Regex grouping without storing

gmoque has asked for the wisdom of the Perl Monks concerning the following question:

Mongers,

I want to take data from two different inputs and then I want to apply a common regex to extract hex digits from it; the problem is that one device spits the hex values as 0x and the other data doesn't use the 0x, which makes my regex looks a bit ugly

My idea is to have something like this:

# Both connections are telnet based
sub getDataFromDevice {
# login to the device
# define the read/write commands
     &dumpData($conn, \%cmds)
}
sub getDataFromJtag {
# login to the device
# define the read/write commands
    &dumpData($conn, \%cmds)
}

sub dumpData {
    my $conn = shift;
    my $cmds = shift;

    my $addr = qr/^\s*0?x?[[:xdigit:]]{8}:\s+0?x?([[:xdigit:]]{8}).*$/
+;

    @output = $conn->cmd("$cmd->{read} 0xfeedbeef");
    push @obuf, (grep {s/$addr/$1/} @out);


}
[download]

This is what the two different commands output looks like

% read 0xfeedbeef

f80e205c: 30000000  ........
805306368
[download]

ppc8641-A[0,h] % mr 0xfeedbeef
0xf80e2044: 0x00100000   ........
[download]

The main issue I have is the 0?x? format in the $addr scalar looks horrible, so I was thinking to use grouping like (0x)? but the problem is this will break the substitution so I am wondering if there another way to write (0x)? without storing the data in $1

Thanks for your wisdom

Comment on Regex grouping without storing Select or Download Code

Replies are listed 'Best First'.
Re: Regex grouping without storing by davido (Cardinal) on Oct 06, 2011 at 17:54 UTC
`m/(?:` [download] The POD perlretut in the section called, "Non-capturing groupings" For sure it's covered in Learning Perl, perlre, perlretut, the Perl Cookbook, and Mastering Regular Expressions. Also by using Google with the search term, "Non-capturing regular expression grouping", the second result on the page is http://www.regular-expressions.info/refadv.html. There's no better source on Perl's regular expressions (as well as many other flavors) than Mastering Regular Expressions, by Jeffery Friedl (O'Reilly). Perl's POD may document the very latest changes, and it is comprehensive. But spending some time with the Owls book is quite an experience. `)/x` [download] Dave	[reply] [d/l] [select]
Re: Regex grouping without storing by AnomalousMonk (Archbishop) on Oct 06, 2011 at 17:31 UTC
See `(?:pattern)` in Extended Patterns section (third one in) in perlre.	[reply] [d/l]
Re: Regex grouping without storing by AR (Friar) on Oct 06, 2011 at 17:31 UTC
`(?:0x)?`	[reply] [d/l]


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