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irb(1) [osx man page]

IRB(1)							 Ruby Programmers Reference Guide						    IRB(1)

irb -- Interactive Ruby Shell SYNOPSIS
irb [--version] [-dfm] [-I directory] [-r library] [--[no]inspect] [--[no]readline] [--prompt mode] [--prompt-mode mode] [--inf-ruby-mode] [--simple-prompt] [--noprompt] [--tracer] [--back-trace-limit n] [--irb_debug n] [--] [program_file] [argument ...] DESCRIPTION
irb is the REPL(read-eval-print loop) environment for Ruby programs. OPTIONS
--version Prints the version of irb. -E external[:internal] --encoding external[:internal] Same as `ruby -E' . Specifies the default value(s) for external encodings and internal encoding. Values should be separated with colon (:). You can omit the one for internal encodings, then the value (Encoding.default_internal) will be nil. -I path Same as `ruby -I' . Specifies $LOAD_PATH directory -U Same as `ruby -U' . Sets the default value for internal encodings (Encoding.default_internal) to UTF-8. -d Same as `ruby -d' . Sets $DEBUG to true. -f Suppresses read of ~/.irbrc. -h --help Prints a summary of the options. -m Bc mode (load mathn, fraction or matrix are available) -r library Same as `ruby -r'. Causes irb to load the library using require. --inspect Uses `inspect' for output (default except for bc mode) --noinspect Doesn't use inspect for output --readline Uses Readline extension module. --noreadline Doesn't use Readline extension module. --prompt mode --prompt-mode mode Switch prompt mode. Pre-defined prompt modes are `default', `simple', `xmp' and `inf-ruby'. --inf-ruby-mode Uses prompt appropriate for inf-ruby-mode on emacs. Suppresses --readline. --simple-prompt Makes prompts simple. --noprompt No prompt mode. --tracer Displays trace for each execution of commands. --back-trace-limit n Displays backtrace top n and tail n. The default value is 16. --irb_debug n Sets internal debug level to n (not for popular use) ENVIRONMENT
IRBRC Also irb depends on same variables as ruby(1). FILES
~/.irbrc Personal irb initialization. EXAMPLES
% irb irb(main):001:0> 1 + 1 2 irb(main):002:0> def t(x) irb(main):003:1> x+1 irb(main):004:1> end => nil irb(main):005:0> t(3) => 4 irb(main):006:0> if t(3) == 4 irb(main):007:1> p :ok irb(main):008:1> end :ok => :ok irb(main):009:0> quit % SEE ALSO
Security vulnerabilities should be reported via an email to <>. Reported problems will be published after being fixed. And you can report other bugs and feature requests via the Ruby Issue Tracking System ( Do not report security vulnerabilities via the system because it publishes the vulnerabilities immediately. AUTHORS
Written by Keiju ISHITSUKA. UNIX
November 7, 2012 UNIX

Check Out this Related Man Page

irb-beta(1)						      General Commands Manual						       irb-beta(1)

What is irb?
       irb stands for `interactive ruby'. irb is a tool to execute interactively ruby expressions read from stdin.

	   % ruby -r irb -e0
	   % irb
       Either of the aboves. In the former style, options can be specified as follows:
	   % ruby -r irb -e0 -- -v

       Use  of irb is easy if you know ruby.  Executing irb, prompts are displayed as follows. Then, enter expression of ruby. A input is executed
       when it is syntacticaly completed.
	   dim% irb
	   irb(main):001:0> 1+2
	   irb(main):002:0> class Foo
	   irb(main):003:1>  def foo
	   irb(main):004:2>    print 1
	   irb(main):005:2>  end
	   irb(main):006:1> end
       And, Readline extesion module can be used with irb. Using Readline is the standard default action if Readline is installed.

Command line option
	   irb.rb [options] file_name opts
	   -f		  suppress read ~/.irbrc
	   -m		  bc mode (fraction or matrix are available)
	   -d		     set $DEBUG  to true (same as `ruby -d')
	   -r load-module    same as `ruby -r'
	   --inspect	  uses `inspect' for output (the default except bc mode)
	   --noinspect	       doesn't uses inspect for output
	   --readline	  uses Readline extension module
	   --noreadline        doesn't use Readline extension module
	   --prompt prompt-mode
	   --prompt-mode prompt-mode
	   switches prompt mode. Pre-defined prompt modes are
	   `defalut', `simple', `xmp' and `inf-ruby'
	   --inf-ruby-mode   uses prompt appreciate for inf-ruby-mode on emacs.
	   Suppresses --readline.
	   --simple-prompt   simple prompt mode
	   --noprompt	  no prompt
	   --tracer	  display trace for each execution of commands.
	   --back-trace-limit n
	   displayes backtrace top n and tail n. The default
	   value is 16.
	   --irb_debug n       sets internal debug level to n (It shouldn't be used)
	   -v, --version       prints the version of irb

