--- name: "irb1.9" section: "1" platform: "linux" package: "irb1.9" version: "1.9.0.2-9lenny1" release: "Debian 5.0 (Lenny)" platforms: ["linux"] url: "https://new.carta.tech/irb1.9" --- # irb1.9(1) interactive ruby ## NAME irb1.9 - 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 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 --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 irb(main):001:0> irb # invoke subirb irb#1(main):001:0> jobs # list of subirbs #0->irb on main (# : stop) #1->irb#1 on main (# : 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 (# : running) #1->irb#1 on main (# : stop) #2->irb#2 on Foo (# : 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 # irb(main):008:0> irb f # invoke subirb which has the ``` ``` # context of f (instance of Foo) ``` ``` irb#3(#):001:0> jobs #0->irb on main (# : stop) #1->irb#1 on main (# : stop) #2->irb#2 on Foo (# : stop) #3->irb#3 on # (# : running) nil irb#3(#):002:0> foo # evaluate f.foo 1nil irb#3(#):003:0> bar # evaluate f.bar barnil irb#3(#):004:0> kill 1, 2, 3# kill job nil irb(main):009:0> jobs #0->irb on main (# : 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 # (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 # (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.