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Asked: 2026-06-14T06:02:05+00:00

I read the documentation of url_encode . Is there a table that tells me

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I read the documentation of url_encode.

Is there a table that tells me exactly which character is encoded to what, using url_encode?

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  1. Editorial Team

    ERB’s url_encode can be tweaked:

    def url_encode(s)
  s.to_s.dup.force_encoding("ASCII-8BIT").gsub(%r[^a-zA-Z0-9_\-.]/) {
    sprintf("%%%02X", $&.unpack("C")[0])
  }
end

    to:

    def url_encode(s, regex=%r[^a-zA-Z0-9_\-.]/)
  s.to_s.dup.force_encoding("ASCII-8BIT").gsub(regex) {
    sprintf("%%%02X", $&.unpack("C")[0])
  }
end

url_encode('pop', /./)
=> "%70%6F%70"

    In addition, Ruby’s CGI and URI modules have the ability to encode URLs, converting restricted characters to entities, so don’t overlook their offerings.

    For instance, escaping characters for URL parameters:

    CGI.escape('http://www.example.com')
=> "http%3A%2F%2Fwww.example.com"

CGI.escape('<body><p>foo</p></body>')
=> "%3Cbody%3E%3Cp%3Efoo%3C%2Fp%3E%3C%2Fbody%3E"

    Ruby CGI’s escape also uses a small regex to figure out which characters should be escaped in a URL. This is the method’s definition from the documentation:

    def CGI::escape(string)
  string.gsub(%r([^ a-zA-Z0-9_.-]+)/) do
    '%' + $1.unpack('H2' * $1.bytesize).join('%').upcase
  end.tr(' ', '+')
end

    You also override that and change the regex, or expose it for your own use inside your redefinition of the method:

    def CGI::escape(string, escape_regex=%r([^ a-zA-Z0-9_.-]+)/)
  string.gsub(escape_regex) do
    '%' + $1.unpack('H2' * $1.bytesize).join('%').upcase
  end.tr(' ', '+')
end

    URI.encode_www_form_component also does a similar encoding, the only differences in characters are * and :

    URI.encode_www_form_component('<p>foo</p>')
=> "%3Cp%3Efoo%3C%2Fp%3E"

    And, similarly to overriding CGI::escape, you can override the regex in URI.encode_www_form_component:

    def self.encode_www_form_component(str, regex=%r[^*\-.0-9A-Z_a-z]/)
  str = str.to_s
  if HTML5ASCIIINCOMPAT.include?(str.encoding)
    str = str.encode(Encoding::UTF_8)
  else
    str = str.dup
  end
  str.force_encoding(Encoding::ASCII_8BIT)
  str.gsub!(regex, TBLENCWWWCOMP_)
  str.force_encoding(Encoding::US_ASCII)
end
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