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binmode can save your bacon
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by poltr1
on Feb 28, 2015 at 02:02

    Another "war story" here -- not a question, but something worth passing on: A previous client of mine had some Summit and Zeiss precision measuring (i.e. metrology) machines, and about 6,000 programs to perform measurements on the various parts this company manufactured. They were in the process of migrating network operating systems (from Novell to Microsoft), and thus, had to change the hardcoded drive mappings in these files. All 6,000 of them.

    No way was I going to do this manually. (Laziness, y'know?) I could write a perl script to perform a search-and-replace mission. And I did. But there was another problem: the script wasn't finding the filepaths based on the regex I wrote. So I then did a hexdump on a couple of these files. That's when I discovered the files were in binary format, but the filepaths were plain-text. What was I to do? RTFD. I came across the binmode command, which enabled me to open up files in binary format. So I tried it. And it worked -- it finally matched the regex, and replaced the old drive mapping with the new path.

    binmode FILEHANDLE;

    But there were still some paths that didn't get converted. These were mostly for external shape definition files, and comprised about 10% of the total set of programs. So I called the vendor to see if they had a product to do what we wanted to do. And the vendor told me "it couldn't be done". I knew otherwise, but I wasn't going to tell the vendor that they were wrong.

    Bottom line: Using binmode, Perl can be used to edit binary files. But Be Careful How You Use It!

Color highlighted perl grep
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by FreeBeerReekingMonk
on Feb 23, 2015 at 12:49

    To highlight a grep, we use grep --color, however, sometimes either grep does not have highlighting (AIX), or, we want to highlight multiple expressions with different colors.

    usage: ls -l | grep -e foo -e bar |./ this that foo bar

    #!/usr/bin/perl use Term::ANSIColor; while(<STDIN>){ for $i (1..15){ next unless(defined($ARGV[$i-1])); s/($ARGV[$i-1])/&colored($1,"ansi15 on_ansi$i")/gexi; } print; }

    Of course, just use an alias or put it in the path and call it just "hl" for sanity. It supports 15 different arguments, but can be extended to the 255 different combinations Linux has. On some terminals however, you want your own selected colours, in that case, you will need to specify them by hand, for example:

    #!/usr/bin/perl use Term::ANSIColor; $VERSION = '1.1'; @C = ('black on_yellow','black on_green','black on_cyan','black on_red +', 'red on_white', 'black on_magenta', 'white on_red', 'white on_blue +', 'blue on_white', 'yellow on_cyan' ); while(<STDIN>){ for $i (0..$#C){ s/($ARGV[$i])/&colored($1,$C[$i])/gexi if($ARGV[$i]); } print; }

    In the latter example, you can specify many more attributes, like bold and underscore, even blink... peruse for examples.

    Caveats: Do not grep on digits 0..15 (except as first argument), as the ansi codes also contain numbers...

random file script
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by etherald
on Jan 30, 2015 at 23:50
    here's my random file script to recursively choose a number of random files matching a regex from a directory or list of directories
    #!/usr/bin/env perl # recursively choose a number of files optionally matchinng a regex # from a directory or list of directories. defaults to cwd. # outputs absolute paths by default, relative with -r # use like so: # randomfile -n 23 -p \(mp3\|ogg\|flac\)$ ~/music ~/music2 use strict; use warnings; use Getopt::Long; use Cwd; use File::Random qw/random_file/; use File::Spec; my $pat = '^.+$'; my $num = 1; my $relative = 0; GetOptions( 'p|pattern=s' => \$pat, 'n|number=i' => \$num, 'r|relative' => \$relative, ); while ($num) { my $random_file; my $dir; do { $dir = $ARGV[rand @ARGV] or cwd(); $random_file = random_file( -dir => $dir, -check => qr/$pat/, -recursive => 1); } until $random_file; $random_file = "$dir/$random_file"; $random_file = File::Spec->abs2rel($random_file) if $relative; print "$random_file\n"; --$num; }
Alphabetize in Esperanto
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by aplonis
on Jan 30, 2015 at 10:21

    A hobby of mine is translating Jack Vance into Esperanto. And yes, I have permission for this! These I distribute for free in EPub format. In each ebook I like to embed a mini linked-in dictionary to help out beginners.