       irb reads `~/.irbrc' when it is invoked. If `~/.irbrb' doesn't exist irb try to	read  in  the  order  `.irbrc',  `irb.rc',  `_irbrc'  then
       `$irbrc'.  The following is altanative to the command line option. To use them type as follows in an irb session.
	   IRB.conf[:IRB_RC] = nil
	   IRB.conf[:USE_LOADER] = false
	   IRB.conf[:USE_READLINE] = nil
	   IRB.conf[:USE_TRACER] = false
	   IRB.conf[:IGNORE_SIGINT] = true
	   IRB.conf[:IGNORE_EOF] = false
	   IRB.conf[:PROMPT] = {...}

Customizing prompt
       To costomize the prompt you set a variable
       For example, describe as follows in `.irbrc'.
	   IRB.conf[:PROMPT][:MY_PROMPT] = { # name of prompt mode
	     :PROMPT_I => nil,	       # normal prompt
	     :PROMPT_S => nil,	       # prompt for continuated strings
	     :PROMPT_C => nil,	       # prompt for continuated statement
	     :RETURN => "    ==>%s
"	    # format to return value
       Then, invoke irb with the above prompt mode by
	   % irb --prompt my-prompt
       Or add the following in `.irbrc'.
       Constants PROMPT_I, PROMPT_S and PROMPT_C specifies the format.	In the prompt specification, some special strings are available.
	   %N	 command name which is running
	   %m	 to_s of main object (self)
	   %M	 inspect of main object (self)
	   %l	 type of string(", ', /, ]), `]' is inner %w[...]
	   %NNi  indent level. NN is degits and means as same as printf("%NNd").
		 It can be ommited
	   %NNn  line number.
	   %%	 %
       For instance, the default prompt mode is defined as follows: IRB.conf[:PROMPT_MODE][:DEFAULT] = {

       PROMPT_I => "%N(%m):%03n:%i> ",

       PROMPT_S => "%N(%m):%03n:%i%l ",

       PROMPT_C => "%N(%m):%03n:%i* ",

       RETURN => "%s
	      } RETURN is used to printf.

Configurating subirb
       The  command  line option or IRB.conf specify the default behavior of (sub)irb. On the other hand, each conf of in the next sction `6. Com-
       mand' is used to individually configurate (sub)irb.  If proc is set to IRB.conf[:IRB_RC], its subirb will be  invoked  after  execution	of
       that proc under giving the context of irb as its aregument. By this mechanism each subirb can be configurated.

       For irb commands, both simple name and `irb_'-prefixed name are prepared.

       exit, quit, irb_exit
	      Quits (sub)irb.  if you've done cb (see below), exit from the binding mode.

       conf, irb_context
	      Displays current configuration. Modifing the configuration is achieved by sending message to `conf'.

	      Sets display lines of backtrace as top n and tail n.  The default value is 16.

       conf.debug_level = N
	      Sets debug level of irb.

       conf.ignore_eof = true/false
	      Whether ^D (control-d) will be ignored or not.  If false is set, ^D means quit.

       conf.ignore_sigint= true/false
	      Whether ^C (control-c) will be ignored or not.  If false is set, ^D means quit.  If true,

		  during input:   cancel inputing then return to top level.
		  during execute: abondon current execution.

       conf.inf_ruby_mode = true/false
	      Whether inf-ruby-mode or not. The default value is false.

       conf.inspect_mode = true/false/nil
	      Specifies inspect mode.  true:  display inspect false: display to_s nil:	 inspect mode in non math mode,

		  non inspect mode in math mode.

	      The level of cb.

