Tiny IRB improvement - max-size of return format

I’m not sure if it’s appropriate to post here, but I found this very
useful, wanted to share it with people, and didn’t know where else.

So I use IRB (and script/console) a lot for testing out regexps or small
code blocks, inspecting running Rails apps, and so on. One thing that
can be very annoying is when you run a command like

IRB> a = File.read(“bigfile.txt”)

and IRB spits out the entire contents of the file. The same happens when
you do

user = User.find_by_name(“Stian”)

in script/console, and the whole user object is inspected, often with
his/her files, messages, permissions etc added in

As far as I know, there is only a way of turning this return off, but
not of limiting it. I tried turning it off, but found myself doing

IRB> MD5::md5(“Peter”)
IRB>

over and over, which was annoying. So I wrote this little patch:

diff -r …/1.8-stian/irb/context.rb ./irb/context.rb
37,38d36
< @max_output_size = (IRB.conf[:MAX_OUTPUT_SIZE] ?
IRB.conf[:MAX_OUTPUT_SIZE] : 500)
<
119d116
< attr_accessor :max_output_size
diff -r …/1.8-stian/irb.rb ./irb.rb
297c297
< text = sprintf @context.return_format,
@context.last_value.inspect

    printf @context.return_format, @context.last_value.inspect

299c299
< text = sprintf @context.return_format, @context.last_value

    printf @context.return_format, @context.last_value

301d300
< puts text[[email protected]_output_size]

works on both Ruby 1.8.4 and 1.8.6. Basically it adds a new conf. option

  • max_output_size, which defaults to 500, and restricts all results
    based on this. Note that you can still see the whole thing by p object,
    etc.

I just wanted to share it, because I found it very useful. And it’s neat
to be able to hack on “Ruby” itself, even in a tiny way :slight_smile:

thanks
Stian

Nice patch. Not to steal your thunder, but you can also mute irb’s
response by tacking on “; nil” to the end of a particularly noisy
return result:

a = IO.read(‘somebigfile’); nil
=> nil

a.scan(/blah/)
=> …

Stian H. wrote:

you do
IRB>
diff -r …/1.8-stian/irb.rb ./irb.rb
< puts text[[email protected]_output_size]
to be able to hack on “Ruby” itself, even in a tiny way :slight_smile:

thanks
Stian

Nice. You don’t have to patch the installed irb to do this, if you don’t
want to (maybe other users on your system will care, or maybe you don’t
have permissions). You can, instead, monkey patch irb using your .irbrc
file:

class IRB::Context
attr_accessor :max_output_size

alias initialize_before_max_output_size initialize
def initialize(*args)
initialize_before_max_output_size(*args)
@max_output_size = (IRB.conf[:MAX_OUTPUT_SIZE] ?
IRB.conf[:MAX_OUTPUT_SIZE] : 500)
end
end

class IRB::Irb
def output_value
text =
if @context.inspect?
sprintf @context.return_format, @context.last_value.inspect
else
sprintf @context.return_format, @context.last_value
end
max = @context.max_output_size
if text.size < max
puts text
else
puts text[[email protected]_output_size-1] + “…” + text[-2…-1]
end
end
end

END

I also added a tweak so that you see the last character of the string.
For example:

irb(main):001:0> a = [0]*10000
=> [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0…]

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