NAME¶
irb1.9.1 - 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.
$ irb1.9.1
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
$ irb1.9.1 --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¶
$ irb1.9.1
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.