    I was wanting to re-organize some standalone EPubs into one omnibus EPub. I wanted one end-of-book dictionary instead of six end-of-chapter ones. That meant re-alphabetizing hundreds of anchor links. No big deal to do it in Perl...except that it's Unicode...and Esperanto. Here's how I did it.

yellow pages
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by japh2963
on Jan 29, 2015 at 01:32

    was looking for freelance work and came across a request for a script that would scrape yellow pages website. Hopefully the poster will google more before they spend $300 bucks for this...


    #!/usr/bin/perl # program: # purpose: search for phone number on # date: 2015.01.28 use strict; use warnings; use LWP::Simple; my $usage = "\n\tusage: perl $0 [PHO-NEN-UMBR]\n"; my $baseUri = ''; my $phoneNumber = $ARGV[0]; die $usage unless($phoneNumber =~ m/^\d{3}-?\d{3}-?\d{4}$/); my $content = get("$baseUri$phoneNumber"); $content =~ s/\s+/ /g; $content =~ s/\&nbsp;/ /g; $content =~ s/>\s*</\n/g; my $hits = 0; foreach my $e(split /\n/, $content){ chomp $e; if($e =~ m/^.*itemprop=['|"](\S+)['|"].*>(.*),?<\/\S+.*$/i){ my $itemProp = $1; my $itemValue = $2; $itemValue =~ s/,\s*$//; print "$itemProp: $itemValue\n"; $hits++; } } print "no results found for number '$phoneNumber'\n" if(!$hits); exit;
MD5 checksums for Windows
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by golux
on Jan 13, 2015 at 11:58
    This program "" (for Windows) generates checksums matching those produced by the "md5sum" program in Linux. I wrote it because I often need to validate whether 2 files on different computers are the same.

    Enter "" without arguments for a syntax message. Both files and/or directories (ie. "folders") are accepted as arguments. With the switch -R subdirectories are searched recursively. The switches -s <key> and -r control how the output is sorted. The -d switch gives a final report of any duplicate checksums found.

    Hope this might be of general use to others as well!

    Update:   At Anonymous Monk's suggestion, I've added a "-c" switch which produces a checksum format compatible with "md5sum". It does this by skipping the filesize, and prefixing the path with '*' to signify that the checksum was done in binary mode.

    say  substr+lc crypt(qw $i3 SI$),4,5
How to perldebug a Term::ReadLine application
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by LanX
on Dec 01, 2014 at 09:42

    the problem

    I recently heard monks complaining that applications using Term::ReadLine can't be debugged within the perldebugger b/c it's interface relies on Term::Readline.

    the trick

    here one solution (at least for linux) I wanted to have documented (before I forget it again ;)

    call the script you want to debug (here ) from a shell with

    PERLDB_OPTS="TTY=`tty` ReadLine=0" xterm -e perl -d ./

    and a second xterm will be opened running the program.

    how it works

    a second xterm is started running the debugger, but b/c of the TTY setting in PERLDB_OPTS all debugger communication goes via the parent xterm , while the calc app normally displays in the child xterm .

    ReadLine=0 tells the debugger not to rely on a working Term::ReadLine.

    NB: It's important that calling the second xterm blocks the execution in the first xterm till it's finished. Like this keystrokes aren interpreted by two applications in the first xterm. Just put an & at the end to see how things get messed up otherwise if the shell tries to step in.

    how it looks like

    first xterm

    becomes the front end for the debugger

    as you see I get the lines from the app in the second xterm listed can set a breakpoint at the end of the loop and tell twice to continue till next breakpoint.

    second xterm

    runs the application, I'm asked to enter a calculation which is evaluated, interupted twice by a breakpoint at line 9.

