This question already has answers here:
What will give me something like ruby readline with a default value?
(6 answers)
Closed 6 years ago.
I am using to Ruby to write a small command line utility to search Pubmed. Right now, I prompt the user for a query and display the results, and the user has the option of appending to the query or entering an entirely new query. I would like to add the ability to edit the current query; i.e. the prompt should come pre-filled with an editable version of the previous query, like so:
Enter query: <PREVIOUS QUERY HERE>
It's easy enough to print out the previous query next to the prompt, but how do I make this output editable, as if the user had typed it herself?
#casper:
Thank you for the response Casper. I tried the code that you supplied below, and it does indeed work on its own. Strangely enough, it doesn't seem to work when I try to use it in a gem. My gem is called db_hippo. I added rb-readline as a dependency in my gemspec, and I put the extension to RbReadline in lib/db_hippo/rb-readline.rb
module DbHippo
module RbReadline
<CASPER'S EXTENSION HERE>
end
end
I wish to use the functionality in another submodule of DbHippo, DbHippo::Source. In DbHippo::Source I added at the top:
require 'rb-readline'
require 'db_hippo/rb-readline'
Then in one of the methods of DbHippo::Source, I have:
RbReadline.prefill_prompt(query)
query = Readline.readline("Query: ", true)
The query variable is definitely not empty, but for some reason in this context the prompt doesn't get prefilled. I also notice that if I put the extension in the same file (lib/db_hippo/rb-readline) without making it a submodule of DbHippo, I get the error: uninitialized constant DbHippo::Source::Readline (NameError) on the line:
query = Readline.readline("Query: ", true)
This all seems to have something to do with proper naming of modules, require statements, and gems. This is the first gem I've tried to build. Any idea what's going wrong here?
Maybe googlers will find this useful.
With plain Readline on Ruby 2.1 you could use:
def ask(prompt, default=nil)
if default
Readline.pre_input_hook = -> {
Readline.insert_text(default)
Readline.redisplay
# prevent re-trigger on every `readline`
Readline.pre_input_hook = nil
}
end
data = Readline.readline("#{prompt}: ")
return data.chomp
end
ask("MOAR...?", "COMPUTARS!") # displays: MOAR...? COMPUTARS!
At the prompt the text COMPUTARS! will be editable
You can do it with RbReadline:
require 'rubygems'
require 'rb-readline'
module RbReadline
def self.prefill_prompt(str)
#rl_prefill = str
#rl_startup_hook = :rl_prefill_hook
end
def self.rl_prefill_hook
rl_insert_text #rl_prefill if #rl_prefill
#rl_startup_hook = nil
end
end
RbReadline.prefill_prompt("Previous query")
str = Readline.readline("Enter query: ", true)
puts "You entered: #{str}"
Related
I would like to know whether I can get source code a method on the fly, and whether I can get which file is this method in.
like
A.new.method(:a).SOURCE_CODE
A.new.method(:a).FILE
Use source_location:
class A
def foo
end
end
file, line = A.instance_method(:foo).source_location
# or
file, line = A.new.method(:foo).source_location
puts "Method foo is defined in #{file}, line #{line}"
# => "Method foo is defined in temp.rb, line 2"
Note that for builtin methods, source_location returns nil. If want to check out the C source code (have fun!), you'll have to look for the right C file (they're more or less organized by class) and find the rb_define_method for the method (towards the end of the file).
In Ruby 1.8 this method does not exist, but you can use this gem.
None of the answers so far show how to display the source code of a method on the fly...
It's actually very easy if you use the awesome 'method_source' gem by John Mair (the maker of Pry):
The method has to be implemented in Ruby (not C), and has to be loaded from a file (not irb).
