IRb: how to start an interactive ruby session with pre-loaded classes

Question

As I am going through my journey by adopting the Ruby language, I spend a lot of time inside IRb. It's just fantastic! But, as I am not very aware of it's capabilities, and still a “nubby” with Ruby, I would like to know the following:

• How can I “flush” the session, without restarting IRb (or is this not possible).
• How can I configure IRb to load a bunch of source files "hello.rb" and "hello_objects.rb", i.e. at startup? I am heavily working in these and it would be nice to know a short hand to load these classes, without manually typing 'load' for each again.

Answer 1

I'm not sure it's possible to 'flush' a session. However, you can load your classes like this:

irb -r 'hello.rb' -r 'hello_objects.rb'

Answer 2

You can manage sessions in irb. Start irb and try this:

x=1
irb     # Opens a new session
puts x  # error
jobs    # lists sessions
quit    # kills current session
puts x  # 1

There is also the command "fg (number)" which switches between sessions. See: http://tagaholic.me/2009/05/11/demystifying-irb-commands.html

Answer 3

I believe what you're looking for is modifying your ~/.irbrc file. It was mentioned earlier, but no examples given. Here is a short example of requiring some common utilities you may want in your irb session:

# Print to yaml format with "y"
require 'yaml'
# Pretty printing
require 'pp'
# Ability to load rubygem modules
require 'rubygems'
# Tab completion
require 'irb/completion'

Answer 4

You can put any ruby code into your ~/.irbrc file, which will get evaluated whenever you run irb. In this case your require statements.

Answer 5

These are not direct answers but can apply to your desire to understand irb more.

A number of "irb" methods are available to the console object.

methods.grep(/irb/).sort
=> ["irb", "irb_bindings", "irb_cb", "irb_change_binding", "irb_change_workspace",
"irb_chws", "irb_context", "irb_current_working_binding", "irb_current_working_workspace",
"irb_cwb", "irb_cws", "irb_cwws", "irb_exit", "irb_fg", "irb_jobs", "irb_kill", "irb_load",
"irb_pop_binding", "irb_pop_workspace", "irb_popb", "irb_popws", "irb_print_working_binding",
"irb_print_working_workspace", "irb_push_binding", "irb_push_workspace", "irb_pushb",
"irb_pushws", "irb_pwb", "irb_pwws", "irb_quit", "irb_require", "irb_source", "irb_workspaces"]

Have some fun playing around with those.

Another is the "conf" object that gives feedback about your irb environment:

conf
=> conf.ap_name="irb"
conf.auto_indent_mode=false
conf.back_trace_limit=16
conf.debug_level=1
conf.echo=true
conf.ignore_eof=false
conf.ignore_sigint=true
conf.inspect_mode=nil
conf.io=#<IRB::StdioInputMethod:0x79da0>
conf.irb=#<IRB::Irb:0x7c58c>
conf.irb_name="irb"
conf.irb_path="(irb)"
conf.last_value=...
conf.line_no=6
conf.load_modules=[]
conf.prompt_c="%N(%m):%03n:%i* "
conf.prompt_i="%N(%m):%03n:%i> "
conf.prompt_mode=:DEFAULT
conf.prompt_s="%N(%m):%03n:%i%l "
conf.rc=true
conf.return_format="=> %s\n"
conf.thread=#<Thread:0x31790 run>
conf.use_readline=false
conf.verbose=nil
conf.workspace=#<IRB::WorkSpace:0x7aa84 @main=main, @binding=#<Binding:0x7a2a0>>