Is it possible to configure the IRB prompt to change dynamically?

Question

I'd like to navigate around the filesystem in IRB and have the prompt change to reflect the current working directory, but I can't figure out how to make the prompt update after each command. Ultimately I'd like to use IRB in day to day work a lot more and let bash slip away. I tried this in my .irbrc:

require 'fileutils'
include FileUtils

IRB.conf[:PROMPT][:CUSTOM] = {
    :PROMPT_N => "\e[1m:\e[m ",
    :PROMPT_I => "\e[1m#{pwd} >\e[m ",
    :PROMPT_S => "FOO",
    :PROMPT_C => "\e[1m#{pwd} >\e[m ",
    :RETURN => ""
}
IRB.conf[:PROMPT_MODE] = :CUSTOM

But the IRB prompt is not updated:

julianmann@mango:~ > irb
/users/julianmann > puts pwd
/users/julianmann
/users/julianmann > cd 'dev'
/users/julianmann > puts pwd
/users/julianmann/dev
/users/julianmann > 

I'd really like the prompt to change.

Slackjawed

Answer 1

Here's a quick hack to get the working dir. It's sort of fragile, but it worked on ruby 1.8.7 and 1.9.2.

Set your prompt string to something like this:

"%N(%m):%03n:%i %~> ".tap {|s| def s.dup; gsub('%~', Dir.pwd); end }

The "%~" directive is not understood by irb itself, so I used it to do the replacement. This hack relies on the fact that irb calls dup to generate the prompt.

Defelice

I'm looking at the docs for Object#tap and not quite understanding it yet but it looks like a powerful way to redefine methods inline. Love it! – Slackjawed

@julian-mann yep, tap is real useful. Careful though if you're using ruby < 1.8.7 without rails, because it doesn't have tap. – Defelice

a.tap { |i| ... } is basically i = a; ... ; a = i – Kovar

@Kovar Not exactly. tap doesn't: 1. reassign a at the end; 2. define assign any local variables in the enclosing scope. Rather, these 2 are equivalent - Tap: s="a"; s2="b"; s2.tap{|s| p "Inside: #{s}" }; p [s, s2] / Lambda: s="a"; s2="b"; lambda {|s| p "Inside: #{s}" }.call(s2); p [s, s2]. Notice how the block variable s doesn't overwrite the existing s outside the block. – Defelice

(I know it's an old thread) It lead me in the right direction, I made a new class class MyPrompt < String, then set the prompt to MyPrompt.new('some nice prompt'). And then I have a better control of the prompt and can override methods without disturbing the String class. – Shew

@Shew That's a good idea. (Note that my solution doesn't disturb the String class either; it redefines a method on a single String instance.) – Defelice

This doesn't work anymore with the latest IRB (v1.11.0 currently). I've posted another answer that works with the latest IRB: https://mcmap.net/q/1939273/-is-it-possible-to-configure-the-irb-prompt-to-change-dynamically – Rapt

Answer 2

Another option is to use fresh. It's based on the irb alternative ripl and also shows the current directory as its prompt :]

Wien

Thanks! Downloaded and its really cool, just what I was looking for. I was tempted by Rush too, but the docs say it has no concept of a current directory, that and the syntax put me off. The nice thing about fresh is that when I have my bash head on it behaves as expected (mostly) - navigating around is easy. And I when I want to do some ruby its right there. – Slackjawed

Answer 3

You have to run(alias) irb like so

irb --prompt custom

Or alternatively add IRB.conf[:PROMPT_MODE] = :CUSTOM to your .irbrc

P.S. This isn't an EXACT answer to your question. But you might try using RUSH.

It doesn't have the concept of a current working directory, but it is easily configurable.

Herrah

sorry - I should have mentioned that I did have RB.conf[:PROMPT_MODE] = :CUSTOM in .irbrc - I'll edit the question – Slackjawed

RUSH does indeed look pretty cool I'll check it out. Thanks!! – Slackjawed

Answer 4

Its kind of static though but have a look, it may help you IN Linux ( Ubuntu 14.04)

You can change the irritating prompt of the irb console just by following some simple steps

Open your terminal

goto the location /home/leapfrog/.rvm/scripts

$ cd ~/.rvm/scripts

Open the file ‘irbrc.rb’, use superuser power to over-write the

$ sudo gedit irbrc.rb

You can see a portion of code like this. Replace the former with latter codes

# Set up the prompt to be RVM specific.
#@prompt = {
# :PROMPT_I => "#{rvm_ruby_string} :%03n > ", # default prompt
# :PROMPT_S => "#{rvm_ruby_string} :%03n%l> ", # known continuation
# :PROMPT_C => "#{rvm_ruby_string} :%03n > ",
# :PROMPT_N => "#{rvm_ruby_string} :%03n?> ", # unknown continuation
# :RETURN => " => %s \n",
# :AUTO_INDENT => true
#}

@prompt = {
 :PROMPT_I => "ROR: %03n > ", # default prompt
 :PROMPT_S => "%03n%l> ", # known continuation
 :PROMPT_C => "%03n > ",
 :PROMPT_N => "%03n?> ", # unknown continuation
 :RETURN => " O/P => %s \n",
 :AUTO_INDENT => true
}

Just save the file and restart the irb console Further mode you can see this link https://cbabhusal.wordpress.com/2014/12/22/ruby-rvm-change-prompt-of-irb/

Humanize

Answer 5

If it may serve to contribute to the discussion, albeit belatedly: It may be possible to change the prompt after the IRB environment is initialized, such as via some values on IRB.conf[:MAIN_CONTEXT]

For a binding of c = IRB.conf[:MAIN_CONTEXT] the fields affecting prompt formatting may include the following

• c.prompt_c
• c.prompt_i
• c.prompt_n
• c.prompt_s
• c.return_format
• c.auto_indent_mode
• c.prompt_mode

An example in updating the prompt_i field directly:

irb(main):009:0> IRB.conf[:MAIN_CONTEXT].prompt_i="%N %m %i >>"
=> "%N %m %i >>"

irb main 0 >>

Outside of the set of formatting specifiers documented in the IRB module documentation (3.0.0) it may not be supported - at present - to use an expression that would be evaluated when the prompt is displayed, in IRB. Each of the prompt strings may be used as simply a literal format string.

With some limitations albeit, but it may be possible to update the IRB prompt after IRB is initialized.

Disclaimer: This is not guaranteed to update all state values related to the prompt, under IRB.conf[:MAIN_CONTEXT]

Executant

Answer 6

Kelvin's clever "quick hack" answer, which relied on dup, doesn't work anymore with the latest version of IRB (v1.11.0 right now).

Here's an alternative that allows providing a dynamic IRB prompt, which takes advantage of the fact that main.to_s is provided as %m in the IRB prompt configs:

# Save this file as `.irbrc`.
#
# Put it in your home directory to make it your default,
# or in a particular directory where you want it.
#
# Note: If you have an `.irbrc` in your home directory it
#       will take precedence over a local `.irbrc`.

# define `main.to_s` to provide dynamic context info.
# `main.to_s` is `%m` in the IRB prompt.
# `%m` is included in the default IRB prompt.
def self.to_s
  "#{Dir.pwd}"
end

# This should be the default already, but adding this line
# ensures you use an IRB prompt config that includes `%m`.
IRB.conf[:PROMPT_MODE] = :DEFAULT

Rapt