irb stands for `interactive ruby'. irb is a tool to execute interactively ruby expressions read from stdin.
% irb
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.
irb.rb [options] file_name opts options: -f suppress read ~/.irbrc -m bc mode (fraction or matrix are available) -d set $DEBUG to true (same as `ruby -d') -Kc same as `ruby -Kc' -r load-module same as `ruby -r' --verbose command input is echoed(default) --noverbose command input isn't echoed --echo commands are echoed immediately before execution(default) --noecho commands aren't echoed immediately before execution --inspect uses `inspect' for output (the default except bc mode) --noinspect doesn't uses inspect for output --readline uses Readline extension module --noreadline doesn't use Readline extension module --prompt prompt-mode --prompt-mode prompt-mode
switches prompt mode. Pre-defined prompt modes are `default', `simple', `xmp' and `inf-ruby'
--inf-ruby-mode uses prompt appreciate for inf-ruby-mode on emacs.
Suppresses --readline.
--simple-prompt simple prompt mode --noprompt no prompt --tracer display trace for each execution of commands. --back-trace-limit n
displayes backtrace top n and tail n. The default value is 16.
--irb_debug n sets internal debug level to n (It shouldn't be used) -v, --version prints the version of irb
irb reads `~/.irbrc' when it is invoked. If `~/.irbrb' doesn't exist irb try to read in the order `.irbrc', `irb.rc', `_irbrc' then `$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
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] = {
}
RETURN is used to printf.
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.
For irb commands, both simple name and `irb_'-prefixed name are prepared.
exit, quit, irb_exitQuits (sub)irb.
conf, irb_contextDisplays current configuration. Modifing the configuration is achieved by sending message to `conf'.
conf.eval_history = NSets execution result history. N is a integer or nil. If N > 0, the number of historys is N. If N == 0, the number of historys is unlimited. If N is nill, execution result history isn't used(default).
conf.back_trace_limitSets display lines of backtrace as top n and tail n. The default value is 16.
conf.debug_level = NSets debug level of irb.
conf.ignore_eof = true/falseWhether ^D (control-d) will be ignored or not. If false is set, ^D means quit.
conf.ignore_sigint= true/falseWhether ^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/falseWhether inf-ruby-mode or not. The default value is false.
conf.inspect_mode = true/false/nilSpecifies inspect mode. true: display inspect false: display to_s nil: inspect mode in non math mode,
non inspect mode in math mode.
conf.math_modeWhether bc mode or not.
conf.use_loader = true/falseWhether irb's own file reader method is used when load/require or not. This mode is globaly affected (irb wide).
conf.prompt_cprompt for a continuating statement (e.g, immediately after of `if')
conf.prompt_istandard prompt
conf.prompt_sprompt for a continuating string
conf.rcWhether ~/.irbrc is read or not.
conf.use_prompt = true/falsePrompting or not.
conf.use_readline = true/false/nilWhether readline is used or not. true: uses false: doen't use nil: intends to use readline except for inf-reuby-mode (default)
cws, chws, irb_change_workspace [obj]obj will be self. If obj is omitted, self will be home-object, or the main object of first started irb.
pushws, irb_pushws, irb_push_workspace [obj]same as UNIX-shell command pushd.
popws, irb_popws, irb_pop_workspacesame as UNIX-shell command popd
irb [obj]Invoke subirb. If obj is given, obj will be self.
jobs, irb_jobsList of subirb
fg n, irb_fg nSwitch 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 nKill subirb. The means of n is as same as the case of irb_fg.
souce, irb_source pathThis is a like UNIX-shell command source. evaluate script in path on current context.
irb_load path, previrb-version of Ruby's load.
_ The latest value of evaluation (it is local)
__ The history of evaluation values.__[line_no] return an evaluation value of line number<line_no>. If line_no is a negative, return value before -<line_no> from latest value.
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%
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.
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'
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 line.