Un naufragio personal

Cálculo de la letra del NIF español, en una línea de shell script

 nif() { echo $1$(expr substr TRWAGMYFPDXBNJZSQVHLCKET $(($1 % 23 + 1)) 1) ; }

Acepta como primer argumento el número de NIF (sin ceros por delante, si los llevara). Útil para añadir a ~/.bashrc.

How To Verify CD-R Data Retention Over Time?

The following two interesting tools are referred there:

par2 - PAR 2.0 compatible file verification and repair tool

"par2 is a program for creating and using PAR2 files to detect damage in data files and repair them if necessary. It can be used with any kind of file."

dvdisaster - data loss/scratch/aging protection for CD/DVD media

"dvdisaster provides a margin of safety against data loss on CD and DVD media caused by scratches or aging media. It creates error correction data which is used to recover unreadable sectors if the disc becomes damaged at a later time."

Dvdisaster approach is specially interesting, as it can append its error correction information to an existing .iso file, using as much space as available to fill the smallest medium size (CD, DVD or DVD9). That information seems to be invisible, so it does not interfere with the media content.

 dvdisaster -i cd.iso -mRS02 -c

More on Apache's mod_rewrite


What I use here to emulate static pages:

 RewriteEngine On
 RewriteRule /(img|download)/.* - [L]
 RewriteRule ^/(.+)/index\.html$ /?t=TOPIC&topic=$1       [PT]
 RewriteRule ^/(.+)/(.+)\.html$  /?t=STORY&topic=$1&id=$2 [PT]
 RewriteRule ^/(.+)/$            /?t=TOPIC&topic=$1       [PT]
 RewriteRule ^/rss\.xml$         /?t=RSS                  [PT]
 RewriteRule ^/sitemap\.xml$     /?t=SITEMAP              [PT]

Sharing code via email with git

In a clone of a remote repository, start a branch to hold your code:

 git-checkout -b my-changes

Do your work and commit changes as you like.

When you are happy with your work, create a temporary directory:

 mkdir /tmp/patches

Then change back to the master branch and build a set of patches from your branch with git-format-patch:

 git-checkout master
 git-format-patch -n -o /tmp/patches

A bunch of files, one per changeset, have been created in /tmp/patches. Now, use the git-send-email to send them, one per email, to the original author.

 git-send-email --no-thread --from me@here --to author@remote /tmp/patches

If author@remote acknowledges your changes, you can just merge your changes to the current master head and delete your temporary branch:

 git-merge my-changes
 git-branch -d my-changes

On the remote machine

If author@remote uses mutt, he can move to his working copy, call it and type |git-am on each message.

Matching git-svn strange authors to useful email addresses

Git-svn is a useful tool to communicate with a Subversion repository from git. You usually clone a repository with a command like:

 git-svn clone svn+ssh:// prj

And a prj directory is created with a full git repository. Then, you get another people changes with git-svn rebase and commit yours with git-svn dcommit.

It has one drawback, though; authors are mangled to something like

 Author: angel <angel@2e99d34b-3c1d-0410-9ca7-923d03b5684e>

which is not only ugly but completely useless.

To map this monstrosity to real user email addresses and names, use the following steps:

First, create the file ~/.gitusers with content like this:

 angel = Ángel Ortega <>
 otheruser = Other User <>

If you converted your SVN repository from CVS with something like cvs2svn you'll also find entries like this:

 Author: (no author) <(no author)@2e99d34b-3c1d-0410-9ca7-923d03b5684e>

Those ones can be converted with another line in ~/.gitusers.

 (no author) = Really Me <>

And now, instead of the usual git-svn clone command, use the following ones:

 mkdir prj
 cd prj
 git-svn init svn+ssh://
 git config svn.authorsfile ~/.gitusers
 git-svn fetch

Always maximized X11 terminal emulators

Add this to your ~/.bashrc:

[ -z "$DISPLAY" ] || wmctrl -r :ACTIVE: -b add,maximized_vert,maximized_horz

Desactivación de servicios telefónicos molestos

Telefónica (fijo)

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My preferred way of C code formatting

They mean: Kerninghan & Ritchie indentation, 4 spaces, no cuddled else, no tabs.

 indent -kr -i4 -nce -nut *.c

I previously used:

 indent -kr -i8 -nce *.c

Setting global git variables

 git config --global "Angel Ortega"
 git config --global

Building a point-to-point VPN (SSH tunnel) in one line

 pppd noauth \
     pty 'ssh root@REMOTE_HOST pppd notty noauth'

The remote host needs a passwordless authorized key.

Redirecting a full site to https

 <Location />
        RewriteEngine on
        RewriteRule ^/(.*)$ https://%{HTTP_HOST}/$1

Perl one-liner to know the length of an MP3 song

 perl -MMP3::Info -e '$i = get_mp3info($ARGV[0]); \
   printf "%d:%d", $i->{MM}, $i->{SS};' song.mp3