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

I have a uni assignment to complete by 1/26/2005 but am struggling with perl as I have had only 1 session. I am running activeperl on windows xp and I need to create a perl script that will print the last line of a text file with a ";" in the line. Also I need to create a batch file that will create a sorted frequency list from a text file but that will include "'"'s and "-"'s as parts of words but not dashes which are represented in the file as "---"? Please help if only to tell me where I could look to find out I can't really make much sense of the "perlre" documentation!

Retitled by davido.

Replies are listed 'Best First'.
Re: homework: Simple matching and sorting
by holli (Abbot) on Jan 24, 2005 at 20:31 UTC
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Re: homework: Simple matching and sorting
by CountZero (Bishop) on Jan 24, 2005 at 20:37 UTC
    For the first part of your assignment: 
    use strict;

my $lastline;

while (<DATA>) {
    $lastline = $_ if /;/;
}
print $lastline;

__DATA__
This is not the right line
This is OK, it contains a ;
This is no good either
Hey, a ; in this line!
Drop this.

    [download]
    Of course you will want to change the <DATA> filehandle for some proper filehandle pointing to the text file.

    CountZero

    "If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law

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[d/l]
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Re: homework: Simple matching and sorting
by CountZero (Bishop) on Jan 24, 2005 at 20:45 UTC
    Or even shorter: 
    use strict;

my @lines=grep(/;/, <DATA>);

print pop @lines;

__DATA__
This is not the right line
This OK, it contains a ;
This is no good either
Hey, a ; in this line!
Drop this.

    [download]
    It is shorter, but it uses more memory if the text file is large as it reads in all lines of the file and keeps all lines with a ';' only to print the last line.

    CountZero

    "If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law

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[d/l]
Re: homework: Simple matching and sorting
by Anonymous Monk on Jan 25, 2005 at 10:06 UTC
    1. perl -ne '$,=$_if/;/END{print$,}' file.txt 
    2. perl -ne '$,{$_}++for/(?:[\x27\w]+|-(?!--))+/g;
END{for(sort{$,{$a}<=>$,{$b}}keys(%,)){printf"%4d: %s\n",$,{$_},$_}}' 
+file.txt

      [download]
    I didn't test the first one, but I did test the second.
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Re: homework: Simple matching and sorting
by DrHyde (Prior) on Jan 25, 2005 at 10:25 UTC
    ++ for at least admitting that this is homework. Your honesty makes a refreshing change from certain other people here.
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Re: homework: Simple matching and sorting
by tphyahoo (Vicar) on Jan 25, 2005 at 10:45 UTC
    What's a sorted frequency list?
[reply]

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