$ gem sources --add http://gemcutter.org
$ gem install irb_hacks
Add to your ~/.irbrc:
require "rubygems"
require "irb_hacks"
Now fire up IRB for a quick test:
$ irb
irb> ae
(snippet)>>
If you see "(snippet)", you're ready to go.
There's often a need to invoke our work-in-progress code a number of times using the same arguments, wrapping block, etc. For that, "code snippets" feature is quite handy.
irb_hacks gem provides the two methods with short, meaningless (and thus conflict-free) names -- a and ae. a means nothing, it's just the first letter of the alphabet. a invokes the last-edited snippet. ae lets you edit the actual snippet (it roughly stands for "a" + "edit").
A very basic example:
irb> ae
(snippet)>> puts "Hello, world"
irb> a
Hello, world
Snippet arguments are supported. It's an array called args in snippet context.
irb> ae
(snippet)>> p "args", args
irb> a 10, 1.0, "a string"
"args"
[10, 1.0, "a string"]
Snippets work just like normal Ruby methods -- they return the value of the last statement executed.
irb> ae
(snippet)>> ["alfa", "zulu", "bravo"] + args
irb> puts a("charlie").sort
alfa
bravo
charlie
zulu
Snippets support code blocks. It's a Proc called block in snippet context. Usage example follows (suppose we're building a simplistic /etc/passwd parser).
irb> ae
(snippet)>> File.readlines("/etc/passwd").map(&block).each {|s| p s}; nil
irb> a {|s| ar = s.split(":"); {:name => ar[0], :uid => ar[2]}}
{:uid=>"0", :name=>"root"}
{:uid=>"1", :name=>"bin"}
{:uid=>"2", :name=>"daemon"}
{:uid=>"3", :name=>"adm"}
...
Snippets are persistent though IRB invocations. That's quite handy, since not all stuff can be dynamically reloaded and sometimes we have to restart IRB to ensure a clean reload.
irb> ae
(snippet)>> puts "Snippets are persistent!"
irb> exit
$ irb
irb> a
Snippets are persistent!
Just in case, snippet history file is called .irb_snippet_history in your $HOME.
Snippets maintain their own Readline history. When you press [Up] and [Down] keys in ae, you browse the previously used snippets, not just your previous IRB input. Don't retype the snippet you used yesterday -- press [Up] a couple times and you'll see it.
irb> ae
(snippet)>> puts "snippet one"
irb> hala
irb> bala
irb> ae
(snippet)>> puts "snippet two"
irb> foo
irb> moo
irb> ae
(snippet)>>
## Pressing [Up] will give you...
(snippet)>> puts "snippet two"
## Pressing [Up] again will give you...
(snippet)>> puts "snippet one"
Sometimes the data your code works with is too long to fit in a console window. The clearest example of this are variables filled with text content, e.g. Hpricot documents/elements.
To solve that, the greatest paging program of all times, GNU less, comes to the rescue.
$ irb
irb> files = Dir["/etc/*"].sort
## Some bulky array...
irb> less files
## ... which we browse interactively :).
In block form, less hack intercepts everything output to STDOUT (and, optionally, to STDERR), and feeds it to the pager.
$ irb
irb> less do
puts "Hello, world"
end
Now with STDERR capture:
$ irb
irb> less(:stderr) do
puts "to stdout"
STDERR.puts "to stderr"
end
To specify another paging program or tweak less options, write in your ~/.irbrc:
IrbHacks.less_cmd = "more"
, or something else you find appropriate.
Send bug reports, suggestions and criticisms through project's page on GitHub.