello 8 hello"
sprintf("%1$*2$s %2$d", "hello", -8) #=> "hello -8"
sprintf("%+g:% g:%-g", 1.23, 1.23, 1.23) #=> "+1.23: 1.23:1.23"
sprintf("%u", -123) #=> "..4294967173"
Kernel#gem
[править]gem(gem_name, *version_requirements)
Adds a Ruby Gem to the $LOAD_PATH. Before a Gem is loaded, its required Gems are loaded. If the version information is omitted, the highest version Gem of the supplied name is loaded. If a Gem is not found that meets the version requirement and/or a required Gem is not found, a Gem::LoadError is raised. More information on version requirements can be found in the Gem::Version documentation. The gem directive should be executed before any require statements (otherwise rubygems might select a conflicting library version). You can define the environment variable GEM_SKIP as a way to not load specified gems. you might do this to test out changes that haven't been intsalled yet. Example:
GEM_SKIP=libA:libB ruby-I../libA -I../libB ./mycode.rb
[String or Gem::Dependency] The gem name or dependency instance. [default=">= 0.0.0"] The version requirement. [Boolean] true if the Gem is loaded, otherwise false.
[Gem::LoadError] if Gem cannot be found, is listed in GEM_SKIP, or version requirement not met.Kernel#getc
[править]getc()
obsolete
Kernel#gets
[править]gets(separator=$/) => string or nil
Returns (and assigns to $_) the next line from the list of files in ARGV (or $*), or from standard input if no files are present on the command line. Returns nil at end of file. The optional argument specifies the record separator. The separator is included with the contents of each record. A separator of nil reads the entire contents, and a zero-length separator reads the input one paragraph at a time, where paragraphs are divided by two consecutive newlines. If multiple filenames are present in ARGV, +gets(nil)+ will read the contents one file at a time.
ARGV << "testfile"
print while gets
produces:
This is line one
This is line two
This is line three
And so on...
The style of programming using $_ as an implicit parameter is gradually losing favor in the Ruby community.
Kernel#global_variables
[править]global_variables => array
Returns an array of the names of global variables.
global_variables.grep /std/ #=> ["$stderr", "$stdout", "$stdin"]
Kernel#gsub
[править] gsub(pattern, replacement) => string
gsub(pattern) {|...| block } => string
Equivalent to $_.gsub..., except that $_ receives the modified result.
$_ = "quick brown fox"
gsub /[aeiou]/, '*' #=> "q**ck br*wn f*x"
$_ #=> "q**ck br*wn f*x"
Kernel#gsub!
[править] gsub!(pattern, replacement) => string or nil
gsub!(pattern) {|...| block } => string or nil
Equivalent to Kernel::gsub, except nil is returned if $_ is not modified.
$_ = "quick brown fox"
gsub! /cat/, '*' #=> nil
$_ #=> "quick brown fox"
Kernel#iterator?
[править]block_given? => true or false iterator? => true or false
Returns true if yield would execute a block in the current context. The iterator? form is mildly deprecated.
def try
if block_given?
yield
else
"no block"
end
end
try #=> "no block"
try { "hello" } #=> "hello"
try do "hello" end #=> "hello"
Kernel#lambda
[править] proc { |...| block } => a_proc
lambda { |...| block } => a_proc
Equivalent to Proc.new, except the resulting Proc objects check the number of parameters passed when called.
Kernel#load
[править]load(filename, wrap=false) => true
Loads and executes the Ruby program in the file filename. If the filename does not resolve to an absolute path, the file is searched for in the library directories listed in $:. If the optional wrap parameter is true, the loaded script will be executed under an anonymous module, protecting the calling program's global namespace. In no circumstance will any local variables in the loaded file be propagated to the loading environment.
Kernel#local_variables
[править]local_variables => array
Returns the names of the current local variables.
fred = 1
for i in 1..10
# ...
end
local_variables #=> ["fred", "i"]
Kernel#loop
[править] loop {|| block }
Repeatedly executes the block.
loop do
print "Input: "
line = gets
break if !line or line =~ /^qQ/
# ...
end
Kernel#method_missing
[править]obj.method_missing(symbol [, *args] ) => result
Invoked by Ruby when obj is sent a message it cannot handle. symbol is the symbol for the method called, and args are any arguments that were passed to it. By default, the interpreter raises an error when this method is called. However, it is possible to override the method to provide more dynamic behavior. The example below creates a class Roman, which responds to methods with names consisting of roman numerals, returning the corresponding integer values.
class Roman
def romanToInt(str)
# ...
end
def method_missing(methId)
str = methId.id2name
romanToInt(str)
end
end
r = Roman.new
r.iv #=> 4
r.xxiii #=> 23
r.mm #=> 2000
Более одного метода удовлетворяет вашему запросу. Вы можете уточнить ваш запрос, выбрав один из следующих методов:
Kernel#open, Kernel#open_uri_original_open, Kernel#open===Kernel#open_uri_original_open===
open_uri_original_open(...)
