## Question:

Before downloading file, I need to set up a way it (the .csv typically, but not always) will be parsed.

I don't want to download the whole file especially if the "headers" do not match what is expected.

Is there a way to only download up until a certain number of byes and then gracefully kill the connection?

There's no explicit support for this in an FTP protocol.

There's an expired draft for RANG command that would allow this:
https://tools.ietf.org/html/draft-bryan-ftp-range-08
But that's obviously supported by only new FTP servers.

Though there's nothing that prevents you from initiating a normal (full) download and forcefully break it as soon you get the amount of data you need.

All you need to do is to close the data transfer connection. This is basically what all FTP clients do, when an end user decides to abort the transfer.

This approach might result in few error messages in an FTP server log.

If you can use an SFTP protocol, then it's easy. The SFTP supports this natively.

# Related:

## For loop with flexible stop variable

ruby
I need to write a loop for x in (1..y) where the y variable can be changed somehow. How can I do that? For example: for x in (1..y/x) But it does not work. ...

ruby-on-rails,ruby,rest,activerecord,one-to-many
I'm creating a rails application that is a backend for a mobile application. The backend is implemented with a RESTful web API. Currently I am trying to add gamification to the platform through the use of badges that can be earned by the user. Right now the badges are tied...

## Rails less url path change

ruby-on-rails,ruby,url,path,less
Developing a Rails application with the less-rails gem I found something unusual : // app/assets/common/css/desktop/typo.less @font-face{ font-family:'SomeFont'; src:url("fonts/db92e416-da16-4ae2-a4c9-378dc24b7952.eot?#iefix"); // ... } The requested font is app/assets/common/css/fonts/db92e416-da16-4ae2-a4c9-378dc24b7952.eot This font is compiled with less and the results is : @font-face { font-family: 'SomeFont'; src: url("desktop/fonts/db92e416-da16-4ae2-a4c9-378dc24b7952.eot?#iefix"); //... } Do you know why is...

## Keep leading zeroes when converting string to integer

ruby
For no particular reason, I am trying to add a #reverse method to the Integer class: class Integer def reverse self.to_s.reverse.to_i end end puts 1337.reverse # => 7331 puts 1000.reverse # => 1 This works fine except for numbers ending in a 0, as shown when 1000.reverse returns 1 rather...

## Call method to generate arguments in ruby works in 1.8.7 but not 1.9.3

ruby-on-rails,ruby,ruby-1.9.3
This is something that I had working in ruby 1.8.7, but no longer works in 1.9.3, and I am not sure what changes make this fail. Previously, I had something like this myFunction(submitArgs()) where submitArgs was a helper method that could be called with some options def submitArgs(args={}) #Some logic/manipulations...

## Saying there are 0 arguments when I have 2? Trying to open a CSV file to write into

ruby,file,csv,dir
I'm trying to read from a CSV file and codify people into groups using an equation. I append the name of their group they fall into to the end of the array that their row creates. Then I write it to a new file so I don't overwrite the original...

## Using Ruby Pathname to access relative directory

ruby,path,pathname
Given I have a relative path pointing to a directory how can I use it with Ruby's Pathname or File library to get the directory itself? p = Pathname.new('dir/') p.dirname => . p.directory? => false I have tried './dir/', 'dir/', 'dir'. What I want is p.dirname to return 'dir'. I...

## Ruby access words in string

ruby
I don't understand the best method to access a certain word by it's number in a string. I tried using [] to access a word but instead it returns letter. puts s # => I went for a walk puts s[3] # => w ...

Okay, I've been trying to figure this out for a few hours and it's starting to kill me. I wrote a primitive version checker for an app I work on every once and awhile. It's just a simple for fun project. The version checker has been a pain though. It...

## Heroku rake db:migrate failing - uninitialized constant

ruby-on-rails,ruby,heroku
My app is working fine locally and my push to Heroku was successful. But, when I run heroku run rake db:migrate, I get the following error: NameError: uninitialized constant AddWeightToExercises Here is the failed migration: class AddWeightToExercise < ActiveRecord::Migration def change add_column :exercises, :weight, :float end end edit: Thanks for...

