Does Ruby have any built-in method for escaping and unescaping strings? In the past, I've used regular expressions; however, it occurs to me that Ruby probably does such conversions internally all the time. Perhaps this functionality is exposed somewhere.
So far I've come up with these functions. They work, but they seem a bit hacky:
def escape(s) s.inspect[1..-2] end def unescape(s) eval %Q{"#{s}"} end Is there a better way?
If you don't want to use eval, but are willing to use the YAML module, you can use it instead:
require 'yaml' def unescape(s) YAML.load(%Q(---\n"#{s}"\n)) end The advantage to YAML over eval is that it is presumably safer. cane disallows all usage of eval. I've seen recommendations to use $SAFE along with eval, but that is not available via JRuby currently.
For what it is worth, Python does have native support for unescaping backslashes.
There are a bunch of escaping methods, some of them:
# Regexp escapings >> Regexp.escape('\*?{}.') => \\\*\?\{\}\. >> URI.escape("test=100%") => "test=100%25" >> CGI.escape("test=100%") => "test%3D100%25" So, its really depends on the issue you need to solve. But I would avoid using inspect for escaping.
Update - there is a dump, inspect uses that, and it looks like it is what you need:
>> "\n\t".dump => "\"\\n\\t\"" Caleb function was the nearest thing to the reverse of String #inspect I was able to find, however it contained two bugs:
I fixed the above bugs and this is the updated version:
UNESCAPES = { 'a' => "\x07", 'b' => "\x08", 't' => "\x09", 'n' => "\x0a", 'v' => "\x0b", 'f' => "\x0c", 'r' => "\x0d", 'e' => "\x1b", "\\\\" => "\x5c", "\"" => "\x22", "'" => "\x27" } def unescape(str) # Escape all the things str.gsub(/\\(?:([#{UNESCAPES.keys.join}])|u([\da-fA-F]{4}))|\\0?x([\da-fA-F]{2})/) { if $1 if $1 == '\\' then '\\' else UNESCAPES[$1] end elsif $2 # escape \u0000 unicode ["#$2".hex].pack('U*') elsif $3 # escape \0xff or \xff [$3].pack('H2') end } end # To test it while true line = STDIN.gets puts unescape(line) end YAML's ::unescape doesn't seem to escape quote characters, e.g. ' and ". I'm guessing this is by design, but it makes me sad.
You definitely do not want to use eval on arbitrary or client-supplied data.
This is what I use. Handles everything I've seen and doesn't introduce any dependencies.
UNESCAPES = { 'a' => "\x07", 'b' => "\x08", 't' => "\x09", 'n' => "\x0a", 'v' => "\x0b", 'f' => "\x0c", 'r' => "\x0d", 'e' => "\x1b", "\\\\" => "\x5c", "\"" => "\x22", "'" => "\x27" } def unescape(str) # Escape all the things str.gsub(/\\(?:([#{UNESCAPES.keys.join}])|u([\da-fA-F]{4}))|\\0?x([\da-fA-F]{2})/) { if $1 if $1 == '\\' then '\\' else UNESCAPES[$1] end elsif $2 # escape \u0000 unicode ["#$2".hex].pack('U*') elsif $3 # escape \0xff or \xff [$3].pack('H2') end } end Ruby's inspect can help:
"a\nb".inspect => "\"a\\nb\"" Normally if we print a string with an embedded line-feed, we'd get:
puts "a\nb" a b If we print the inspected version:
puts "a\nb".inspect "a\nb" Assign the inspected version to a variable and you'll have the escaped version of the string.
To undo the escaping, eval the string:
puts eval("a\nb".inspect) a b I don't really like doing it this way. It's more of a curiosity than something I'd do in practice.
I suspect that Shellwords.escape will do what you're looking for
https://ruby-doc.org/stdlib-1.9.3/libdoc/shellwords/rdoc/Shellwords.html#method-c-shellescape