Alias for #open
Kernel#p
[править]p(obj, ...) => nil
For each object, directly writes obj.inspect followed by the current output record separator to the program's standard output.
S = Struct.new(:name, :state)
s = S['dave', 'TX']
p s
produces:
#<S name="dave", state="TX">
Kernel#pp
[править]pp(*objs)
prints arguments in pretty form. pp returns nil.
Kernel#pretty_inspect
[править]pretty_inspect()
returns a pretty printed object as a string.
Kernel#print
[править]print(obj, ...) => nil
Prints each object in turn to $stdout. If the output field separator ($,) is not nil, its contents will appear between each field. If the output record separator ($\) is not nil, it will be appended to the output. If no arguments are given, prints $_. Objects that aren't strings will be converted by calling their to_s method.
print "cat", [1,2,3], 99, "\n"
$, = ", "
$\ = "\n"
print "cat", [1,2,3], 99
produces:
cat12399
cat, 1, 2, 3, 99
Kernel#printf
[править]printf(io, string [, obj ... ] ) => nil printf(string [, obj ... ] ) => nil
Equivalent to:
io.write(sprintf(string, obj, ...)
or
$stdout.write(sprintf(string, obj, ...)
Kernel#proc
[править] proc { |...| block } => a_proc
lambda { |...| block } => a_proc
Equivalent to Proc.new, except the resulting Proc objects check the number of parameters passed when called.
Kernel#putc
[править]putc(int) => int
Equivalent to:
$stdout.putc(int)
Kernel#puts
[править]puts(obj, ..., ...) => nil
Equivalent to
$stdout.puts(obj, ...)
Kernel#raise
[править]raise raise(string) raise(exception [, string [, array]]) fail fail(string) fail(exception [, string [, array]])
With no arguments, raises the exception in $! or raises a RuntimeError if $! is nil. With a single String argument, raises a RuntimeError with the string as a message. Otherwise, the first parameter should be the name of an Exception class (or an object that returns an Exception object when sent an exception message). The optional second parameter sets the message associated with the exception, and the third parameter is an array of callback information. Exceptions are caught by the rescue clause of begin...end blocks.
raise "Failed to create socket"
raise ArgumentError, "No parameters", caller
Kernel#rake_dup
[править]rake_dup()
Duplicate an object if it can be duplicated. If it can not be cloned or duplicated, then just return the original object.
Kernel#rand
[править]rand(max=0) => number
Converts max to an integer using max1 = max.to_i.abs. If the result is zero, returns a pseudorandom floating point number greater than or equal to 0.0 and less than 1.0. Otherwise, returns a pseudorandom integer greater than or equal to zero and less than max1. Kernel::srand may be used to ensure repeatable sequences of random numbers between different runs of the program. Ruby currently uses a modified Mersenne Twister with a period of 219937-1.
srand 1234 #=> 0
[ rand, rand ] #=> [0.191519450163469, 0.49766366626136]
[ rand(10), rand(1000) ] #=> [6, 817]
srand 1234 #=> 1234
[ rand, rand ] #=> [0.191519450163469, 0.49766366626136]
Kernel#readline
[править]readline(separator=$/) => string
Equivalent to Kernel::gets, except readline raises EOFError at end of file.
Kernel#readlines
[править]readlines(separator=$/) => array
Returns an array containing the lines returned by calling Kernel.gets(separator) until the end of file.
