Provided by: ruby1.8_1.8.7.352-2ubuntu1_amd64 bug

NAME

       irb1.8 - interactive ruby

SYNOPSIS

       irb [options]

DESCRIPTION

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

           $ irb1.8
           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.

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 `default', `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

           $ irb1.8 --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

           $ irb1.8
           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

Restrictions

       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"
           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 differences, 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.

                                          December 2002                                 IRB1.8(1)