Here's an example displaying the method source code in the Rails console with method_source:
$ rails console
> require 'method_source'
> I18n::Backend::Simple.instance_method(:lookup).source.display
def lookup(locale, key, scope = [], options = {})
init_translations unless initialized?
keys = I18n.normalize_keys(locale, key, scope, options[:separator])
keys.inject(translations) do |result, _key|
_key = _key.to_sym
return nil unless result.is_a?(Hash) && result.has_key?(_key)
result = result[_key]
result = resolve(locale, _key, result, options.merge(:scope => nil)) if result.is_a?(Symbol)
result
end
end
=> nil
See also:
https://rubygems.org/gems/method_source
https://github.com/banister/method_source
http://banisterfiend.wordpress.com/
Here is how to print out the source code from ruby:
puts File.read(OBJECT_TO_GET.method(:METHOD_FROM).source_location[0])
Without dependencies
method = SomeConstant.method(:some_method_name)
file_path, line = method.source_location
# puts 10 lines start from the method define
IO.readlines(file_path)[line-1, 10]
If you want use this more conveniently, your can open the Method class:
# ~/.irbrc
class Method
def source(limit=10)
file, line = source_location
if file && line
IO.readlines(file)[line-1,limit]
else
nil
end
end
end
And then just call method.source
With Pry you can use the show-method to view a method source, and you can even see some ruby c source code with pry-doc installed, according pry's doc in codde-browing
Note that we can also view C methods (from Ruby Core) using the
pry-doc plugin; we also show off the alternate syntax for show-method:
pry(main)> show-method Array#select
From: array.c in Ruby Core (C Method):
Number of lines: 15
static VALUE
rb_ary_select(VALUE ary)
{
VALUE result;
long i;
RETURN_ENUMERATOR(ary, 0, 0);
result = rb_ary_new2(RARRAY_LEN(ary));
for (i = 0; i < RARRAY_LEN(ary); i++) {
if (RTEST(rb_yield(RARRAY_PTR(ary)[i]))) {
rb_ary_push(result, rb_ary_elt(ary, i));
}
}
return result;
}
I created the "ri_for" gem for this purpose
>> require 'ri_for'
>> A.ri_for :foo
... outputs the source (and location, if you're on 1.9).
GL.
-r
Internal methods don't have source or source location (e.g. Integer#to_s)
require 'method_source'
User.method(:last).source
User.method(:last).source_location
I had to implement a similar feature (grab the source of a block) as part of Wrong and you can see how (and maybe even reuse the code) in chunk.rb (which relies on Ryan Davis' RubyParser as well as some pretty funny source file glomming code). You'd have to modify it to use Method#source_location and maybe tweak some other things so it does or doesn't include the def.
BTW I think Rubinius has this feature built in. For some reason it's been left out of MRI (the standard Ruby implementation), hence this hack.
Oooh, I like some of the stuff in method_source! Like using eval to tell if an expression is valid (and keep glomming source lines until you stop getting parse errors, like Chunk does)...
I have searched several questions/answers/blogs without success. How to remove/delete duplicate commands from irb history?
Ideally I want to have the same behavior I configured for my bash. That is: after I execute a command every other entry in the history with the exactly same command is deleted.
But it would already be good to eliminate duplicates when I close irb.
My current .irbrc:
require 'irb/ext/save-history'
IRB.conf[:SAVE_HISTORY] = 1000
IRB.conf[:HISTORY_FILE] = "#{ENV['HOME']}/.irb_history"
IRB.conf[:AUTO_INDENT] = true
Note: Ruby 2.4.1 (or newer!)
An AT_EXIT hook is a perfectly acceptable way to do this. Though monkey patching is not needed. IRB provides facilities for doing this by creating your own input method.
IRB gets its input from an InputMethod. History is provided by the
ReadlineInputMethod, which is a subclass.
InputMethods are attached to a Context. Entering conf in an irb session will give you access to the current context.
irb will read input according to the current context's io. For example:
irb [2.4.0] (screenstaring.com)$ conf.io
=> #<HistoryInputMethod:0x007fdc3403e180 #file_name="(line)", #line_no=3, #line=[nil, "4317.02 - 250 \n", "conf.id\n", "conf.io\n"], #eof=false, #stdin=#<IO:fd 0>, #stdout=#<IO:fd 1>, #prompt="irb [2.4.0] (screenstaring.com)$ ", #ignore_settings=[], #ignore_patterns=[]>
Uses my Bash-like history control class (for more info see below).
