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

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.

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.

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 :]

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.

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/

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]