N0obieMonk has asked for the wisdom of the Perl Monks concerning the following question:

I am sorry for this stupid question respectable monks but I am new to perl programming and really need help with some perl code and explanations

I need some help on how to read a file, file example:

file1:"?!?!?!/pack/something/whatever.cacshdska"

I want my program to search for the word "something" and read everything except "!?!/pack/something/whatever.c" so if I print it it will output "?!?acshdska",so after it finds the word "something" it will ignore everything from it until ".c" and before it 3 characters before the first special character was found"!"

"

P.S. I am trying to convert the equivalent of every character in the file from to hex code but I don't need all the values from the file converted

{
    my $input = do {
        open my $in, '<', $ARGV[1];
        local $/;
        <$in>
    };    
    open my $out, '>', 'hex2.txt';  
     print $out unpack 'H*', $input;
   
}

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I was thinking of a split like this but I don't even know how to implement it, I'm just at the theory right now

split qr{\d\d\d(?:/\w+)+/\w+\.c}

Replies are listed 'Best First'.
Re: special pattern reading
by choroba (Cardinal) on Jan 13, 2016 at 09:51 UTC
    You can use a regular expression match. 
    #!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

my $string = '?!?!?!/pack/something/whatever.cacshdska';

my ($before, $after) = $string =~ /(...)\W.*something.*\.c(.*)/;
say for $before, $after;

    [download]

    • \W stands for a "non-word" character, it matches ! and ? among other characters.
    • a dot matches any character except a newline.
    • * means "the previous thing repeated zero or more times"
    • parentheses create "capture groups", what matches their contents gets returned (in this case, there are 2 capture groups, and we assing them to $before and $after). 
    ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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      your version reads the first "3" characters and everything after ".c" I need to read everything until the 3rd special character before the "/"

      #!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

my $string = '!2!ab!!!!/pack/something/whatever.cacshdska';

my ($before, $after) = $string =~ /(...)\W.*something.*\.c(.*)/;
say for $before, $after;

      [download]

      Output is "!2!acshdska" while I need output to be "!2!ab!acshdska" sorry if I wasn't clear enough ...my bad.

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[d/l]
        OK, I think I understand now. Or don't I? 
        #!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

for my $string ( '?!?!?!/pack/something/whatever.cacshdska',
                 '!2!ab!!!!/pack/something/whatever.cacshdska',
               ) {
    my ($before, $after) = $string =~ m{(.*)..\W/.*\.c(.*)};
    say "$before | $after";
}

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        ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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Re: special pattern reading
by hippo (Archbishop) on Jan 13, 2016 at 09:51 UTC

    If I understand you correctly then this substitution should be all you need for manipulating the filename:

    use strict;
use warnings;

my $file = '?!?!?!/pack/something/whatever.cacshdska';
$file =~ s/..![^!]*something.*\.c//;
print $file . "\n";

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[reply]
[d/l]

      Why is my version not working?

      use strict;
use warnings;
{
    my $input = do {
        open my $in, '<', '1.txt';
        local $/;
        <$in>
    };
until ( eof $in){

    my $file = <$in>;
    $file =~ s/..![^!]*something.*\.c//;
    print $file . "\n";
}

      [download]
[reply]
[d/l]

        Your code doesn't compile:

        $ perl -cw 1152653.pl
Global symbol "$in" requires explicit package name at 1152653.pl line 
+9.
Global symbol "$in" requires explicit package name at 1152653.pl line 
+11.
Missing right curly or square bracket at 1152653.pl line 14, at end of
+ line
syntax error at 1152653.pl line 14, at EOF
1152653.pl had compilation errors.

        [download]

        You'll need to fix the errant opening brace and the scoping of $in.

        Update: Here's a working rewrite of your script above:

        use strict;
use warnings;
open my $in, '<', '1.txt' or die "Cannot open 1.txt: $!";
while (my $file = <$in>) {
    $file =~ s/..![^!]*something.*\.c//;
    print $file;
}
close $in;

        [download]

        And here's what happens when I run it:

        $ cat 1.txt
foo
?!?!?!/pack/something/whatever.cacshdska
bar
$ perl fixup.pl 
foo
?!?acshdska
bar

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Re: special pattern reading
by Anonymous Monk on Jan 13, 2016 at 09:49 UTC
[reply]

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