Curb - Libcurl bindings for Ruby

Curb (probably CUrl-RuBy or something) provides Ruby-language bindings for the
libcurl(3), a fully-featured client-side URL transfer library.
cURL and libcurl live at https://curl.se/libcurl/ .

Curb is a work-in-progress, and currently only supports libcurl’s easy and multi modes.

A big advantage to Curb over all other known ruby http libraries is it’s ability to handle timeouts without the use of threads.

License

Curb is copyright © 2006 Ross Bamford, and released under the terms of the
Ruby license. See the LICENSE file for the gory details.

Easy mode

GET request

  res = Curl.get("https://www.google.com/") {|http|
    http.timeout = 10 # raise exception if request/response not handled within 10 seconds
  }
  puts res.code
  puts res.head
  puts res.body

POST request

  res = Curl.post("https://your-server.com/endpoint", {post: "this"}.to_json) {|http|
    http.headers["Content-Type"] = "application/json"
  }
  puts res.code
  puts res.head
  puts res.body

FTP Support

require ‘curb’

Basic FTP Download

puts "=== FTP Download Example ==="
ftp = Curl::Easy.new('ftp://ftp.example.com/remote/file.txt')
ftp.username = 'user'
ftp.password = 'password'
ftp.perform
puts ftp.body

FTP Upload

puts "\n=== FTP Upload Example ==="
upload = Curl::Easy.new('ftp://ftp.example.com/remote/upload.txt')
upload.username = 'user'
upload.password = 'password'
upload.upload = true
upload.put_data = File.read('local_file.txt')
upload.perform

List Directory Contents

puts "\n=== FTP Directory Listing Example ==="
list = Curl::Easy.new('ftp://ftp.example.com/remote/directory/')
list.username = 'user'
list.password = 'password'
list.set(:dirlistonly, 1)
list.perform
puts list.body

FTP over HTTP proxy tunnel (NLST/LIST)

When listing directories through an HTTP proxy with proxy_tunnel (CONNECT), let libcurl manage the passive data connection. Do not send PASV/EPSV or NLST via easy.ftp_commands — QUOTE commands run on the control connection and libcurl will not open the data connection, resulting in 425 errors.

To get NLST-like output safely:

list = Curl::Easy.new('ftp://ftp.example.com/remote/directory/')
list.username = 'user'
list.password = 'password'
list.proxy_url = 'http://proxy.example.com:80'
list.proxy_tunnel = true

# Ask libcurl to perform a listing (names only)
list.set(:dirlistonly, 1)

# If the proxy or server has trouble with EPSV/EPRT, you can adjust:
# list.set(:ftp_use_epsv, 0)       # disable EPSV
# list.set(:ftp_use_eprt, 0)       # disable EPRT (stick to IPv4 PASV)
# list.set(:ftp_skip_pasv_ip, 1)   # ignore PASV host, reuse control host

list.perform
puts list.body

If you need a full LIST output instead of just names, omit dirlistonly and parse the server response accordingly. The key is to let libcurl initiate the data connection (PASV/EPSV) instead of trying to drive it via ftp_commands.

Full LIST directory listing

To retrieve the full LIST output (permissions, owner, size, timestamp, name), simply do not set dirlistonly:

list = Curl::Easy.new('ftp://ftp.example.com/remote/directory/')
list.username = 'user'
list.password = 'password'

# Explicitly ensure names+metadata (LIST) rather than NLST
# list.set(:dirlistonly, 0) # optional; default is LIST for directory URLs

list.perform
puts list.body # multi-line LIST output

Through an HTTP proxy tunnel, the same considerations apply as the NLST example above — just omit dirlistonly and keep the optional EPSV/EPRT/PASV tweaks if needed:

list = Curl::Easy.new('ftp://ftp.example.com/remote/directory/')
list.username = 'user'
list.password = 'password'
list.proxy_url = 'http://proxy.example.com:80'
list.proxy_tunnel = true

