> On Jun 6, 2:15 pm, vorticitywo@gmail.com wrote:

> > Hello,

> > I have looked all over trying to find an example of how to grab
> > certain parts of a text file while ignoring others in the same line.

> > the file:

> > *************test.txt*************************
> > CREATED AT: Wed-June6-17:50 2007
> > NUM OBS: 1440
> > Values of two numbers:30.0/45.0 More text
> > that can be disregarded.
> > ***********************************************

> > Here is what I want to grab from it:

> > **************output************************
> > CREATED AT: Wed-June6-17:50 2007
> > VALUE: 30.0/45.0
> > **********************************************

> > Of course, the file is much larger than this, but I just want the
> > general syntax of how to accomplish this.

> > I've just started to use reg ex's, so bear with me...here is what I
> > have thusfar:

> > while(<file>){
> > if ($_=~ /(\d+)/)
> > {
> > print $_;

> > }
> > }

> A regular expression has two intentions.  First, it determines whether
> or not a given string of text "matches" some pattern.  Second, it is
> used to "pull" certain parts of that match out to be stored
> elsewhere.  You are only using the first intent - you're determining
> whether or not the line matches one or more digits.

> What you should instead do is find out if this text matches the actual
> format of the line, and secondarily pull out from that match the data
> you want to keep:

> #!/usr/bin/perl
> use strict;
> use warnings;

> while (my $line = <DATA>) {
>    if ($line =~ /^CREATED AT:/) {
>       #If line starts with that text, print the entire line
>       print $line;
>    }
>    if ($line =~ /^Values of.*?(\d+\.\d+\/\d+\.\d+)/) {
>       #If line starts with Values of, pull out
>       #the relevant text that you want to print
>       print "VALUE: $1\n";
>    }}

> __DATA__
> CREATED AT: Wed-June6-17:50 2007
> NUM OBS: 1440
> Values of two numbers:30.0/45.0 More text
> that can be disregarded.

> The above program outputs:
> CREATED AT: Wed-June6-17:50 2007
> VALUE: 30.0/45.0

> For more information on using meta characters and quantifiers (ie,
> the .*? above) and the captured submatches (the $1), please have a
> read of:
> perldoc perlretut
> perldoc perlre
> perldoc perlreref

> Paul Lalli