Thursday 31 August 2006

ASCII character conversion

The od command can be used after a fashion to convert from a character to its character code:

 echo -ne "A" | od -t u1 | sed -e "s/^[0-9]* *//"

But more awkward is converting from a decimal character code back to the character, but this does the trick, and took about 3 minutes to come up with:

$ X=65
$ HEX=(0 1 2 3 4 5 6 7 8 9 a b c d e f)
$ echo -e "x${HEX[$(( $X / 16))]}${HEX[$(( $X % 16 ))]}"

It works by converting which is less than 255 to hexadecimal, and then making use of echo -e which interprets \x as indicating an 8 bit character expressed in hexadecimal.

Tuesday 1 August 2006

Online Textbooks

Like many geeks I collect knowledge so that I will be able to do things if the need comes up, whatever things they are. Here’s a good list of refererences books supplied by nTensify who wrote:

There are a lot of free textbooks out there, some of them are better than others, but a lot are quickly becoming very good.

Plain and simple, everyone should have access to education, money shouldn’t dictate how educated someone can become.

Some other free books: (three physics books from beginning physics to general relativity). (six physics books, variety of topics) (notably one of the best free physics books ever "published"). (intro to calc book under Creative Commons) (a really cool free circuit design book I ran across a few years ago when I was leaving college). (obligatory gutenburg link, aggrigator of books out of copyright or otherwise set free).

(there are plenty more, but to spare you the boredom of a huge list here… go to google and search for digital library books, you’ll have a few million hits to look through ;) )