Kernel#require
[править]require(string) => true or false
Ruby tries to load the library named string, returning true if successful. If the filename does not resolve to an absolute path, it will be searched for in the directories listed in $:. If the file has the extension ``.rb, it is loaded as a source file; if the extension is ``.so, ``.o, or ``.dll, or whatever the default shared library extension is on the current platform, Ruby loads the shared library as a Ruby extension. Otherwise, Ruby tries adding ``.rb, ``.so, and so on to the name. The name of the loaded feature is added to the array in $". A feature will not be loaded if it's name already appears in $". However, the file name is not converted to an absolute path, so that ``require 'a';require './a' will load a.rb twice.
require "my-library.rb"
require "db-driver"
Kernel#require_gem
[править]require_gem(gem_name, *version_requirements)
Same as the gem command, but will also require a file if the gem provides an auto-required file name. DEPRECATED! Use gem instead.
Kernel#scan
[править] scan(pattern) => array
scan(pattern) {|///| block } => $_
Equivalent to calling $_.scan. See String#scan.
Kernel#scanf
[править]scanf(fs,&b)
(нет описания...)
Kernel#select
[править]IO.select(read_array [, write_array [, error_array [, timeout]]] ) => array or nil
See Kernel#select.
Kernel#set_trace_func
[править]set_trace_func(proc) => proc set_trace_func(nil) => nil
Establishes proc as the handler for tracing, or disables tracing if the parameter is nil. proc takes up to six parameters: an event name, a filename, a line number, an object id, a binding, and the name of a class. proc is invoked whenever an event occurs. Events are: c-call (call a C-language routine), c-return (return from a C-language routine), call (call a Ruby method), class (start a class or module definition), end (finish a class or module definition), line (execute code on a new line), raise (raise an exception), and return (return from a Ruby method). Tracing is disabled within the context of proc.
class Test
def test
a = 1
b = 2
end
end
set_trace_func proc { |event, file, line, id, binding, classname|
printf "%8s %s:%-2d %10s %8s\n", event, file, line, id, classname
}
t = Test.new
t.test
line prog.rb:11 false
c-call prog.rb:11 new Class
c-call prog.rb:11 initialize Object
c-return prog.rb:11 initialize Object
c-return prog.rb:11 new Class
line prog.rb:12 false
call prog.rb:2 test Test
line prog.rb:3 test Test
line prog.rb:4 test Test
return prog.rb:4 test Test
Kernel#sleep
[править]sleep([duration]) => fixnum
Suspends the current thread for duration seconds (which may be any number, including a Float with fractional seconds). Returns the actual number of seconds slept (rounded), which may be less than that asked for if another thread calls Thread#run. Zero arguments causes sleep to sleep forever.
Time.new #=> Wed Apr 09 08:56:32 CDT 2003
sleep 1.2 #=> 1
Time.new #=> Wed Apr 09 08:56:33 CDT 2003
sleep 1.9 #=> 2
Time.new #=> Wed Apr 09 08:56:35 CDT 2003
Kernel#split
[править]split([pattern [, limit]]) => array
Equivalent to $_.split(pattern, limit). See String#split.
Kernel#sprintf
[править]format(format_string [, arguments...] ) => string sprintf(format_string [, arguments...] ) => string
Returns the string resulting from applying format_string to any additional arguments. Within the format string, any characters other than format sequences are copied to the result. A format sequence consists of a percent sign, followed by optional flags, width, and precision indicators, then terminated with a field type character. The field type controls how the corresponding sprintf argument is to be interpreted, while the flags modify that interpretation. The field type characters are listed in the table at the end of this section. The flag characters are:
Flag | Applies to | Meaning
---------+--------------+-----------------------------------------
space | bdeEfgGiouxX | Leave a space at the start of
| | positive numbers.
---------+--------------+-----------------------------------------
(digit)$ | all | Specifies the absolute argument number
| | for this field. Absolute and relative
| | argument numbers cannot be mixed in a
| | sprintf string.
---------+--------------+-----------------------------------------
# | beEfgGoxX | Use an alternative format. For the
| | conversions `o', `x', `X', and `b',
| | prefix the result with ``0, ``0x, ``0X,
| | and ``0b, respectively. For `e',
| | `E', `f', `g', and 'G', force a decimal
| | point to be added, even if no digits follow.
| | For `g' and 'G', do not remove trailing zeros.
---------+--------------+-----------------------------------------
+ | bdeEfgGiouxX | Add a leading plus sign to positive numbers.
---------+--------------+-----------------------------------------
- | all | Left-justify the result of this conversion.
---------+--------------+-----------------------------------------
0 (zero) | bdeEfgGiouxX | Pad with zeros, not spaces.
