Sunday, 20 April 2008

bash fun vol. 2

Forget previous post. Bash has functions: goj@abulafia ~ $ tail ~/.bashrc
function apply() {
for x in $*; do $cmd $x; done

function go() {
cd ${!#}

Much better now. :)

Monday, 14 April 2008

bash fun

Quote by Terrence Parr:
My Motto: "Why program by hand in five days what you can spend five years of your life automating?"

We do a lot of actions that make a directory interesting for us and then we want to cd intro that directory. Consider:

hg init my_repo; cd my_repo
mkdir -p a/b/c/d; cd a/b/c/d
mv my_file /tmp; cd /tmp

Boring, repetitive and not DRY.

Lesson 1: You can do something like this:
mkdir -p a/b/c/d; cd !$

Better, but not good enough for me. I'd like to type
go hg init my_repo
go mkdir -p a/b/c/d
go mv my_file /tmp

So we need to create a short bash script, don't we?

How do we get last argument of the script (we'll need that). Provided that $1 is the first argument, $2 - second and $# - argument count and $@ all arguments as an array... yes, you guessed it. It's ${!#}

How nice and intuitive. Try those: $$# ${$#} ${${#}} $@[$#].

So do we have all that we need?
goj@abulafia tmp $ cat go
cd ${!#}

goj@abulafia tmp $ ./go echo ~
goj@abulafia tmp $

Epic FAIL. ./go script is executed in child shell. When it terminates it's parent's CWD is unaffected. We have to source it:

goj@abulafia tmp $ . ./go echo ~
goj@abulafia ~ $

But this syntax sucks. Luckily, alias is our friend:

goj@abulafia tmp $ echo 'alias go=". go-source-me"' >> ~/.bashrc
goj@abulafia tmp $ mv go ~/bin/go-source-me

You have to have ~/bin in your PATH.

goj@abulafia tmp $ go echo ~
goj@abulafia ~ $


Wednesday, 2 April 2008

April Fool's day

As last year, I managed to make my year's forum unreadable for April Fool's day. Awful, pink theme from last year was yesterday joined by truly horrible spelling and flipped avatars. :>

Here are the results:

Here is a little HOWTO. It may be useful for something practical, or for next year. Basically, you have to use mod_ext_filter see the sed example.

Polish spelling mistakes are different to English ones. They are (mostly) caused by fact, that there are (for historical & (maybe) other slavic languages "compatibility" reasons (is legacy a proper word?)) few sounds that have the two spellings, like ź-rz and u-ó, h-ch. It makes it very easy to inject typos to polish text.

We are talking about HTML pages. You cannot break html, eg <a chref="..."> would be BAD. So we don't touch anything inside html tags, comments and entities. This makes it hard to use regexps. If I were to write this joke's filter program once again I would use flex. But I wrote a short and slow (2,2 seconds to process a page - unacceptable) automata-based python script, and then (when it turned out how bad it performs) added lighting-fast (0,01 s/page) C-code generation to it. Generating code for automata is very easy.

code is here

Code generation itself is a bit over-engineered, too. I shouldn't have cared about beautiful indentation & proper newlines. I should have used GNU indent instead.

Apache configuration:
ExtFilterDefine ortozawal mode=output intype=text/html cmd="/usr/local/bin/ortozawal"
ExtFilterDefine ungzip-filter mode=output intype=text/html cmd="/bin/gunzip -"
ExtFilterDefine gzipme-filter mode=output intype=text/html cmd="/bin/gzip"
ExtFilterDefine flip-image mode=output cmd="/usr/bin/convert - -flip -"

<Location "/forum">
SetOutputFilter ungzip-filter;ortozawal;gzipme-filter

<Location "/forum/images">
SetOutputFilter flip-image

gunzip-filter-gzip is a filthy trick. You can probably avoid it by proper filter configuration. If you know how, please drop me a comment.