in reply to regular expressions

I think you want the regex I show in this little program. It starts with an "a", has one of more non-newline characters, then uses the alternation (f|g) to denote that the whole thing can end with either of those characters. 

#!/usr/bin/perl

while( <DATA> )
    {
    chomp;
    print "$_ matches!\n" if /^a.+(f|g)$/;
    }
    
__DATA__
axxxi
bxg
cxxf
axxxh
axxxg
axxxf

[download]
--
brian d foy <bdfoy@cpan.org>

Replies are listed 'Best First'.
Re^2: regular expressions
by reasonablekeith (Deacon) on Mar 01, 2005 at 08:50 UTC
    Slightly picky, but I'd use a character class to match the f or g. I'm pretty certain it'd be quicker, as perl isn't jumping through hoops to catch $1. 
    print "$_ matches!\n" if /^a.+[fg]$/;

    [download]
[reply]
[d/l]
Re^2: regular expressions
by wannabeboy (Novice) on Mar 01, 2005 at 08:56 UTC
    Hi it's me again, this is really what I'm trying to do, get each line of a file end if the word on the line begins with a has 1 or more words then ends with f or g (images files like amm.gif or ammre.jpg) get the word into a table @amourss. 
    #!usr/bin/perl
# 2005-03-01 :

# ouvrir le fichier contenant la liste des cartes
open(CARTES, "imagescartes.txt") or die "Ouverture du ficher imagescar
+tes.txt impossible: $!\n";
-T "imagescartes.txt" or print "ceci n'est pas un fichier texte\n";

while ($ligne = <CARTES>) 
{
    chop($ligne);
    while ($amourss .= /^a.+(f|g)$/g ) 
    {
        $total++;
    }
}

    [download]
[reply]
[d/l]

      If you are looking for particular filenames, I would expand the regular expression. I'd specify the file extension as much as possible, including the literal full stop that separates the name and extension. The /i flag is sometimes a good idea since some things like to make everything upper case. 

      /^a.*\.(jpg|gif)$/i

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      --
      brian d foy <bdfoy@cpan.org>
[reply]
[d/l]

      I think this will do what you want. 

      #!/usr/bin/perl
# 2005-03-01:
# Please always use strict and warnings, they will capture
# many common mistakes and typos
use strict;
use warnings;

# we may as well test it before we try to open it
unless (-T 'imagescartes.txt') {
     print "ceci n'est pas un fichier texte\n";
     exit 1;
}

# ouvrir le fichier contenant la liste des cartes
open CARTES, '<', 'imagescartes.txt' or die 'Ouverture du ficher image
+scartes.txt impossible: $!\n';

# this is the array where we store the image file names
my @amourss;
while (my $ligne = <CARTES>)
{
    chomp $ligne ;
    if ($ligne =~ /^a\S+\.(?:gif|jpg)$/) # will match exactly one word
                                         # begining a and ending in .g
+if or .jpg
                                         # the \S+ is one or more non 
+space chrs
                                         # a.gif not allowed use \S* t
+o allow it
    {
        push @amourss, $ligne;
    }
}

close CARTES;

print "found ", scalar @amourss, " images: ";
print join ", ", @amourss;
print "\n";
__END__

# input file used 
test.gif
this asilly.gif
abc.jpg
abcd.gif
absolutely not a.jpg

# results of running 
>./amourss
found 2 images: abc.jpg, abcd.gif
>

      [download]

      Update

      as Jasper points out a space is valid in filenames in most OSes so please feel free to change the regex to /^a.+\.(?:gif|jpg)$/ if you wish to allow spaces in filenames or /^a.*\.(?:gif|jpg)$/ if you wish to allow a.gif and a.jpg

      Cheers,
      R.

      Pereant, qui ante nos nostra dixerunt!
[reply]
[d/l]
[select]
        I don't think this is particularly good, because "this asilly.gif" and "absolutely not a.jpg", even though you've given them stupid names, are valid filenames.
[reply]

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