---------+--------------+-----------------------------------------
* | all | Use the next argument as the field width.
| | If negative, left-justify the result. If the
| | asterisk is followed by a number and a dollar
| | sign, use the indicated argument as the width.
The field width is an optional integer, followed optionally by a period and a precision. The width specifies the minimum number of characters that will be written to the result for this field. For numeric fields, the precision controls the number of decimal places displayed. For string fields, the precision determines the maximum number of characters to be copied from the string. (Thus, the format sequence %10.10s will always contribute exactly ten characters to the result.) The field types are:
Field | Conversion
------+--------------------------------------------------------------
b | Convert argument as a binary number.
c | Argument is the numeric code for a single character.
d | Convert argument as a decimal number.
E | Equivalent to `e', but uses an uppercase E to indicate
| the exponent.
e | Convert floating point argument into exponential notation
| with one digit before the decimal point. The precision
| determines the number of fractional digits (defaulting to six).
f | Convert floating point argument as [-]ddd.ddd,
| where the precision determines the number of digits after
| the decimal point.
G | Equivalent to `g', but use an uppercase `E' in exponent form.
g | Convert a floating point number using exponential form
| if the exponent is less than -4 or greater than or
| equal to the precision, or in d.dddd form otherwise.
i | Identical to `d'.
o | Convert argument as an octal number.
p | The valuing of argument.inspect.
s | Argument is a string to be substituted. If the format
| sequence contains a precision, at most that many characters
| will be copied.
u | Treat argument as an unsigned decimal number. Negative integers
| are displayed as a 32 bit two's complement plus one for the
| underlying architecture; that is, 2 ** 32 + n. However, since
| Ruby has no inherent limit on bits used to represent the
| integer, this value is preceded by two dots (..) in order to
| indicate a infinite number of leading sign bits.
X | Convert argument as a hexadecimal number using uppercase
| letters. Negative numbers will be displayed with two
| leading periods (representing an infinite string of
| leading 'FF's.
x | Convert argument as a hexadecimal number.
| Negative numbers will be displayed with two
| leading periods (representing an infinite string of
| leading 'ff's.
Examples:
sprintf("%d %04x", 123, 123) #=> "123 007b"
sprintf("%08b '%4s'", 123, 123) #=> "01111011 ' 123'"
sprintf("%1$*2$s %2$d %1$s", "hello", 8) #=> " hello 8 hello"
sprintf("%1$*2$s %2$d", "hello", -8) #=> "hello -8"
sprintf("%+g:% g:%-g", 1.23, 1.23, 1.23) #=> "+1.23: 1.23:1.23"
sprintf("%u", -123) #=> "..4294967173"
Kernel#srand
[править]srand(number=0) => old_seed
Seeds the pseudorandom number generator to the value of number.to_i.abs. If number is omitted or zero, seeds the generator using a combination of the time, the process id, and a sequence number. (This is also the behavior if Kernel::rand is called without previously calling srand, but without the sequence.) By setting the seed to a known value, scripts can be made deterministic during testing. The previous seed value is returned. Also see Kernel::rand.
Kernel#sub
[править] sub(pattern, replacement) => $_
sub(pattern) { block } => $_
Equivalent to $_.sub(args), except that $_ will be updated if substitution occurs.
Kernel#sub!
[править] sub!(pattern, replacement) => $_ or nil
sub!(pattern) {|...| block } => $_ or nil
Equivalent to $_.sub!(args).
Kernel#syscall
[править]syscall(fixnum [, args...]) => integer
Calls the operating system function identified by fixnum, passing in the arguments, which must be either String objects, or Integer objects that ultimately fit within a native long. Up to nine parameters may be passed (14 on the Atari-ST). The function identified by fixnum is system dependent. On some Unix systems, the numbers may be obtained from a header file called syscall.h.
syscall 4, 1, "hello\n", 6 # '4' is write(2) on our box
produces:
hello
Kernel#system
[править]system(cmd [, arg, ...]) => true or false
Executes cmd in a subshell, returning true if the command was found and ran successfully, false otherwise. An error status is available in $?. The arguments are processed in the same way as for Kernel::exec.
system("echo *")
system("echo", "*")
produces:
config.h main.rb
*
Kernel#test
[править]test(int_cmd, file1 [, file2] ) => obj
Uses the integer aCmd to perform various tests on
file1 (first table below) or on file1 and
file2 (second table).
