regexp help - substring of a backreference
in [Ruby]
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From: Bryan Kennerley on 7 Aug 2010 09:33 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/.
From: Benoit Daloze on 7 Aug 2010 10:02 On 7 August 2010 15:33, Bryan Kennerley <me(a)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>} } => "<a href=\"http://\u0001\" 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
From: Benoit Daloze on 7 Aug 2010 10:04 On 7 August 2010 16:02:31 UTC+2, Benoit Daloze <eregontp(a)gmail.com> wrote: > On 7 August 2010 15:33, Bryan Kennerley <me(a)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 Missed the first '\1' : text.gsub(/http:?\/*(\w+[\w\-\.\/~\?%&=#;,\+:\@]+)/) {|match| %Q{<a href="http://#{$1}" target="_blank">http://#{$1[0...50]}</a>} }
From: David A. Black on 7 Aug 2010 10:08 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
From: Bryan Kennerley on 7 Aug 2010 12:55 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 :) -- Posted via http://www.ruby-forum.com/.
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