## .split and regular expression in Ruby

ruby,regex
I want to split my string by (',') but ignore ',' if they are inside quotes. For example " 2,2,4,'hello', 'world', 'hi, there' " I want to split it so 'hi, there' will not be split into two different array elements in ruby. How can I do that? Probably use...

## How to get return value from a forked / spawned process in Ruby?

ruby,process,output,fork,spawn
My simple test program: pid = Process.spawn("sleep 10;date") How can I place the output (eg stdout) of the "date" command in a variable when it is available? I don't want to use a file for the data exchange....

## Error when trying to install app with mysql2 gem

mysql,ruby-on-rails,ruby,ruby-on-rails-4
Im trying to install an open source rails 3.2.21 application that uses the mysql2 gem, but when i try and run the bundle commant I get the following error: Fetching: mysql2-0.3.18.gem (100%) Building native extensions. This could take a while... p ERROR: Error installing mysql2: ERROR: Failed to build gem...

## Ruby: How to copy the multidimensional array in new array?

ruby-on-rails,arrays,ruby,multidimensional-array
seating_arrangement [ [:first, :second, :none], [:first, :none, :second], [:second, :second, :first], ] I need to copy this array into new array. I tried to do it by following code: class Simulator @@current_state def initialize(seating_arrangement) @@current_state = seating_arrangement.dup end But whenever I am making any changes to seating_arrangement current_state changes automatically....

## Appending an element to a page in VoltRb

html,ruby,opalrb,voltrb

## How to flatten a structure of embedded Set and Hash

ruby,recursion
I would like to convert an embedding structure into a flat one. An embedding structure is a set of 0 or more objects, such as: a string or a hash having some string as key and some other embedding structure as value. A flat structure is a set of arrays...

## Can't map a range of dates in Ruby/Rails

ruby-on-rails,ruby
I'm trying to map a range of dates and pass them to my view as an array, as follows: from, to = Date.parse("2014-01-01"), Date.yesterday date_range = (from..to) @mapped_dates = date_range.map {|date| date.strftime("%b %e")} I reference them in some JS in my view as follows: dateLabels = <%= raw @mapped_dates.to_json %>;...

## What is Rack::Utils.multipart_part_limit within Rails and what function does it perform?

ruby-on-rails,ruby,rack,multipart
Rack::Utils.multipart_part_limit is set to 128 by default. What purpose does the value have and what effect does it have within the Rails system?...

## How to pivot array into another array in Ruby

arrays,ruby,csv
I have a multidimensional array like this one : myArray = [["Alaska","Rain","3"],["Alaska","Snow","4"],["Alabama","Snow","2"],["Alabama","Hail","1"]] I would like to end up with CSV output like this. State,Snow,Rain,Hail Alaska,4,3,nil Alabama,2,nil,1 I know that to get this outputted to CSV the way I want it I have to have output array like this: outputArray =[["State","Snow","Rain","Hail"],["Alaska",4,3,nil],["Alabama",2,nil,1]]...

## Iterating over EncryptedDataBagItem in Chef Recipe

ruby,json,chef,devops
I would like to decrypt a chef data bag item (named passwords) and store all of its attributes in a temporary JSON file which is read (and then deleted) by a node.js app. Is there a way to iterate over attributes of a data bag ITEM and get their values?...

## Rails shared controller actions

ruby-on-rails,ruby,ruby-on-rails-4
I am having trouble building a controller concern. I would like the concern to extend the classes available actions. Given I have the controller 'SamplesController' class SamplesController < ApplicationController include Searchable perform_search_on(Sample, handle: [ClothingType, Company, Collection, Color]) end I include the module 'Searchable' module Searchable extend ActiveSupport::Concern module ClassMethods def...

## Get X days out of an Array

ruby,ruby-on-rails-4
I have an array filled with Datetime objects: [Mon, 22 Jun 2015, Tue, 23 Jun 2015, Wed, 24 Jun 2015, Thu, 25 Jun 2015, Fri, 26 Jun 2015, Sat, 27 Jun 2015, Sun, 28 Jun 2015] I know how to select what I want from the array ex: week.select{|x|x.monday? ||...