    Enter code: 1+2 3 Enter code: 4+4 8

    the test script

    > cat ./ use Term::ReadLine; my $term = Term::ReadLine->new('Simple Perl calc'); my $prompt = "Enter code: "; my $OUT = $term->OUT || \*STDOUT; while ( $_ = $term->readline($prompt) ) { my $res = eval($_); warn $@ if $@; print $OUT $res, "\n" unless $@; $term->addhistory($_) if /\S/; }

    tested with Term::ReadLine::Gnu installed.


    you can use this approach whenever you want the debugger communication separated into a separate term. e.g. Curses::UI comes to mind


    the solution is not "perfect", of course you need to arrange the windows and switch with Alt-Tab between them. (maybe screen could solve this or an emacs inegration)

    Furthermore you won't have a history with arrow navigation within the debugger, cause TRL was disabled.

    another approach is to communicate via sockets with a debugger run within emacs, since emacs has it's own TRL-emulation this shouldn't interfere.

    see also Re: Testing terminal programs within emacs (SOLVED) for an approach to handle all this automatically, by restarting a script with altered environment and different terminal.


    see perldebguts , perldebtut and perldeb,

    Also "Pro Perl Debugging" book and various TK tools on CPAN.

    Cheers Rolf

    (addicted to the Perl Programming Language and ☆☆☆☆ :)

The hills are alive...
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by Lady_Aleena
on Nov 26, 2014 at 22:25

    ..with The Sound of Music. ;)

    I had @SoM_notes and $SoM sitting around doing nothing, so this evening, I made them do something. In make_SoM_song and get_SoM_def, you enter a string of alphabetical notes (c, d, e, f, g, a, b). The notes can be separated by a comma, semicolon, or a space. The functions will return the note name given by Maria von Trapp in The Sound of Music.

    I wrote random_SoM_note and random_SoM_song because I couldnt' help myself. Most of you know how much I love to randomly generate things. :)

    make_SoM_song, get_SoM_def, and random_SoM_song all return array references.

    Enjoy the code!

    package SoundofMusicSong; use strict; use warnings; use Exporter qw(import); our @EXPORT_OK = qw(make_SoM_song get_SoM_def random_SoM_note random_S +oM_song); my @base_notes = qw(c d e f g a b); my @SoM_notes = qw(do re me fa so la te); my %notes; @notes{@base_notes} = @SoM_notes; my $SoM = { 'do' => 'a deer a female deer', 're' => 'a drop of golden sun', 'me' => 'a name I call myself', 'fa' => 'a long long way to run', 'so' => 'a needle pulling thread', 'la' => 'a note to follow so', 'te' => 'a drink with jam and bread', }; sub make_SoM_song { my ($user_song) = @_; my @song_notes = split(/[ ,;]/, $user_song); my @new_song = map { $_ = $_ =~ /^[a-g]$/ ? $notes{$_} : 'not a note +'; $_ } @song_notes; return \@new_song; } sub get_SoM_def { my ($user_song) = @_; my $notes = make_SoM_song($user_song); my @new_song = map { $_ = $$SoM{$_} ? $_.' '.$$SoM{$_} : 'not a note +'; $_ } @$notes; return \@new_song; } sub random_SoM_note { my $note = $SoM_notes[rand @SoM_notes]; return $note; } sub random_SoM_song { my ($number_of_notes) = @_; my $notes = $number_of_notes ? $number_of_notes : int(rand(100)) + 1 +; my @new_song; push @new_song, random_SoM_note for (1..$notes); return \@new_song; } 1;
    No matter how hysterical I get, my problems are not time sensitive. So, relax, have a cookie, and a very nice day!
    Lady Aleena
CPAN Namespace Navigator
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by Discipulus
on Nov 25, 2014 at 06:23
    CPAN Namespace Navigator is an interactive program that let you to navigate all namespaces on CPAN.
    The idea born when i read that before upload something to CPAN is better to explore existing modules, but when i asked here in the chat how to browse it i discovered that ther is not a real exploration program to do it.

    So the challenge was to hack directly the fomous file 02packages.details.txt that we receive (gzipped) when we search some module with some CPAN client. I used Term::ReadLine not without some headache.

    I decided (unwisely) to eval directly the data received to build up a big HoH with the whole hierarchy of CPAN modules and reletad infos. As suggested (wisely) by ambrus and yitzchak i looked at tye's Data::Diver and on my own at an ancient and unmaintained Data::Walker one.

    I was not able to bind Data::Diver at my will to add to the structure others infos like parent namespace or version, so i reinvented that wheel evaluating everything by myself.

    Surprisingly it worked.

