irb.1

.TH IRB1.8 "1" "December 2002"
.SH NAME
irb1.8 \- interactive ruby
.SH SYNOPSIS
.B irb
[\fIoptions\fR]
.SH DESCRIPTION
.PP
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. 

.nf
\&    $ 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> 
.fi

And, Readline extesion module can be used with irb. Using Readline
is the standard default action if Readline is installed. 
.SH OPTIONS

.PP

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

.PP
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. 

.nf
\&    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
.fi
.SH Customizing prompt

.PP
To costomize the prompt you set a variable

.nf
\&    IRB.conf[:PROMPT]
.fi

For example, describe as follows in `.irbrc'. 

.nf
\&    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
\&    }
.fi

Then, invoke irb with the above prompt mode by

.nf
\&    $ irb1.8 \-\-prompt my\-prompt
.fi

Or add the following in `.irbrc'. 

.nf
\&    IRB.conf[:PROMPT_MODE] = :MY_PROMPT
.fi

Constants PROMPT_I, PROMPT_S and PROMPT_C specifies the format. 
In the prompt specification, some special strings are available. 

.nf
\&    %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. 
\&    %%    %
.fi
For instance, the default prompt mode is defined as follows:
IRB.conf[:PROMPT_MODE][:DEFAULT] = {
.TP
.fi
.B
PROMPT_I => "%N(%m):%03n:%i> ",
.TP
.fi
.B
PROMPT_S => "%N(%m):%03n:%i%l ",
.TP
.fi
.B
PROMPT_C => "%N(%m):%03n:%i* ",
.TP
.fi
.B
RETURN => "%s\\n"} 
RETURN is used to printf. 
.SH Configurating subirb

.PP
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. 
.SH Command

.PP
For irb commands, both simple name and `irb_'\-prefixed name are prepared. 
.TP
.fi
.B
exit, quit, irb_exit
Quits (sub)irb. 
if you've done cb (see below), exit from the binding mode.

.TP
.fi
.B
conf, irb_context
Displays current configuration. Modifing the configuration is
achieved by sending message to `conf'. 
.TP
.fi
.B
conf.back_trace_limit
Sets display lines of backtrace as top n and tail n. 
The default value is 16.
.TP
.fi
.B
conf.debug_level = N
Sets debug level of irb. 
.TP
.fi
.B
conf.ignore_eof = true/false
Whether ^D (control\-d) will be ignored or not. 
If false is set, ^D means quit. 
.TP
.fi
.B
conf.ignore_sigint= true/false
Whether ^C (control\-c) will be ignored or not. 
If false is set, ^D means quit.  If true, 
.nf
\&    during input:   cancel inputing then return to top level. 
\&    during execute: abondon current execution. 
.fi
.TP
.fi
.B
conf.inf_ruby_mode = true/false
Whether inf\-ruby\-mode or not. The default value is false.
.TP
.fi
.B
conf.inspect_mode = true/false/nil
Specifies inspect mode. 
true:  display inspect
false: display to_s
nil:   inspect mode in non math mode, 
.nf
\&    non inspect mode in math mode. 
.fi
.TP
.fi
.B
conf.irb_level
The level of cb. 
.TP
.fi
.B
conf.math_mode
Whether bc mode or not. 
.TP
.fi
.B
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). 
.TP
.fi
.B
conf.prompt_c
prompt for a continuating statement (e.g, immediately after of `if')
.TP
.fi
.B
conf.prompt_i
standard prompt
.TP
.fi
.B
conf.prompt_s
prompt for a continuating string
.TP
.fi
.B
conf.rc
Whether ~/.irbrc is read or not. 
.TP
.fi
.B
conf.use_prompt = true/false
Prompting or not. 
.TP
.fi
.B
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)
.TP
.fi
.B
conf.verbose=T/F
Whether verbose messages are display or not. 
.TP
.fi
.B
cb, irb_change_binding [obj]
Enter new binding which has a distinct scope of local variables. 
If obj is given, obj will be self. 
.TP
.fi
.B
irb [obj]
Invoke subirb. If obj is given, obj will be self. 
.TP
.fi
.B
jobs, irb_jobs
List of subirb
.TP
.fi
.B
fg n, irb_fg n
Switch into specified subirb. The following is candidates of n:
.nf
\&    irb number
\&    thhread
\&    irb object
\&    self(obj which is specified of irb obj)
.fi
.TP
.fi
.B
kill n, irb_kill n
Kill subirb. The means of n is as same as the case of irb_fg. 
.SH System variable

.PP

.TP
.fi
.B
_
The latest value of evaluation (it is local)
.SH Session Example

.PP
.nf
\&    $ 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 
.fi
.nf
\&    #              context of Foo
.fi
.nf
\&    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
.fi
.nf
\&    #  context of f (instance of Foo)
.fi
.nf
\&    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
.fi
.SH Restrictions

.PP
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. 
.SH Declaration of the local variable

.PP
The following causes an error in ruby:

.nf
\&    eval "foo = 0"
\&    foo
\&    \-\-
\&    \-:2: undefined local variable or method `foo' for #<Object:0x40283118> (NameError)
\&    \-\-\-
\&    NameError
.fi

Though, the above will successfully done by irb. 

.nf
\&    >> eval "foo = 0"
.fi
.nf
\&    => 0
\&    >> foo
\&    => 0
.fi

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

.nf
\&    evel "foo = 0" 
.fi

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:

.nf
\&    >> begin
\&    ?>   eval "foo = 0"
\&    >>   foo
\&    >> end
\&    NameError: undefined local variable or method `foo' for #<Object:0x4013d0f0>
\&    (irb):3
\&    (irb_local_binding):1:in `eval'
.fi
.SH Here\-document

.PP
Implementation of Here\-document is incomplete. 
.SH Symbol

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