# RegExp & File read help

**URL:** <https://www.ruby-forum.com/t/regexp-file-read-help/107922>\
**Category:** Ruby\
**Created:** [June 27, 2007, 2:53pm UTC](https://www.ruby-forum.com/t/regexp-file-read-help/107922 "2007-06-27T14:53:59Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Don\_L](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@Don\_L](https://www.ruby-forum.com/u/Don_L)\
**Post date:** [June 27, 2007, 2:53pm UTC](https://www.ruby-forum.com/t/regexp-file-read-help/107922/1 "2007-06-27T14:53:59Z")

</div>

Hi All,

I am trying to parse out a list of elements from a set of xml file  
which match a given regular expression. I am sure there is probably a  
way to do this using an xml parsing library, but I thought it might  
be just as easy to do so with regular expressions.

My thought was to do the following:

Iterate through a set of files in a directory.  
Search each file for a set of lines which match a given regular  
expression.  
Add the capture group in each match to an array.  
Sort the array and remove any duplicate values  
print the results.

Here are the steps I have tried in building my script:

First, I tested to make sure my regular expression actually matched  
against the pattern I was seeking. This seemed to work as expected.

* * *

regexp = Regexp.new(/\<Font-family codeSet="\w\*" fontId="\d\*"\>(\w\*)  
\</Font-family\>/m)  
string = %q(Helvetica\</Font-  
family\>)  
if string =~ regexp  
puts “yes, there is a match. #{$1}”  
end

* * *

Returns \>\> yes, there is a match. Helvetica

Then, I tested a different method which would add the matches to an  
array. This also seemed to work as expected.

* * *

regexp = Regexp.new(/\<Font-family codeSet="\w\*" fontId="\d\*"\>(\w\*)  
\</Font-family\>/m)  
string = %q(Helvetica\</Font-  
family\>)

a = regexp.match(string)  
puts a[1]

* * *

Returns \>\> Helvitica

Next, I tested opening a file and returning all lines. This seemed to  
work as well.

* * *

file = File.new(’/Users/donlevan/Desktop/DDRs/Apple Dealer Price  
List.xml’)

file.each do |line|  
puts line  
end

* * *

Returns \>\> \<?xml version="1.0" encoding="UTF-16"?\>  
  
  
  
  
 … end of file

Where I am getting stuck is in the next code fragment, in which I am  
testing each line to see if there is a match. There should be as the  
string I used above for testing was pulled directly from one line of  
the file. Unfortunately, I get an error and no -matches.

* * *

regexp = Regexp.new(/\<Font-family codeSet="\w\*" fontId="\d\*"\>(\w\*)  
\</Font-family\>/m)  
file = File.new(’/Users/donlevan/Desktop/DDRs/Apple Dealer Price  
List.xml’)

file.each do |string|  
if string =~ regexp  
puts “yes, there is a match. #{$1}”  
end  
end

* * *

Returns \>\>

RubyMate r6354 running Ruby r1.8.6 (/usr/local/bin/ruby)

> > > untitled

/Users/donlevan/Library/Application Support/TextMate/Support/lib/  
scriptmate.rb:29: warning: Insecure world writable dir /Users/  
donlevan/Library/Application Support in PATH, mode 040706  
Program exited.

I would be grateful for any assistance. Thanks so much.

Don L.  
Brooklyn, New York

---

<div class="post-metadata">

**Author:** ![Don\_L](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@Don\_L](https://www.ruby-forum.com/u/Don_L)\
**Post date:** [June 27, 2007, 4:52pm UTC](https://www.ruby-forum.com/t/regexp-file-read-help/107922/2 "2007-06-27T16:52:13Z")

</div>

Hi Don,

> I am sure there is probably a  
> way to do this using an xml parsing library, but I thought it might  
> be just as easy to do so with regular expressions.

Hpricot is a good choice.

> Where I am getting stuck is in the next code fragment, in which I am  
> testing each line to see if there is a match. There should be as the  
> string I used above for testing was pulled directly from one line of  
> the file. Unfortunately, I get an error and no -matches.
> 
> * * *
> 
> regexp = Regexp.new(/\<Font-family codeSet="\w\*" fontId="\d\*"\>(\w\*)

In the regexp, you need to escape the minus sign also, otherwise,  
it is interpreted as a range of signs, i.e. f-t =[‘f’,‘g’,…,‘t’]

> regexp = Regexp.new(/\<Font-family codeSet="\w\*" fontId="\d\*"\>(\w\*)  
> \</Font-family\>/m)

Best regards,

Axel

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<div class="post-metadata">

**Author:** ![Don\_L](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@Don\_L](https://www.ruby-forum.com/u/Don_L)\
**Post date:** [June 27, 2007, 5:31pm UTC](https://www.ruby-forum.com/t/regexp-file-read-help/107922/3 "2007-06-27T17:31:20Z")

</div>

Hi –

On Wed, 27 Jun 2007, Axel E. wrote:

> > string I used above for testing was pulled directly from one line of  
> > the file. Unfortunately, I get an error and no -matches.
> > 
> > * * *
> > 
> > regexp = Regexp.new(/\<Font-family codeSet="\w\*" fontId="\d\*"\>(\w\*)
> 
> In the regexp, you need to escape the minus sign also, otherwise,  
> it is interpreted as a range of signs, i.e. f-t =[‘f’,‘g’,…,‘t’]

Only inside a character class. Otherwise it’s just a minus sign:

irb(main):017:0\> Regexp.new(/a-z/).match(“a”)  
=\> nil  
irb(main):018:0\> Regexp.new(/a-z/).match(“literal a-z”)  
=\> #MatchData:0x312ce8

David

---

<div class="post-metadata">

**Author:** ![Don\_L](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@Don\_L](https://www.ruby-forum.com/u/Don_L)\
**Post date:** [June 27, 2007, 6:44pm UTC](https://www.ruby-forum.com/t/regexp-file-read-help/107922/4 "2007-06-27T18:44:28Z")

</div>

Hi David and Alex,

Thanks for your help. I don’t have it solved yet, but you both have  
cleared up the confusion.

Thanks,

Don