[wellylug] Perl regular expression problem with literal $

[Cliff Pratt]

Peter Davenport wrote:
> 
> 
>     Date: Sun, 01 Jun 2008 12:51:35 +1200
>     From: Cliff Pratt <enkidu at cliffp.com <mailto:enkidu at cliffp.com>>
>     Subject: Re: [wellylug] Perl regular expression problem with literal $
>     To: Wellington Linux Users Group <wellylug at lists.wellylug.org.nz
>     <mailto:wellylug at lists.wellylug.org.nz>>
>     Message-ID: <4841F297.7070409 at cliffp.com
>     <mailto:4841F297.7070409 at cliffp.com>>
>     Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
>      >Peter Davenport wrote:
>      >> Not a direct Linux issue, but I do run this process under Linux.
>      >>
>      >> I have a perl script to process some data with many records of
>     the form -
>      >> 'User xxxxxx transfered 123456kb of file yyyyyy at cost of
>     $1,234.56 to
>      >> machine zzzzz'
>      >>
>      >> This example is a bit made up but it illustrates the point. I am
>     trying
>      >> to extract the numbers for the kb and $.
>      >>
>      >> My perl RE to get the kb is m/ (\d+)kb / and this works as it
>     gets the
>      >> leading/trailing blanks and the numeric kb item into $1 variable.
>      >> However, for the money item, I tried m/ $([\d,.]+) / but the $
>     gets used
>      >> to indicate the end of record. Escaping it with backslash dosn't
>     work
>      >> either as it then seems to get interpreted as the start of a
>      >> scalar variable. How do I specify a literal $ in the RE?
>      >>
>      >> This data extraction requirement must be a common one and been
>     solved
>      >> before. I have not been able to locate a solution.
>      >> Can anyone help to resolve this please.
>      >>
> 
>      >
> 
>  
> 
>      >It's not matching your RE. The RE should read:
>      >/ \$([\d.]+ )/
>      >
>      >Note, no comma.
>      >
>      >Here's my test snippet:
>      >
>      >#!/usr/bin/perl
>      >
>      >use strict ;
>      >use warnings ;
>      >
>      >my $str = 'abcdef $1234.00 xyz' ;
>      >print "$str\n" ;
>      >$str =~ / \$([\d.]+ )/ ;
>      >print "$1\n" ;
>      >
> 
>     Thank you for this response. The escape of the $ character was part
>     of the answer that I needed, but that did not fix it completely. The
>     example code worked so I knew what to persevere with that. I had a
>     prior match statement with a 'g' option for global and that seemed
>     to swallow up the whole record and thus not match the bit I wanted
>     to extract on the later statement. Removing the 'g' from the prior
>     statement fixed it. I had not expected such interaction between
>     statements.
> 
That's interesting. Care to share a bit more of the code? I was thinking 
that the comma was the problem, but I see now that it wasn't. I don't 
know why I thought that now!!

It is useful to know that a bit of code works, isn't it?

Cheers,

Cliff