    This is the usage and the navigation commands available during the navigation:
    USAGE: [02packages.details.txt] NAVIGATION: . simple list of contained namespaces .. move one level up + detailed list of contained namespaces * read the readme file of current namespace ** download the current namespace's package ? print this help TAB completion enabled on all sub namespaces by Discipulus as found at
    And here you have the code, finally crafted after 37 steps of development.


    update: take a look also at Re: Autocomplete in perl console application
    There are no rules, there are no thumbs..
    Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.
Archive by month and extension
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by GotToBTru
on Nov 24, 2014 at 16:01

    Created the following to archive data from our applications. We archive by month, and by file extension, so those are built in assumptions in this program.

    Source Code:


    1 Peter 4:10
img - display a small graphic file at the command line
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by sflitman
on Nov 22, 2014 at 21:21

    I do a lot of work in Putty and need to look at icon files sometimes. I thought it would be cool to get Putty to display them in bash directly, rather than using X11 forwarding. This is not meant to be any kind of substitute for real graphics, but is a quick way to see whether a particular image file (like an icon or a web button) is what I think it is. Note that it requires 256 color to be turned on in Putty, that your Terminal setting is putty-256color, and it only handles image formats handled by GD (png, jpg, gif).

    #!/usr/bin/perl # Steve Flitman - released to Public Domain - display a small image on + the console using 256-color mode Putty/Screen # Color output to terminal derived from Todd Larason < +> use strict; use warnings; use GD; unless (@ARGV) { die "img file ...\nDisplay files at command line using ANSI 256 col +or mode\n"; } # set colors 16-231 to a 6x6x6 color cube for (my $red=0; $red<6; $red++) { for (my $green=0; $green<6; $green++) { for (my $blue=0; $blue<6; $blue++) { printf("\x1b]4;%d;rgb:%2.2x/%2.2x/%2.2x\x1b\\", 16 + ($red * 36) + ($green * 6) + $blue, ($red ? ($red * 40 + 55) : 0), ($green ? ($green * 40 + 55) : 0), ($blue ? ($blue * 40 + 55) : 0)); } } } # colors 232-255 are a grayscale ramp, intentionally leaving out black + and white for (my $gray=0; $gray<24; $gray++) { my $level=($gray * 10) + 8; printf("\x1b]4;%d;rgb:%2.2x/%2.2x/%2.2x\x1b\\", 232 + $gray, $level, $level, $level); } my ($file,$x,$y,$r,$g,$b,$color,$index,$image,$width,$height); for $file (@ARGV) { die "Cannot read $file: $!\n" unless -r $file; my $image=GD::Image->new($file); die "Not a recognized image format: $file\n" unless defined $image; my ($width,$height)=$image->getBounds(); for (my $y=0; $y<$height; $y++) { for (my $x=0; $x<$width; $x++) { my $index=$image->getPixel($x,$y); my ($r,$g,$b)=$image->rgb($index); if ($r+$g+$b==0) { # black $color=0; } elsif ($r==255 && $g==255 && $b==255) { # white $color=15; } elsif ($r==$g && $g==$b) { # grayscale $color=232+($r>>3); } else { $color=16+(int($r/42.6)*36)+(int($g/42.6)*6)+int($b/42.6); + # smush 256 color range to 6 levels } print "\x1b[48;5;${color}m "; } print "\x1b[0m\n"; # reset } print "\x1b[0m\n"; # reset } exit;

    Dedicated to the memory of John Todd Larason,



NSA's FoxAcid
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by morgon
on Nov 20, 2014 at 09:49
    According to various top-secret documents provided by Snowden, FoxAcid is the NSA codename for what the NSA calls an "exploit orchestrator," an internet-enabled system capable of attacking target computers in a variety of different ways. It is a Windows 2003 computer configured with custom software and a series of Perl scripts.