# Optional tweaks if the proxy/server combination struggles
# list.set(:ftp_use_epsv, 0)
# list.set(:ftp_use_eprt, 0)
# list.set(:ftp_skip_pasv_ip, 1)

list.perform
puts list.body

Advanced FTP Usage with Various Options

puts "\n=== Advanced FTP Example ==="
advanced = Curl::Easy.new do |curl|
  curl.url = 'ftp://ftp.example.com/remote/file.txt'
  curl.username = 'user'
  curl.password = 'password'

  # FTP Options
  curl.ftp_response_timeout = 30
  curl.ftp_create_missing_dirs = true   # Create directories if they don't exist
  curl.ftp_filemethod = Curl::CURL_MULTICWD  # Use multicwd method for traversing paths

  # SSL/TLS Options for FTPS
  curl.use_ssl = Curl::CURLUSESSL_ALL  # Use SSL/TLS for control and data
  curl.ssl_verify_peer = true
  curl.ssl_verify_host = true
  curl.cacert = "/path/to/cacert.pem"

  # Progress callback
  curl.on_progress do |dl_total, dl_now, ul_total, ul_now|
    puts "Download: #{dl_now}/#{dl_total} Upload: #{ul_now}/#{ul_total}"
    true # must return true to continue
  end

  # Debug output
  curl.verbose = true
  curl.on_debug do |type, data|
    puts "#{type}: #{data}"
    true
  end
end

advanced.perform

Parallel FTP Downloads

puts "\n=== Parallel FTP Downloads Example ==="
urls = [
  'ftp://ftp.example.com/file1.txt',
  'ftp://ftp.example.com/file2.txt',
  'ftp://ftp.example.com/file3.txt'
]

Common options for all connections

options = {
  :username =&gt; 'user',
  :password =&gt; 'password',
  :timeout =&gt; 30,
  :on_success =&gt; proc { |easy| puts "Successfully downloaded: #{easy.url}" },
  :on_failure =&gt; proc { |easy, code| puts "Failed to download: #{easy.url} (#{code})" }
}

Curl::Multi.download(urls, options) do |curl, file_path|
  puts "Completed downloading to: #{file_path}"
end

You will need

A working Ruby installation (2.0.0+ will work but 2.1+ preferred) (it’s possible it still works with 1.8.7 but you’d have to tell me if not…)
A working libcurl development installation (Ideally one of the versions listed in the compatibility chart below that maps to your curb version)
A sane build environment (e.g. gcc, make)

Version Compatibility chart

A non-exhaustive set of compatibility versions of the libcurl library
with this gem are as follows. (Note that these are only the ones that have been
tested and reported to work across a variety of platforms / rubies)

Gem Version	Release Date	libcurl versions
1.0.8	Feb 10, 2025	7.58 – 8.12.1
1.0.7	Feb 09, 2025	7.58 – 8.12.1
1.0.6	Aug 23, 2024	7.58 – 8.12.1
1.0.5	Jan 2023	7.58 – 8.12.1
1.0.4	Jan 2023	7.58 – 8.12.1
1.0.3*	Dec 2022	7.58 – 8.12.1
1.0.2*	Dec 2022	7.58 – 8.12.1
1.0.1	Apr 2022	7.58 – 8.12.1
1.0.0	Jan 2022	7.58 – 8.12.1
0.9.8	Jan 2019	7.58 – 7.81
0.9.7	Nov 2018	7.56 – 7.60
0.9.6	May 2018	7.51 – 7.59
0.9.5	May 2018	7.51 – 7.59
0.9.4	Aug 2017	7.41 – 7.58
0.9.3	Apr 2016	7.26 – 7.58

*avoid using these version are known to have issues with segmentation faults

Installation…

… will usually be as simple as:

$ gem install curb

On Windows, make sure you’re using the DevKit and
the development version of libcurl. Unzip, then run this in your command
line (alter paths to your curl location, but remember to use forward slashes):

gem install curb –platform=ruby – –with-curl-lib=C:/curl-7.39.0-devel-mingw32/lib –with-curl-include=C:/curl-7.39.0-devel-mingw32/include

