Please Explain Code

costas1 has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Please Explain Code by marto (Cardinal) on Sep 22, 2011 at 15:06 UTC
The first thing you should read is perlintro, which covers a lot of the very basics and includes links to more detailed documentation. Other great resourses for learning Perl include: http://learn.perl.org http://perldoc.perl.org The Tutorials section of this site.	[reply]
Re^2: Please Explain Code by pat_mc (Pilgrim) on Sep 22, 2011 at 15:32 UTC
Wow ... this is definitely one of the most helpful and accommodating ways I have seen around here for saying: Go and do your homework yourself ... and I don't mean this in a bad way. Good on ya!	[reply]
Re: Please Explain Code by choroba (Cardinal) on Sep 22, 2011 at 15:10 UTC
`my ($fin, $dt, $vard );`Declares scalar variables. See my and perldata. `my %anc = ();` [download] Declares a hash variable. See perldata. `my %cnt = ();` [download] See line 2. `my @myfiles =();` [download] Declares an array. See perldata. `my @all = ();` [download] See line 4.Empty line. Has no effect. `@myfiles=<A> or die "No files to open A\ for reading. $!";` [download] Search for files whose names start with A. If there are any, store the names to the array, if not, stop the program and complain.Empty line. `foreach $fin (@myfiles) {` [download] Beginning of a loop. See perlsyn. `##my $fin="A20100222.1700-1715_GWLD1E_1.xml";` [download] Comment. Has no effect. `open INP, "$fin" or die "Cannot open $fin for read :$!";` [download] Opens a file for reading, if it's possible. See open. `$fin =~ (/^A(\d{8}).(\d{4})/);` [download] Matches the file name against a regular expression. See perlre and perlop. `my $dt = "$1" . ":" . "$2";` [download] Dot is the concatenation operator. `#print "$dt\n";` [download] Comment. `while (<INP>) {` [download] Another loop. `if (/^<moid>.*=(\d+)</) {` [download] Condition. `$anc{$1} += 1;` [download] See perlop. `}` [download] `elsif (/^<mt>(.+)</) {` [download] If the first condition was not true, try this one. `$cnt{$1} += 1;` [download] `}` [download] `elsif (/^<\/md>$/) {` [download] `last;` [download] Exit the innermost loop. `}` [download] End of the loop. `}` [download] See the previous line. `close (INP);` [download] Close the filehandle. `}` [download] `open(OUT, ">>all_announc_cnt.txt") or die "Cannot open all_announc_cnt +.txt file for writting :$!";` [download] Open a file for writing (appending). `foreach $vard (sort {$a <=> $b} (keys(%anc))) {` [download] See sort, keys. `print OUT "$vard:$anc{$vard}\n";` [download] See print. `}` [download] `print OUT "\n";` [download] `foreach $vard (sort (keys(%cnt))) {` [download] `print OUT "$vard:$cnt{$vard}\n";` [download] `#push (@all, "$vard:$anc{$vard}");` [download] `}` [download] `close (OUT);` [download]	[reply] [d/l] [select]
Re^2: Please Explain Code by pat_mc (Pilgrim) on Sep 22, 2011 at 15:34 UTC
I admire your patience ...	[reply]
Re: Please Explain Code by pat_mc (Pilgrim) on Sep 22, 2011 at 15:38 UTC
Just as a general comment: Most monks around here don't respond very favourably to people copying and pasting Perl code they have found somewhere on the web without putting any effort into trying to understand at least the bare minimum of it themselves. You should be able to answer most of your questions after spending about 1 - 3 hrs on some basic Perl tutorials (depending on your background in other programming languages). If you have never done any programming before, start with the llama book ... it is great fun to read and will get you a long way towards answering all the questions you asked. It may only take you a little longer. Good luck! P. S.: And yes, this is probably one of my less helpful posts in this forum.	[reply]
Re^2: Please Explain Code by costas1 (Initiate) on Sep 22, 2011 at 16:24 UTC
I realised it wouldnt be the most insighful post out there,thats what the err refers to... I guess I was a bit vague myself as I do understand a few things and have put in some effort; I just have an old script that does some batch text process and could save me quite a few hours on VB if only I knew a few more things. So I thought it couldnt hurt to ask. Anyway I now realise my post was quite rude so sorry for that. Thank you for you wisdom.	[reply]
Re^2: Please Explain Code by misterwhipple (Monk) on Sep 22, 2011 at 18:23 UTC
For those who don't yet know, the llama book is Learning Perl by Randal L. Schwartz, brian d foy, and Tom Phoenix. -- Any sufficiently interesting Perl project will depend upon at least one module that doesn't run on Windows.	[reply]