How to remove the new line characters from a string?

What's wrong with this?

String.strip only supports removing one character. That error is thrown as Elixir tries to convert "\r\n" to a single character (source):

iex(1)> s = "\r\n"
"\r\n"
iex(2)> <<s::utf8>>
** (ArgumentError) argument error

Moreover, String.strip has been deprecated in favor of String.trim, which does support a string as the second argument, but that function will only remove the exact sequence \r\n from the starting and ending of the string:

iex(1)> aaa = """
...(1)> fdsfds fdsfds
...(1)>   fdsfdsfds
...(1)> fdsfdsfds
...(1)> """
"fdsfds fdsfds\n  fdsfdsfds\nfdsfdsfds\n"
iex(2)> String.trim(aaa, "\r\n")
"fdsfds fdsfds\n  fdsfdsfds\nfdsfdsfds\n"
iex(3)> String.trim(aaa, "\r\n") == aaa
true

which I doubt is what you want as you said "I want to remove all the symbol of a new line". To remove all \r and \n, you can use String.replace twice:

iex(4)> aaa |> String.replace("\r", "") |> String.replace("\n", "")
"fdsfds fdsfds  fdsfdsfdsfdsfdsfds"