Note that with Windows moving from one method of compiling to another as of Ruby 2.4 (DevKit -> MYSYS2),
the usage of Ruby 2.4+ with this gem on windows is unlikely to work. It is advised to use the
latest version of Ruby 2.3 available HERE

Or, if you downloaded the archive:

$ rake compile && rake install

If you have a weird setup, you might need extconf options. In this case, pass
them like so:

$ rake compile EXTCONF_OPTS=‘–with-curl-dir=/path/to/libcurl –prefix=/what/ever’ && rake install

Curb is tested only on GNU/Linux x86 and Mac OSX - YMMV on other platforms.
If you do use another platform and experience problems, or if you can
expand on the above instructions, please report the issue at http://github.com/taf2/curb/issues

On Ubuntu, the dependencies can be satisfied by installing the following packages:

18.04 and onwards

$ sudo apt-get install libcurl4 libcurl3-gnutls libcurl4-openssl-dev

< 18.04

$ sudo apt-get install libcurl3 libcurl3-gnutls libcurl4-openssl-dev

On RedHat:

$ sudo yum install ruby-devel libcurl-devel openssl-devel

Curb has fairly extensive RDoc comments in the source. You can build the
documentation with:

$ rake doc

Usage & examples

Curb provides two classes:

Curl::Easy - simple API, for day-to-day tasks.
Curl::Multi - more advanced API, for operating on multiple URLs simultaneously.

To use either, you will need to require the curb gem:

require 'curb'

Super simple API (less typing)

http = Curl.get("http://www.google.com/")
puts http.body

http = Curl.post("http://www.google.com/", {:foo =&gt; "bar"})
puts http.body

http = Curl.get("http://www.google.com/") do |http|
  http.headers['Cookie'] = 'foo=1;bar=2'
end
puts http.body

Simple fetch via HTTP:

c = Curl::Easy.perform("http://www.google.co.uk")
puts c.body

Same thing, more manual:

c = Curl::Easy.new("http://www.google.co.uk")
c.perform
puts c.body

Additional config:

http = Curl::Easy.perform("http://www.google.co.uk") do |curl|
  curl.headers["User-Agent"] = "myapp-0.0"
  curl.verbose = true
end

Same thing, more manual:

c = Curl::Easy.new("http://www.google.co.uk") do |curl|
  curl.headers["User-Agent"] = "myapp-0.0"
  curl.verbose = true
end

c.perform

HTTP basic authentication:

c = Curl::Easy.new("http://github.com/")
c.http_auth_types = :basic
c.username = 'foo'
c.password = 'bar'
c.perform

HTTP “insecure” SSL connections (like curl -k, –insecure) to avoid Curl::Err::SSLCACertificateError:

c = Curl::Easy.new("https://github.com/")
c.ssl_verify_peer = false
c.perform

Supplying custom handlers:

c = Curl::Easy.new("http://www.google.co.uk")

c.on_body { |data| print(data) }
c.on_header { |data| print(data) }

c.perform

Reusing Curls:

c = Curl::Easy.new

["http://www.google.co.uk", "http://www.ruby-lang.org/"].map do |url|
  c.url = url
  c.perform
  c.body
end

HTTP POST form:

Note: Instance methods like easy.http_post(...) do not accept a URL argument. Set the URL first (for example, Curl::Easy.new(url) or easy.url = url) and then call easy.http_post(...). If you want to pass the URL directly to the call, use the class/module helpers such as Curl::Easy.http_post(url, ...) or Curl.post(url, ...).

c = Curl::Easy.http_post("http://my.rails.box/thing/create",
                         Curl::PostField.content('thing[name]', 'box'),
                         Curl::PostField.content('thing[type]', 'storage'))

HTTP POST file upload:

c = Curl::Easy.new("http://my.rails.box/files/upload")
c.multipart_form_post = true
c.http_post(Curl::PostField.file('thing[file]', 'myfile.rb'))