	      Whether bc mode or not.

       conf.use_loader = true/false
	      Whether irb's own file reader method is used when load/require or not.  This mode is globaly affected (irb wide).

	      prompt for a continuating statement (e.g, immediately after of `if')

	      standard prompt

	      prompt for a continuating string

	      Whether ~/.irbrc is read or not.

       conf.use_prompt = true/false
	      Prompting or not.

       conf.use_readline = true/false/nil
	      Whether readline is used or not.	true: uses false: doen't use nil: intends to use readline except for inf-reuby-mode (default)

	      Whether verbose messages are display or not.

       cb, irb_change_binding [obj]
	      Enter new binding which has a distinct scope of local variables.	If obj is given, obj will be self.

       irb [obj]
	      Invoke subirb. If obj is given, obj will be self.

       jobs, irb_jobs
	      List of subirb

       fg n, irb_fg n
	      Switch into specified subirb. The following is candidates of n:

		  irb number
		  irb object
		  self(obj which is specified of irb obj)

       kill n, irb_kill n
	      Kill subirb. The means of n is as same as the case of irb_fg.

System variable
	   _  The latest value of evaluation (it is local)

Session Example
	   dim% ruby irb.rb
	   irb(main):001:0> irb 		       # invoke subirb
	   irb#1(main):001:0> jobs		       # list of subirbs
	   #0->irb on main (#<Thread:0x400fb7e4> : stop)
	   #1->irb#1 on main (#<Thread:0x40125d64> : running)
	   irb#1(main):002:0> fg 0		       # switch job
	   irb(main):002:0> class Foo;end
	   irb(main):003:0> irb Foo		       # invoke subirb which has the
	   #		  context of Foo
	   irb#2(Foo):001:0> def foo		       # define Foo#foo
	   irb#2(Foo):002:1>   print 1
	   irb#2(Foo):003:1> end
	   irb#2(Foo):004:0> fg 0		       # switch job
	   irb(main):004:0> jobs		       # list of job
	   #0->irb on main (#<Thread:0x400fb7e4> : running)
	   #1->irb#1 on main (#<Thread:0x40125d64> : stop)
	   #2->irb#2 on Foo (#<Thread:0x4011d54c> : stop)
	   irb(main):005:0> Foo.instance_methods       # Foo#foo is defined asurely
	   irb(main):006:0> fg 2		       # switch job
	   irb#2(Foo):005:0> def bar		       # define Foo#bar
	   irb#2(Foo):006:1>  print "bar"
	   irb#2(Foo):007:1> end
	   irb#2(Foo):010:0>  Foo.instance_methods
	   ["bar", "foo"]
	   irb#2(Foo):011:0> fg 0
	   irb(main):007:0> f =
	   irb(main):008:0> irb f		       # invoke subirb which has the
	   #  context of f (instance of Foo)
	   irb#3(#<Foo:0x4010af3c>):001:0> jobs
	   #0->irb on main (#<Thread:0x400fb7e4> : stop)
	   #1->irb#1 on main (#<Thread:0x40125d64> : stop)
	   #2->irb#2 on Foo (#<Thread:0x4011d54c> : stop)
	   #3->irb#3 on #<Foo:0x4010af3c> (#<Thread:0x4010a1e0> : running)
	   irb#3(#<Foo:0x4010af3c>):002:0> foo	       # evaluate
	   irb#3(#<Foo:0x4010af3c>):003:0> bar	       # evaluate
	   irb#3(#<Foo:0x4010af3c>):004:0> kill 1, 2, 3# kill job
	   irb(main):009:0> jobs
	   #0->irb on main (#<Thread:0x400fb7e4> : running)
	   irb(main):010:0> exit		       # exit

       Because	irb  evaluates	the inputs immediately after the imput is syntactically completed, irb gives slight different result than directly
       use ruby. Known difference is pointed out here.

Declaration of the local variable
       The following causes an error in ruby:
	   eval "foo = 0"
	   -:2: undefined local variable or method `foo' for #<Object:0x40283118> (NameError)
       Though, the above will successfully done by irb.
	   >> eval "foo = 0"
	   => 0
	   >> foo
	   => 0
       Ruby evaluates a code after reading entire of code and determination of the scope of local variables. On the other  hand,  irb  do  immedi-
       ately. More precisely, irb evaluate at first
	   evel "foo = 0"
       then  foo  is defined on this timing. It is because of this incompatibility.  If you'd like to detect those differences, begin...end can be
	   >> begin
	   ?>	eval "foo = 0"
	   >>	foo
	   >> end
	   NameError: undefined local variable or method `foo' for #<Object:0x4013d0f0>
	   (irb_local_binding):1:in `eval'

       Implementation of Here-document is incomplete.

       Irb can not always recognize a symbol as to be Symbol. Concretely, an expression have completed, however  Irb  regard  it  as  continuation

								     May 2001							       irb-beta(1)
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