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RedHat 9 (Linux i386) - man page for irb (redhat section 1)

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.

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

Usage
       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
	   3
	   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
	   nil
	   irb(main):007:0>
       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
	   options:
	   -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

Configurations
       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_NAME]="irb"
	   IRB.conf[:MATH_MODE]=false
	   IRB.conf[:USE_TRACER]=false
	   IRB.conf[:USE_LOADER]=false
	   IRB.conf[:IGNORE_SIGINT]=true
	   IRB.conf[:IGNORE_EOF]=false
	   IRB.conf[:INSPECT_MODE]=nil
	   IRB.conf[:IRB_RC] = nil
	   IRB.conf[:BACK_TRACE_LIMIT]=16
	   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_MODE] = :DEFALUT
	   IRB.conf[:PROMPT] = {...}
	   IRB.conf[:DEBUG_LEVEL]=0
	   IRB.conf[:VERBOSE]=true

Customizing prompt
       To costomize the prompt you set a variable
	   IRB.conf[:PROMPT]
       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\n"	    # format to return value
	   }
       Then, invoke irb with the above prompt mode by
	   % irb --prompt my-prompt
       Or add the following in `.irbrc'.
	   IRB.conf[:PROMPT_MODE] = :MY_PROMPT
       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\n"
	      } 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.  Command'  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.

Command
       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'.

       conf.back_trace_limit
	      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.

       conf.irb_level
	      The level of cb.

       conf.math_mode
	      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).

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

       conf.prompt_i
	      standard prompt

       conf.prompt_s
	      prompt for a continuating string

       conf.rc
	      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)

       conf.verbose=T/F
	      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
		  thhread
		  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)
	   nil
	   irb#1(main):002:0> fg 0		       # switch job
	   nil
	   irb(main):002:0> class Foo;end
	   nil
	   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
	   nil
	   irb#2(Foo):004:0> fg 0		       # switch job
	   nil
	   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)
	   nil
	   irb(main):005:0> Foo.instance_methods       # Foo#foo is defined asurely
	   ["foo"]
	   irb(main):006:0> fg 2		       # switch job
	   nil
	   irb#2(Foo):005:0> def bar		       # define Foo#bar
	   irb#2(Foo):006:1>  print "bar"
	   irb#2(Foo):007:1> end
	   nil
	   irb#2(Foo):010:0>  Foo.instance_methods
	   ["bar", "foo"]
	   irb#2(Foo):011:0> fg 0
	   nil
	   irb(main):007:0> f = Foo.new
	   #<Foo:0x4010af3c>
	   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)
	   nil
	   irb#3(#<Foo:0x4010af3c>):002:0> foo	       # evaluate f.foo
	   1nil
	   irb#3(#<Foo:0x4010af3c>):003:0> bar	       # evaluate f.bar
	   barnil
	   irb#3(#<Foo:0x4010af3c>):004:0> kill 1, 2, 3# kill job
	   nil
	   irb(main):009:0> jobs
	   #0->irb on main (#<Thread:0x400fb7e4> : running)
	   nil
	   irb(main):010:0> exit		       # exit
	   dim%

Restrictions
       Because irb evaluates the inputs immediately after the imput is syntactically completed, irb gives slight dif-
       ferent 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"
	   foo
	   --
	   -:2: undefined local variable or method `foo' for #<Object:0x40283118> (NameError)
	   ---
	   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 immediately. 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 dif-
       ferences, begin...end can be used:
	   >> begin
	   ?>	eval "foo = 0"
	   >>	foo
	   >> end
	   NameError: undefined local variable or method `foo' for #<Object:0x4013d0f0>
	   (irb):3
	   (irb_local_binding):1:in `eval'

Here-document
       Implementation of Here-document is incomplete.

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

						       May 2001 					  irb-beta(1)


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