File tests on a single file:
Test Returns Meaning
?A | Time | Last access time for file1
?b | boolean | True if file1 is a block device
?c | boolean | True if file1 is a character device
?C | Time | Last change time for file1
?d | boolean | True if file1 exists and is a directory
?e | boolean | True if file1 exists
?f | boolean | True if file1 exists and is a regular file
?g | boolean | True if file1 has the \CF{setgid} bit
| | set (false under NT)
?G | boolean | True if file1 exists and has a group
| | ownership equal to the caller's group
?k | boolean | True if file1 exists and has the sticky bit set
?l | boolean | True if file1 exists and is a symbolic link
?M | Time | Last modification time for file1
?o | boolean | True if file1 exists and is owned by
| | the caller's effective uid
?O | boolean | True if file1 exists and is owned by
| | the caller's real uid
?p | boolean | True if file1 exists and is a fifo
?r | boolean | True if file1 is readable by the effective
| | uid/gid of the caller
?R | boolean | True if file is readable by the real
| | uid/gid of the caller
?s | int/nil | If file1 has nonzero size, return the size,
| | otherwise return nil
?S | boolean | True if file1 exists and is a socket
?u | boolean | True if file1 has the setuid bit set
?w | boolean | True if file1 exists and is writable by
| | the effective uid/gid
?W | boolean | True if file1 exists and is writable by
| | the real uid/gid
?x | boolean | True if file1 exists and is executable by
| | the effective uid/gid
?X | boolean | True if file1 exists and is executable by
| | the real uid/gid
?z | boolean | True if file1 exists and has a zero length
Tests that take two files:
?- | boolean | True if file1 and file2 are identical
?= | boolean | True if the modification times of file1
| | and file2 are equal
?< | boolean | True if the modification time of file1
| | is prior to that of file2
?> | boolean | True if the modification time of file1
| | is after that of file2
Kernel#throw
[править]throw(symbol [, obj])
Transfers control to the end of the active catch block waiting for symbol. Raises NameError if there is no catch block for the symbol. The optional second parameter supplies a return value for the catch block, which otherwise defaults to nil. For examples, see Kernel::catch.
Kernel#to_ptr
[править]to_ptr()
Allows arbitrary objects to be passed as a pointer to functions. (Probably not very GC safe, but by encapsulating it like this we can change the implementation later.)
Kernel#trace_var
[править] trace_var(symbol, cmd ) => nil
trace_var(symbol) {|val| block } => nil
Controls tracing of assignments to global variables. The parameter +symbol_ identifies the variable (as either a string name or a symbol identifier). cmd (which may be a string or a Proc object) or block is executed whenever the variable is assigned. The block or Proc object receives the variable's new value as a parameter. Also see Kernel::untrace_var.
trace_var :$_, proc {|v| puts "$_ is now '#{v}'" }
$_ = "hello"
$_ = ' there'
produces:
$_ is now 'hello'
$_ is now ' there'
Kernel#trap
[править] Signal.trap( signal, proc ) => obj
Signal.trap( signal ) {| | block } => obj
Specifies the handling of signals. The first parameter is a signal name (a string such as ``SIGALRM, ``SIGUSR1, and so on) or a signal number. The characters ``SIG may be omitted from the signal name. The command or block specifies code to be run when the signal is raised. If the command is the string ``IGNORE or ``SIG_IGN, the signal will be ignored. If the command is ``DEFAULT or ``SIG_DFL, the operating system's default handler will be invoked. If the command is ``EXIT, the script will be terminated by the signal. Otherwise, the given command or block will be run. The special signal name ``EXIT or signal number zero will be invoked just prior to program termination. trap returns the previous handler for the given signal.
Signal.trap(0, proc { puts "Terminating: #{$$}" })
Signal.trap("CLD") { puts "Child died" }
fork && Process.wait
produces:
Terminating: 27461
Child died
Terminating: 27460
Kernel#untrace_var
[править]untrace_var(symbol [, cmd] ) => array or nil
Removes tracing for the specified command on the given global variable and returns nil. If no command is specified, removes all tracing for that variable and returns an array containing the commands actually removed.
Kernel#warn
[править]warn(msg)
(нет описания...)
Kernel#y
[править]y( object, *objects )
Prints any supplied objects out in YAML. Intended as a variation on +Kernel::p+.
S = Struct.new(:name, :state)
s = S['dave', 'TX']
y s
_produces:_
--- !ruby/struct:S
name: dave
state: TX