Regexp help - substring of a backreference

ruby-talk
1

I'm putting together a web forum and want to parse web addresses that
are part of messages into clickable links. This is my attempt, I'm not
claiming its perfect but it works:

text.gsub!(/http:?\/*(\w+[\w\-\.\/~\?%&=#;,\+:\@]+)/,
          ' <a href="http://\1" target="_blank">http://\1</a>')

The problem is that some web addresses are incredibly long, so I want
the link text to be limited to, say, 50 chars. i.e. the second \1 needs
to be \1[0..49] or something. I can't figure out any easy way of doing
it, any ideas?

···

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Posted via http://www.ruby-forum.com/.

2

$ ri gsub!

Implementation from String

···

On 7 August 2010 15:33, Bryan Kennerley <me@bryankennerley.co.uk> wrote:

I'm putting together a web forum and want to parse web addresses that
are part of messages into clickable links. This is my attempt, I'm not
claiming its perfect but it works:

text.gsub!(/http:?\/*(\w+[\w\-\.\/~\?%&=#;,\+:\@]+)/,
' <a href="http://\1" target="_blank">http://\1</a>')

The problem is that some web addresses are incredibly long, so I want
the link text to be limited to, say, 50 chars. i.e. the second \1 needs
to be \1[0..49] or something. I can't figure out any easy way of doing
it, any ideas?
--
Posted via http://www.ruby-forum.com/\.

------------------------------------------------------------------------------
  str.gsub!(pattern, replacement) -> str or nil
  str.gsub!(pattern) {|match| block } -> str or nil
  str.gsub!(pattern) -> an_enumerator

------------------------------------------------------------------------------

Performs the substitutions of String#gsub in place, returning
str, or nil if no substitutions were performed. If no block and
no replacement is given, an enumerator is returned instead.
--

text.gsub(/http:?\/*(\w+[\w\-\.\/~\?%&=#;,\+:\@]+)/) { %Q{<a
href="http://\1" target="_blank">http://#{$1[0…50]}</a>} }
=> "<a href=\"http://\u0001&quot;
target=\"_blank\">http://mydgfsjceeeefknuxqbkqkhdslkjdhxfilunhefilxqhleiufn</a>"

I am using %Q{str}, as "str" because you already have quotes. You
should also use %r{regex} for you Regexp, as it contains '/'.

Benoit Daloze

3

Hi --

···

On Sat, 7 Aug 2010, Bryan Kennerley wrote:

I'm putting together a web forum and want to parse web addresses that
are part of messages into clickable links. This is my attempt, I'm not
claiming its perfect but it works:

text.gsub!(/http:?\/*(\w+[\w\-\.\/~\?%&=#;,\+:\@]+)/,
         ' <a href="http://\1" target="_blank">http://\1</a>')

The problem is that some web addresses are incredibly long, so I want
the link text to be limited to, say, 50 chars. i.e. the second \1 needs
to be \1[0..49] or something. I can't figure out any easy way of doing
it, any ideas?

You can use the block form, plus the thread-local $ variables:

   text = "a bunch of miscellaneous words"
   text.gsub!(/a b(.+)/) { $1[0,10] }
   puts text # unch of mi

David

--
David A. Black, Senior Developer, Cyrus Innovation Inc.

   The Ruby training with Black/Brown/McAnally
   Compleat Philadelphia, PA, October 1-2, 2010
   Rubyist http://www.compleatrubyist.com

4

Missed the first '\1' :
text.gsub(/http:?\/*(\w+[\w\-\.\/~\?%&=#;,\+:\@]+)/) {|match| %Q{<a
href="http://#{$1}" target="_blank">http://#{$1[0…50]}</a>} }

···

On 7 August 2010 16:02:31 UTC+2, Benoit Daloze <eregontp@gmail.com> wrote:

On 7 August 2010 15:33, Bryan Kennerley <me@bryankennerley.co.uk> wrote:

I'm putting together a web forum and want to parse web addresses that
are part of messages into clickable links. This is my attempt, I'm not
claiming its perfect but it works:

text.gsub!(/http:?\/*(\w+[\w\-\.\/~\?%&=#;,\+:\@]+)/,
' <a href="http://\1" target="_blank">http://\1</a>')

The problem is that some web addresses are incredibly long, so I want
the link text to be limited to, say, 50 chars. i.e. the second \1 needs
to be \1[0..49] or something. I can't figure out any easy way of doing
it, any ideas?
--
Posted via http://www.ruby-forum.com/\.

$ ri gsub!

Implementation from String
------------------------------------------------------------------------------
str.gsub!(pattern, replacement) -> str or nil
str.gsub!(pattern) {|match| block } -> str or nil
str.gsub!(pattern) -> an_enumerator

------------------------------------------------------------------------------

Performs the substitutions of String#gsub in place, returning
str, or nil if no substitutions were performed. If no block and
no replacement is given, an enumerator is returned instead.
--

text.gsub(/http:?\/*(\w+[\w\-\.\/~\?%&=#;,\+:\@]+)/) { %Q{<a href="http://\1" target="_blank">http://#{$1[0…50]}</a>} }

I am using %Q{str}, as "str" because you already have quotes. You should also use %r{regex} for you Regexp, as it contains '/'.

Benoit Daloze

5

Benoit Daloze wrote:

text.gsub(/http:?\/*(\w+[\w\-\.\/~\?%&=#;,\+:\@]+)/) {|match| %Q{<a
href="http://#{$1}" target="_blank">http://#{$1[0…50]}</a>} }

Thanks, works a charm :slight_smile:

···

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