BenV's notes » perl

Necta.pl lives again!

BenV — Sat, 10 Apr 2010 16:35:17 +0000

When nectarine died a few years ago (or at least, that’s how I view it) with their broken harddisks, lost backups and whatnot, I gave up on the necta.pl tool me and a friend of mine had written.
However, a few months ago I got back into listening to the new scenemusic.eu who got everything back up and running based on recovered data from the old Nectarine.
It seems like they did a proper job of setting up a new site, and they even provide a nice xml backend for tools like this.

So after a while I decided to revive our tool. This time I took the time to curse even more at Irssi and their script support, so I implemented the nonblocking fetcher and nectarine parser
in separate libraries. Well, isn’t that fun. Reloading those things was a problem (/script load necta wouldn’t reload those underlying libraries), but fortunately Garion helped me out here after a mail to the Irssi mailing list. Thanks Garion!

Anyway, I’ve put the first release up for download on this page:
http://notes.benv.junerules.com/necta/

Or a direct link to the download:
Irssi Necta script v0.01 - Version 0.01 - SHA: 62f7c4994750dac154807f2be43c85a8d2020182

Let the bug report begin

dos2unix

BenV — Fri, 21 Aug 2009 17:41:37 +0000

Another annoying thing: morons that save their files with dos line endings.
Also known as “I’ve got motherfucking ^M in my file, AAAIIEEEEYGGrrgrll“.
I usually find out about this when bash complains about stuff like this:

benv@janeman:~$ ./bla.pl
-bash: ./bla.pl: /usr/bin/perl^M: bad interpreter: No such file or directory

(HAAAAAT!!!)

Solution:

benv@janeman:~$ vim kankerfile
:set fileformat=unix
:wq

(Don’t confuse fileformat with filetype, one is used for encoding, the other for things as syntax highlighting)

Solution 2:

benv@janeman:~$ dos2unix kankerfile

I never use this since I never have that piece of cancer called dos2unix, but some distros do.

Solution 3:

sed -ie 's/\r//g' bla.pl

That should fix it. On to the “let’s trash my home directory with my fancy new perl script that I just converted”

(n)Curses magic part 2: magic!

BenV — Sat, 08 Aug 2009 16:15:00 +0000

So while messing around with some perl/curses stuff I got fancy with colors and soon found out about the limited support of colors in terminals and therefore also Curses.
Anyway, I made this little “fractal plasma” thingy with it, see if you can get it running
It’s not really a fractal plasma, so don’t get technical on that, but it describes it best I think.

To get it running, open up your favorite terminal that supports 256 colors and allows palette changing – I found both xterm and urxvt to work.
Make sure your TERM variable is set to something that allows this, for instance in urxvt:

$ export TERM=rxvt-256color
$ ./fractplasm.pl

or this worked for me with xterm:

$ export TERM=xterm-256color
$ ./fractplasm.pl

Something like this is the result:

fractplasm.pl - Version 0.1 - SHA: 83086edd86b25eed5fddcbbf6beaae53924e06f6

Enjoy!

(n)Curses magic: are you a magician?

BenV — Fri, 07 Aug 2009 14:39:13 +0000

Hej readers,

I decided to work on making slackbuild.pl a bit more acceptable in terms of usability and looks. The reason for this is that the dialog program doesn’t exactly do what I want.
That is, it works…. but that’s pretty much all I can say about it. It doesn’t allow me to make a comined checkbox/menu thing that I want for my configure options part. Next to that it’s tedious to fork and parse its output all the time, and let’s not even get started about looks and input issues.
So I figured: hmm, dialog is made in ncurses, perl has a Curses lib…. let’s play!

First off I read through most of NCURSES Programming HOWTO. Somehow it felt familiar, probably because I already went through it when messing with iotop. Next, I realized that google is pretty much useless when you try to search for ‘curses’ and perl, probably because it’s the misspelled version of ‘cursus’ which means ‘course’ in dutch. However, ncurses is something you can search for and find -some- (but few) bits and pieces of information.