### Custom request target

Some advanced scenarios need a request-target that differs from the URL host/path (for example, absolute-form targets or special values like `*`). If your libcurl supports `CURLOPT_REQUEST_TARGET` (libcurl ≥ 7.55), you can override it:

```ruby
c = Curl::Easy.new("http://127.0.0.1:9129/methods")
c.request_target = "http://localhost:9129/methods"  # absolute-form target
c.headers = { 'Host' =&gt; 'example.com' }              # override Host header if needed
c.perform

For HTTPS, prefer easy.resolve = ["host:443:IP"] to keep Host/SNI/certificates aligned.

### Using HTTP/2

```ruby
c = Curl::Easy.new("https://http2.akamai.com")
c.set(:HTTP_VERSION, Curl::HTTP_2_0)

c.perform
puts (c.body.include? "You are using HTTP/2 right now!") ? "HTTP/2" : "HTTP/1.x"

Multi Interface (Basic HTTP GET):

# make multiple GET requests
easy_options = {:follow_location =&gt; true}
# Use Curl::CURLPIPE_MULTIPLEX for HTTP/2 multiplexing
multi_options = {:pipeline =&gt; Curl::CURLPIPE_HTTP1}

Curl::Multi.get(['url1','url2','url3','url4','url5'], easy_options, multi_options) do|easy|
  # do something interesting with the easy response
  puts easy.last_effective_url
end

Multi Interface (Basic HTTP POST):

# make multiple POST requests
easy_options = {:follow_location =&gt; true, :multipart_form_post =&gt; true}
multi_options = {:pipeline =&gt; Curl::CURLPIPE_HTTP1}


url_fields = [
  { :url =&gt; 'url1', :post_fields =&gt; {'f1' =&gt; 'v1'} },
  { :url =&gt; 'url2', :post_fields =&gt; {'f1' =&gt; 'v1'} },
  { :url =&gt; 'url3', :post_fields =&gt; {'f1' =&gt; 'v1'} }
]

Curl::Multi.post(url_fields, easy_options, multi_options) do|easy|
  # do something interesting with the easy response
  puts easy.last_effective_url
end

Multi Interface (Advanced):

responses = {}
requests = ["http://www.google.co.uk/", "http://www.ruby-lang.org/"]
m = Curl::Multi.new
# add a few easy handles
requests.each do |url|
  responses[url] = ""
  c = Curl::Easy.new(url) do|curl|
    curl.follow_location = true
    curl.on_body{|data| responses[url] &lt;&lt; data; data.size }
    curl.on_success {|easy| puts "success, add more easy handles" }
  end
  m.add(c)
end

m.perform do
  puts "idling... can do some work here"
end

requests.each do|url|
  puts responses[url]
end

Easy Callbacks

on_success is called when the response code is 2xx
on_redirect is called when the response code is 3xx
on_missing is called when the response code is 4xx
on_failure is called when the response code is 5xx
on_complete is called in all cases.

Cookies

Manual cookies: Set the outgoing Cookie header via easy.cookies = "name=value; other=val". This only affects the request header and does not modify libcurl’s internal cookie engine.
Cookie engine: Enable with easy.enable_cookies = true. Optionally set easy.cookiefile (to load) and/or easy.cookiejar (to persist). Cookies received via Set-Cookie go into this engine.
Inspect engine cookies: easy.cookielist returns an array of strings (Netscape or Set-Cookie format).
Modify engine cookies: use easy.cookielist = ... or easy.set(:cookielist, ...) with either a Set-Cookie style string, Netscape cookie lines, or special commands: "ALL" (clear), "SESS" (remove session cookies), "FLUSH" (write to jar), "RELOAD" (reload from file).
Clearing manual cookies: assign an empty string (easy.cookies = ''). Assigning nil has no effect in current versions.

Examples:

easy = Curl::Easy.new("https://example.com")

# Use the cookie engine and persist cookies
easy.enable_cookies = true
easy.cookiejar = "/tmp/cookies.txt"
easy.perform

# Later: inspect and tweak engine cookies
p easy.cookielist
easy.cookielist = 'ALL' # clear stored cookies

# Send custom Cookie header for a single request
easy.cookies = "flag=1; session_override=abc"
easy.perform
easy.cookies = ''  # clear manual Cookie header

Modules

Classes