## Rails - link_to path based on object's name + refactoring multiple custom actions

ruby-on-rails,ruby,refactoring
I'm looking to simplify the link_to path based on thr object's name and also am looking into refactoring multiple custom actions. I've managed to get this working below. <% ServiceMenu.all.each do |menu| %> <tr class=" <%= cycle('odd', 'even') %>"> <td><%= link_to menu.name, ("tech/""#{menu.name.parameterize}") %></td> </tr> <% end %> I feel...

## Seeding fails validation for nested tables (validates_presence_of)

ruby-on-rails,ruby,validation,ruby-on-rails-4,associations
An Organization model has a 1:many association with a User model. I have the following validation in my User model file: belongs_to :organization validates_presence_of :organization_id, :unless => 'usertype==1' If usertype is 1, it means the user will have no organization associated to it. For a different usertype the presence of...

## How could I padding spaces to a fix length

ruby
I need all strings' length with 5 Original [477, 4770,] Expected ["477 ", "4770 "] How could I do it with Ruby ?...

## Same enum values for multiple columns

ruby-on-rails,ruby,enums
I need to do something like this: class PlanetEdge < ActiveRecord::Base enum :first_planet [ :earth, :mars, :jupiter] enum :second_planet [ :earth, :mars, :jupiter] end Where my table is a table of edges but each vertex is an integer. However, it seems the abvove is not possible in rails. What might...

## rails - NameError (undefined local variable or method while using has_many :through

ruby-on-rails,ruby,ruby-on-rails-4
My rails app gives following error: NameError (undefined local variable or method 'fac_allocs' for #): app/models/room.rb:4:in '' app/models/room.rb:1:in '' app/controllers/rooms_controller.rb:3:in 'index' room.rb file class Room < ActiveRecord::Base has_many :bookings has_many :fac_allocs has_many :facs, :through => fac_allocs end ...

## Ruby gsub group parameters do not work when preceded by escaped slashes

ruby,regex
I am trying to perform a trivial substitution, that in any other language I have come across, work as per the documentation. However, my substitution fails for some reason. The documentation examples list: "hello".gsub(/[aeiou]/, '*') #=> "h*ll*" "hello".gsub(/([aeiou])/, '<\1>') #=> "h<e>ll<o>" "hello".gsub(/./) {|s| s.ord.to_s + ' '} #=> "104 101...

## regex to pull in number with decimal or comma

ruby,regex
This is my line of code: col_value = line_item[column].scan(/\d+./).join().to_i When I enter 30,000 into the textfield, col_value is 30. I want it to bring in any number: 30,000 30.5 30.55 30000 Any of these are valid... Is there a problem with the scan and or join which would cause it...

## Get value from string representing local variable [duplicate]

ruby,local-variables
This question already has an answer here: Is there a 'variable_get' method? If not, how can I create my own? 2 answers I have a local variable name as a string, and need to get its value. variable = 22 "variable".to_variable? How can I get the value 22 form...

## On rendering from controller, current_page method does not seem to work

ruby-on-rails,ruby,ruby-on-rails-4,model-view-controller
I have a navigation bar included in application.html.erb. Because for some pages, such as the signup page, I need to place additional code inside the navigation bar, I have excluded those pages for showing the navigation bar through application.html.erb and instead included it in their respective view pages. See code...

## Loop until i get correct user

ruby,redis
I have users stored in Redis and want to be able to call only certain subsets from a set, if i don't get the correct user back i want to put it back in the set and then try again until i get one of the desired users @redis =...

## Ruby boolean logic: some amount of variables are true

ruby
Let say I have 3 variables: a, b, c. How can I check that just zero or one of them is true?...

## Dividing by half in ruby to create an effective calculator

ruby,calculator
For the past while I've been working on a calculator, but have run into problems when needing to divide by a half. I'll add the offending bit of code along with a loop to keep it open below. on = true while on == true do half = 1.0 /...