Time for a hello world.

#!/usr/bin/perl
use Curses;

# init curses
initscr();
noecho();
start_color();
init_pair(1, COLOR_CYAN, COLOR_BLACK);

# Print some stuff and wait for user input
attron(COLOR_PAIR(1));
addstr(1, 5, "Hello, world!\n");
getch();

# Cleanup and end
endwin();

And we run this, and voila:

Well, that was easy enough. Of course I already knew all this shit, I made iotop after all…
Now time for more advanced trickery: windows.
What I want is simple: tailbox, yesnobox, checkboxconfigureoptionsthingy and all that with some good style.
“YOU SAID SIMPLE!”
Well, I never said it would be easy

So my idea was to make the stdscr the backtitle, should be easy enough to always paint that the same way right?
And then make the other things windows above that. Now the mysteries start.
A little code to test the windowing concepts:

#!/usr/bin/perl
use Curses;

# init again
initscr();
noecho();
cbreak(); # no waiting for enter anymore on getch
start_color();
init_pair(1, COLOR_CYAN, COLOR_BLACK);

# make some windows that overlap
my $win = newwin(20, 40, 10, 10);
my $win2 = newwin(20, 40, 5, 5);

# some text in them
addstr($win, 1, 1, "World!");
addstr($win2, 1, 1, "Hello");

# give them borders
attrset($win, COLOR_PAIR(1));
box($win, '|', '-');
attroff($win, COLOR_PAIR(1));
box($win2, '|', '-');

# Show them! (in correct overlapping order!)
refresh($win2);
refresh($win);

# Make user press 'q' this time
my $key;
do {} while (($key = getch()) ne ERR && $key ne 'q');

# cleanup and exit
delwin($win2);
delwin($win);
endwin();

And here’s our beautiful result:

…. what the.
Our window is empty?
But how could this be?
MAGIC!!!!
However, it does wait for the ‘q’ button before exiting, so not everything failed…

This sort of nonsense is exactly the reason why I started this post. Right now I’m having some serious doubts about continuing this curse*COUGH*s project, but on the other hand, it’s a nice challenge. Probably one of the reasons dialog is such a piece of junk… the library is garbage!
Note that there are a few other options, such as Curses::UI, but they seem to be a bit more junk than I want, not to mention another depedency. Nah, I’ll figure it out using Curses for as long as I can manage to not go crazy.

Some pointers I found out:

Printing stuff outside a window (because the window is too small) makes it go bonkers. It might not appear at all, overwrite other stuff… you name it.
A big pitfall is the y,x syntax. Where one would expect coordinates in the x,y format, curses makes you curse and reverse.
Another pitfall is forgetting the refresh, or messing up the order of the refreshes. I’m writing some wrappers for that in slackbuild.pl.
Overlapping windows are another source of fun, in order to make sure the overlapped window gets repainted properly you can use touchwin($win); on it.

Oh yeah, if you ever decide to write a curses program:
Make sure to set a __DIE__ handler that RESTORES THE TERMINAL PROPERLY! If one thing annoys people it’s messing up their stuff…. and not closing Curses properly does exactly that.
For those who wonder how to get out of such a broken terminal, type in ‘reset‘ and hit enter. (or twice if you’re a bad typist). No, this won’t reset your pc, it will simply reset your terminal to sanity.

“But what about the broken code in the second example?”
Oh yeah… another case of forgetting to call refresh. What we did there was to properly refresh the imaginary windows.
However, we forgot to refresh the real stdscr window that contains them! So nothing was output to the screen. Lovely.
It’s still a bit fuzzy here though, so don’t mind me if I screwed up the reasoning, but that’s what I understand about it now. It’ll get better
Anyway, insert a refresh(); at line 25 and it’ll do what you’d expect. It’ll look like this:

Good luck with your cursed rabbits!

***followup here:ncurses magic part 2***