    It may stretch the definition of "cool" and may be old news but maybe a few monks will find this amusing...

read file a paragraph at a time and return paragraph OR get specific data from paragraph
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by james28909
on Nov 02, 2014 at 16:10
    i have figured out how to read a file a paragraph at a time :D lol. in this example i will be reading a file a paragraph at a time and then getting only certain data back.

    this will return everything AFTER the pattern up until a newline very quickly for me but prob could be done faster by a seasoned coder. you can modify it to suit your needs hopefully.
    tested with active perl and win7 ultimate x64
    $/ = ""; #set to paragraph mode while(<$file>){ if ($_ =~ /$first_match/ && $_ =~ /$second_match/ && $_ =~ /$third +_match/){ print "$_\n"; my ($needed_data_0) = (/^data_here(.+)/, $_); my ($needed_data_1) = (/^more_data(.+)/, $_); my ($needed_data_2) = (/^other_data(.+)/, $_); print "data0 is: $needed_data_0\n"; print "data1 is: $needed_data_1\n"; print "data2 is: $needed_data_2"; } }
    any input or pointers are welcome.
Random video player
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by james28909
on Oct 29, 2014 at 14:02
    this little script will use file random to get a video file and will use your player of choice to launch it. mediainfo.exe was used to get sleep count.

    if you see anyway i can improve it please make a comment. i am trying to figure out how to push the filename to an array and do a check if it has played it in the last 100 videos/loops(that would help keep it from repeating if it does i think). i would also like to specify how many times to loop before exiting, that way it doesnt just loop forever and ever and the user can specify how many shows they want to watch.

    i wasnt please with the way i had to get duration, but it worked and i was astounded, so if you have of a better was to get duration time, please let me know. the problem i was dealing with while getting duration with any tool was spaces in the path/filenames. Here is the code:
    use strict; use warnings; use diagnostics; use File::Random qw(random_file); my $dir = $ARGV[0]; if ( not defined $dir ) { print "\nUsage: [folder]; exit(0); }else{ random($dir); } sub random{ my ($dir) = @_; while (1){ my $mpc = "C:/Program Files (x86)/K-Lite Codec Pack/Media +Player Classic/mpc-hc.exe"; my $rndm_file = random_file( -dir => $dir, #-check => qr/./, -recursive => 1 ); if ($rndm_file =~ /\.(ini|nfo|db)$/i){ print "$rndm_file\n"; random($dir); } print $rndm_file; #get duration my $t = ("MediaInfo.exe --Output=Video;%Duration% \"F:/TV/ +$rndm_file\""); system(1, $mpc, "F:/TV/$rndm_file"); my $time = qx($t); my $sleep_time = $time/1000; #in seconds because m +ediainfo.exe outputs milliseconds i think. print "\nDuration in seconds: $sleep_time\n"; sleep($sleep_time); random($dir); } }
    this works great if you have a ton of media in a folder and want to randomly watch any given inside in that directory, and you do not have to worry about spaces in path/filenames. and this is also for windows but i think it could be used on any other platform as well with small changes
Using Data::Compare recursively to better identity differences between hashes
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by Lady_Aleena
on Oct 18, 2014 at 01:49

    Yesterday I wanted to compare two hashes to see if they were the same. I looked around a little bit and found Data::Compare. It was good at telling me the two hashes were different, however, it did not tell me where. So, I wrote a small little subroutine to recursively check my hash of hashes (of hashes). It was able to identity where I had to look to make corrections, almost to the exact spot. (I am unsure how to compare arrays of hashes just yet which is why the following little subroutine will almost take you to the right spot.)

    There are still holes in the script, but it worked for me today.

    #!/usr/bin/perl use strict; use warnings FATAL => qw( all ); use Data::Compare; use Data::Dumper; # You can take out all instances of the subroutine 'line' to print wha +t you want in those places. sub deep_data_compare { my ($tab, $old_data, $new_data, $data) = @_; my $old = $old_data; my $new = $new_data; my $compare = new Data::Compare($old, $new); if ($compare->Cmp == 0) { line($tab,$data) if $data; if (ref($old) eq 'HASH' && ref($new) eq 'HASH') { line($tab+1,'old to new'); for (keys %$old) { deep_data_compare($tab+2,$_,$$old{$_},$$new{$_}); } } # I have not figured out this part yet. # elsif (ref($old) eq 'ARRAY' && ref($new) eq 'ARRAY') { # } else { print Dumper($new); print Dumper($old); } } } sub rline { my ($tab,$line) = @_; return qq(\t) x $tab.qq($line\n); } sub line { print rline(@_); } deep_data_compare(0, \%old_hash, \%new_hash, 'widgets');
    No matter how hysterical I get, my problems are not time sensitive. So, relax, have a cookie, and a very nice day!
    Lady Aleena

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