Replace "&" to "\&" in Ruby Seems Impossible

Replace & to \& in Ruby seems impossible?

Your linked question provides a solution - use the block form of gsub:

irb(main):009:0> puts "asdf & asdf".gsub("&"){'\&'}
asdf \& asdf

How to replace & with \& with gsub on rails?

Use triple \ in the replacement string:

print 'Company & Co. KG'.gsub('&', '\\\&')
# Company \& Co. KG=> nil

You can check that a single backslash is added by checking the length of both strings:

'Company & Co. KG'.size
# => 16
'Company & Co. KG'.gsub('&', '\\\&').size
# => 17

To understand it better, read about escaping:

• https://en.wikibooks.org/wiki/Ruby_Programming/Strings#Single_quotes
• https://gist.github.com/kbaribeau/1103102
• Weird backslash substitution in Ruby

EDIT:

\& is a backreference to the whole match (like \0)

'Company & Co. KG'.gsub(/Co/, '-\&-')
# => "-Co-mpany & -Co-. KG"
'Company & Co. KG'.gsub(/Co/, '-\0-')
# => "-Co-mpany & -Co-. KG"

How to replace single quote to backslash in ruby?

Ruby is interpreting the \' as a backreference to the post-match string($'). So, you are replacing the quote with everything after the quote:

<space>DROP TABLE Suppliers
     V
"105;' DROP TABLE Suppliers"

Here it is with a backreference to the pre-match variable($`):

string = "105;' DROP TABLE Suppliers"
new_string = string.gsub("'", %q(\`))
p new_string

--output:--
"105;105; DROP TABLE Suppliers"

I can't find any documentation for backreferences to ruby's global variables, so congratulations you are a ruby pioneer.

impossible to replace the character with gsub

Replace your code with this:

def replace_chars(name)
  chars = {
      "̤" => "ç",
      "Ì©" => "é",
      "•"  => "ï",
      "â„¢"  => "ô",
      "Ž"   => 'é',
      "‘"  => "ë",
      "Â"    => "ç"          
    }
  puts "before #{name}"
  chars.each do |key,value|
    name.gsub!(key,value)
  end
  puts "after #{name}"
end

replace_chars('̤liver Žponime')
before ̤liver Žponime
after çliver éponime

`string.replace` doesn’t change the variable

According to the Javascript standard, String.replace isn't supposed to modify the string itself. It just returns the modified string. You can refer to the Mozilla Developer Network documentation for more info.

You can always just set the string to the modified value:

variableABC = variableABC.replace('B', 'D')

Edit: The code given above is to only replace the first occurrence.

To replace all occurrences, you could do:

 variableABC = variableABC.replace(/B/g, "D");  

To replace all occurrences and ignore casing

 variableABC = variableABC.replace(/B/gi, "D");  

How can I replace new lines with \n character

> s = "hi\nthere"
> puts s
hi
there
> puts s.gsub(/\n/, "\\n")
hi\nthere

Ruby Regex Replace Last Occurence of Grouping

If I correctly understood, you are interested in gsub with codeblock:

str.gsub(PATTERN) { |mtch|
  puts mtch                # the whole match
  puts $~[3]               # the third group
  mtch.gsub($~[3], 'NEW')  # the result
}

'abc'.gsub(/(b)(c)/) { |m| m.gsub($~[2], 'd') }
#⇒ "abd"

Probably you should handle the case when there are no 40-s occureneces at all, like:

gsub($~[1], "NEW$~[1]") if $~[3].nil?

To handle all the possible cases, one might declare the group for Foo:

#                           NOTE THE GROUP ⇓⇓⇓⇓⇓
▶ re = /(([1-3,5-9][0-9]|([4][0-9]))[a-z])*(Foo)/
#⇒ /(([1-3,5-9][0-9]|([4][0-9]))[a-z])*(Foo)/
▶ inp.gsub(re) do |mtch|
▷   $~[3].nil? ? mtch.gsub($~[4], "NEW#{$~[4]}") : mtch.gsub(/#{$~[3]}/, 'NEW')  
▷ end
#⇒ "12a23b34cNEWd56eFoo\n12a45b34cNEWd89eFoo\nNEWaFoo\nNEWFoo\n12a23bNEWFoo"

Hope it helps.

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