You can set conf.io to anything that conforms to the InputMethod interface:
conf.io = MyInputMethod.new
Whatever MyInputMethod#gets returns will be evaluated by IRB. Typically it reads from stdin.
To tell IRB to use your InputMethod at startup you can set the :SCRIPT config option:
# .irbrc
IRB.conf[:SCRIPT] = MyInputMethod.new
IRB will use :SCRIPT's value as input method when creating a Context. This can be set to a file to use its contents as the input method.
By default it's nil, which results in stdin being used (via Readline, if it's available).
To create an input method that ignores duplicates override ReadlineInputMethod#gets:
class MyInputMethod < IRB::ReadlineInputMethod
def gets
line = super # super adds line to HISTORY
HISTORY.pop if HISTORY[-1] == HISTORY[-2]
line
end
end
The InputMethod defined in my .irbrc allows one to set IRB_HISTCONTROL or IRB_HISTIGNORE like you would (more or less) for Bash:
IRB_HISTIGNORE=ignoreboth IRB_HISTCONTROL='\Aq!:foo' irb
This does the following:
Entries beginning with a space or duplicate (back-to-back) entries will not be added to the history
Entries beginning with q! (a custom method of mine) or containing foo will not be added to history
This will eliminate duplicates after closing IRB console. But it works only for IRBs using Readline (mac users warned).
# ~/.irbrc
require 'irb/ext/save-history'
IRB.conf[:SAVE_HISTORY] = 1000
IRB.conf[:HISTORY_FILE] = "#{ENV['HOME']}/.irb_history"
deduplicate_history = Proc.new do
history = Readline::HISTORY.to_a
Readline::HISTORY.clear
history.reverse!.uniq!
history.reverse!.each{|entry| Readline::HISTORY << entry}
end
IRB.conf[:AT_EXIT].unshift(deduplicate_history)
And this monkey patch will eliminate duplicates on the fly if your IRB is using Readline:
require 'irb/ext/save-history'
IRB.conf[:SAVE_HISTORY] = 1000
IRB.conf[:HISTORY_FILE] = "#{ENV['HOME']}/.irb_history"
class IRB::ReadlineInputMethod
alias :default_gets :gets
def gets
if result = default_gets
line = result.chomp
history = HISTORY.to_a
HISTORY.clear
history.each{|entry| HISTORY << entry unless entry == line}
HISTORY << line
end
result
end
end
Any suggestion on how to improve it?
This question already has answers here:
What will give me something like ruby readline with a default value?
(6 answers)
Closed 6 years ago.
Let's say I have the following code in Ruby:
print("Enter a filename:")
editableprint("untitled.txt")
filename = gets.chomp!
What would be the function "editableprint" so that "untitled.txt" is part of the input of the user for the gets function? (thus the user can edit the "untitled.txt" string or simply leave it as is")
There are similar questions here and here
However, the solutions there don't seem to work as expected, so it looks this is ruby version or platform dependent?
For example, this does not work for me, but also does not throw an error.
require "readline"
filename = Readline.insert_text("untitled.txt").readline("Enter a filename:")
print filename
But since it looks much better, and should work according to the documentation for ruby >= 2, I am leaving it there for now.
The following works on my system (ruby 2.3.1, OS X)
require "readline"
require 'rb-readline'
module RbReadline
def self.prefill_prompt(str)
#rl_prefill = str
#rl_startup_hook = :rl_prefill_hook
end
def self.rl_prefill_hook
rl_insert_text #rl_prefill if #rl_prefill
#rl_startup_hook = nil
end
end
RbReadline.prefill_prompt("untitled.txt")
str = Readline.readline("Enter a filename:", true)
puts "You entered: #{str}"
I would use vim to edit the file. Vim will save edited files in ~/.viminfo. The last edited file is marked with '0. The pattern of a file entry is 'N N N filename where N stands for a integer.
