From: "Peter Schüller" <peter.schueller@...>
Date: 2002-10-01T21:12:43+09:00
Subject: Re: regex problem

Thank you for your help !

This way i was able to adapt my sql.rb file of the ruby DBI database
interface.

I think my addition (the gsub(/\\/,'\&\&')) is needed for escaping
ruby-strings really reliable.
Currently i do a web-analysis with ruby and postgresql and had many
postgresql Errors because of Referrers ending with "\"


    ## Quote strings appropriately for SQL statements
    def quote(value)
      case value
      when String
>  value = value.gsub(/\\/,'\&\&').gsub(/'/, "''") # ' (for ruby-mode)
  "'#{value}'"
      when NilClass
  "NULL"
      when TrueClass
        "'t'"
      when FalseClass
        "'f'"
      when Array
  value.collect { |v| quote(v) }.join(", ")
      when DBI::Date, DBI::Time, DBI::Timestamp, ::Date, ::Time
        "'#{value.to_s}'"
      else
  value.to_s
      end
    end

Did i miss another possibility to quote my SQL correctly or was this part
really missing in the DBI ?

Peter Schueller


----- Original Message -----
From: "ts" <decoux@moulon.inra.fr>
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>
Cc: <ruby-talk@ruby-lang.org>
Sent: Tuesday, October 01, 2002 1:36 PM
Subject: Re: regex problem


> >>>>> "P" == =?iso-8859-1?Q?Peter Sch=FCller?= <iso-8859-1> writes:
>
> P> i want to substitute one \ with two \\
>
>  It's in the faq, see
>
>    http://www.rubycentral.com/faq/rubyfaq-9.html#ss9.18
>
> Regexp.quote('\\') escapes a backslash.
>
> It gets trickier if you're using sub and gsub, Say you write gsub(/\\/,
> '\\\\'), hoping to replace each backslash with two. The second argument is
> converted to '\\' in syntax analysis. When the substitution occurs, the
> regular expression engine converts this to '\', so the net effect is to
> replace each single backslash with another single backslash. You need to
> write gsub(/\\/, '\\\\\\')!
>
> However, using the fact that \& contains the matched string, you could
also
> write gsub(/\\/, '\&\&').
>
> If you use the block form of gsub, i.e. gsub(/\\/){'\\\\'}, the string for
> substitution is analyzed only once (during the syntax pass) and the result
> is what you intended.
>
>
>
> Guy Decoux
>
>