def editableprint(filename)
system "vi #{filename}"
regex = /(?<='0\s{2}\d\s{2}\d\s{2}).*/
viminfo = File.expand_path("~/.viminfo")
File.read(viminfo).scan(regex).first
end
In order to make this to work you would have to change your code
print("Enter a filename:")
filename = gets.chomp!
filename = "untitled.txt" if filename.emtpy?
edited_filename = editableprint("untitled.txt")
I would like to know whether I can get source code a method on the fly, and whether I can get which file is this method in.
like
A.new.method(:a).SOURCE_CODE
A.new.method(:a).FILE
Use source_location:
class A
def foo
end
end
file, line = A.instance_method(:foo).source_location
# or
file, line = A.new.method(:foo).source_location
puts "Method foo is defined in #{file}, line #{line}"
# => "Method foo is defined in temp.rb, line 2"
Note that for builtin methods, source_location returns nil. If want to check out the C source code (have fun!), you'll have to look for the right C file (they're more or less organized by class) and find the rb_define_method for the method (towards the end of the file).
In Ruby 1.8 this method does not exist, but you can use this gem.
None of the answers so far show how to display the source code of a method on the fly...
It's actually very easy if you use the awesome 'method_source' gem by John Mair (the maker of Pry):
The method has to be implemented in Ruby (not C), and has to be loaded from a file (not irb).
Here's an example displaying the method source code in the Rails console with method_source:
$ rails console
> require 'method_source'
> I18n::Backend::Simple.instance_method(:lookup).source.display
def lookup(locale, key, scope = [], options = {})
init_translations unless initialized?
keys = I18n.normalize_keys(locale, key, scope, options[:separator])
keys.inject(translations) do |result, _key|
_key = _key.to_sym
return nil unless result.is_a?(Hash) && result.has_key?(_key)
result = result[_key]
result = resolve(locale, _key, result, options.merge(:scope => nil)) if result.is_a?(Symbol)
result
end
end
=> nil
See also:
https://rubygems.org/gems/method_source
https://github.com/banister/method_source
http://banisterfiend.wordpress.com/
Here is how to print out the source code from ruby:
puts File.read(OBJECT_TO_GET.method(:METHOD_FROM).source_location[0])
Without dependencies
method = SomeConstant.method(:some_method_name)
file_path, line = method.source_location
# puts 10 lines start from the method define
IO.readlines(file_path)[line-1, 10]
If you want use this more conveniently, your can open the Method class:
# ~/.irbrc
class Method
def source(limit=10)
file, line = source_location
if file && line
IO.readlines(file)[line-1,limit]
else
nil
end
end
end
And then just call method.source
With Pry you can use the show-method to view a method source, and you can even see some ruby c source code with pry-doc installed, according pry's doc in codde-browing
Note that we can also view C methods (from Ruby Core) using the
pry-doc plugin; we also show off the alternate syntax for show-method:
pry(main)> show-method Array#select
From: array.c in Ruby Core (C Method):
Number of lines: 15
static VALUE
rb_ary_select(VALUE ary)
{
VALUE result;
long i;
RETURN_ENUMERATOR(ary, 0, 0);
result = rb_ary_new2(RARRAY_LEN(ary));
for (i = 0; i < RARRAY_LEN(ary); i++) {
if (RTEST(rb_yield(RARRAY_PTR(ary)[i]))) {
rb_ary_push(result, rb_ary_elt(ary, i));
}
}
return result;
}
I created the "ri_for" gem for this purpose
>> require 'ri_for'
>> A.ri_for :foo
... outputs the source (and location, if you're on 1.9).
GL.
-r
Internal methods don't have source or source location (e.g. Integer#to_s)
require 'method_source'
User.method(:last).source
User.method(:last).source_location
I had to implement a similar feature (grab the source of a block) as part of Wrong and you can see how (and maybe even reuse the code) in chunk.rb (which relies on Ryan Davis' RubyParser as well as some pretty funny source file glomming code). You'd have to modify it to use Method#source_location and maybe tweak some other things so it does or doesn't include the def.
BTW I think Rubinius has this feature built in. For some reason it's been left out of MRI (the standard Ruby implementation), hence this hack.
Oooh, I like some of the stuff in method_source! Like using eval to tell if an expression is valid (and keep glomming source lines until you stop getting parse errors, like Chunk does)...
I would like to change the name of the ruby process that gets displayed in the linux/unix top command. I have tried the
$0='miname'
approach but it only works with the ps command and in top the process keeps getting displayed as "ruby"
Dave Thomas had an interesting post on doing this in rails. There's nothing rails specific about the actual process name change code. He uses the $0='name' approach. When I followed his steps the name was changed in ps and top.
In the post he suggests using the c keyboard command if your version of top doesn't show the short version of the command by default.
Ruby 2.1 introduced a Process.setproctitle method for this purpose:
Process.setproctitle("My new title")
I don't think Ruby has the facility builtin (setproctitle(3)). You should probably try to look at ruby-ffi and create the interface to setproctitle(3).
EDIT: I know you have your answer but I want to show you some code to use ffi:
require "ffi"
#
module LibC
extend FFI::Library
attach_function :setproctitle, [:string, :varargs], :void
end
LibC.setproctitle("Ruby: executing %s", :string, $0)
Does not work on OS X because setproctitle(3) does not exist, works on FreeBSD.
The $0 = 'Foo' method works -- but many versions of top will require you to toggle command-line mode on with 'c'. We this very method here with rails and CentOS. Works a treat
I had a similar problem, updated the technique from the Dave Thomas post a little by putting it in a rack middleware, rather than the before/after pattern.
Put this in lib/rack/set_process_title.rb:
# Set the process title to the URI being processed
#- useful for debugging slow requests or those that get stuck
class Rack::SetProcessTitle
def initialize(app)
#app = app
end
def call(env)
$0 = env['REQUEST_URI'][0..80]
#status, #headers, #response = #app.call(env)
$0 = env['REQUEST_URI'][0..80] + '*'
[#status, #headers, #response]
end
end
... and this goes at the end of config/environment.rb:
Rails.configuration.middleware.insert_after Rack::Lock, Rack::SetProcessTitle
More words in the blog post: http://blog.actbluetech.com/2011/06/set-your-process-name-in-top-and-ps.html
I know Keltia already posted something very similar, but Linux doesn't have setproctitle(3).
Linux has had this functionality in prctl() since version 2.6.9.
I used Fiddle/DL since they are included by default with Ruby.
require("fiddle")
def set_process_name_linux(name)
Fiddle::Function.new(
Fiddle::Handle["prctl".freeze], [
Fiddle::TYPE_INT, Fiddle::TYPE_VOIDP,
Fiddle::TYPE_LONG, Fiddle::TYPE_LONG,
Fiddle::TYPE_LONG
], Fiddle::TYPE_INT
).call(15, name, 0, 0, 0)
end
def set_process_name_unknown(name)
warn("No implementation for this OS.".freeze)
end
def set_process_name(name)
case RUBY_PLATFORM.split("-".freeze)[1]
when "linux".freeze
set_process_name_linux(name)
else
set_process_name_unknown(name)
end
end
From #jessehz answer, following code work perfect on my linux X86_64.
Ruby 1.9.3, 2.0, 2.1, 2.2, 2.3 is tested.
It will change the output in ps top command.
It can be kill or signal with pkill, pgrep, killall.
Perfect!
def set_process_name_linux(name)
handle = defined?(DL::Handle) ? DL::Handle : Fiddle::Handle
Fiddle::Function.new(
handle['prctl'.freeze], [
Fiddle::TYPE_INT, Fiddle::TYPE_VOIDP,
Fiddle::TYPE_LONG, Fiddle::TYPE_LONG,
Fiddle::TYPE_LONG
], Fiddle::TYPE_INT
).call(15, name, 0, 0, 0)
$PROGRAM_NAME = name
end
set_process_name_linux('dummy')