First off,

:map
...
...
<Esc>OM       <CR>
<Esc>Ol       ,
<Esc>Ok       +
<Esc>Om       -
<Esc>Oj       *
<Esc>Oo       :
<F2>          :sp ~/TODO<CR>Go* <Esc><Up><Right><CR>
<xHome>       <Home>
<xEnd>        <End>
<S-xF4>       <S-F4>
<S-xF3>       <S-F3>
<S-xF2>       <S-F2>
<S-xF1>       <S-F1>
<xF4>         <F4>
<xF3>         <F3>

shows a list of available maps

Let us start with a small example:

:map <F2> :r!ls ~/<CR>

As you can see, maps are created very much like abbreviations.
When you type F2, Vim executes the associated sequence for that key. It is important to use <CR> when you are using :commands. Otherwise, you will have to type ENTER yourself. The map above reads the content of the ls ~/ command, i.e. it lists the $HOME directory.

When you work with maps, you are not limited to commands. You can tell Vim to “simulate” certain keystrokes. For example, you might want to execute something like “After this, I would like to move the cursor to the left”. This can be done with the “<>” notation (:help <> for more information). The following map illustrates this concept:

:map <F2> ifor(;;) {<CR>}<Up><Right><Right><Right>

Now, when pressing F2, the following text is inserted (the underscore represents the position of the cursor):

for(_;;) {
}

Notice you are still in insert mode. We could have achieved something similar with the following map:

:map <F2> ifor(;;) {<CR>}<ESC>kf;i

I personally prefer the latter. In my opinion, working in command mode is cleaner.

The following map is quite useful:

:map <F4> I#include <<ESC>A>

Let us analyze what that sequence does. First, it goes into command mode and places the cursor at the beginning of the line in insert mode. Then, it inserts the “#include <” string. Finally, it adds “>” at the end of the line.

Assuming you have a text like the following:

stdio.h

Placing the cursor on that line (at any column) and pressing F4 rewrites the line as follows:

#include <stdio.h>

Maps can deal with buffers, windows, tabs (from Vim 7 onwards) and such. Here is a small example. Suppose you have a TODO file in your $HOME directory. From time to time, while you are working, you want to add a new entry. Sounds reasonable, right?. Imagine we have a TODO file that looks like this:

* Stuff
* Things

We could easily open the file and make it ready to write a new entry with a simple map:

:map <F2> :sp ~/TODO<CR>Go* <Esc>a

Let us explain what is going on here: We split the window horizontally, editing the TODO file at the same time (:sp ~/TODO). Then the cursor is placed at the end of the file. We open a new empty line and write a “* ” (Go* ). Finally, we leave the cursor in insert mode. This way we just have to type the thing we want to remember and then we can :close the top window.

Another simple example:

:map <F6> :w %.bakcup

This saves the current buffer with the same name plus the “.backup” extension. The % is a special variable which contains the name of the current file.

Finally, if you want to delete a map because it is no longer useful, you can :unmap it.

Conclusion
Maps are a very powerful tool. You can do almost anything you may need, no matter how complex it is. There are a lot of interesting macros on the Internet. I recommend you to search the web!

VIM SHEET (VIII)

• map Map a key to a set of commands / List available maps
• unmap Unmap key

It started with the goal of secure storage of the shadow file and, in general, of any database of secret authentication tokens (think of passwords -actually hashes of passwords- of users of a Web-based service, for example). We consider it addresses the main concern on those databases: dictionary attacks and rainbow tables, which have become available at negligible cost: there is a cloud-based service for doing dictionary attacks on a WPA key.

Our approach for storing shadow files is to use a separate server for checking the correctness of the password introduced by the user, taking advantage of asymmetric key encryption.

Instead of keeping the hash (as crypt(3) does, or SHA1) of the password in the shadow file, we store an OAEP RSA-cyphertext of the hashed password (using a public encryption key) and, each time the user tries to log in, ask via TCP someone (the owner of the private key) if another OAEP-encryption of the hash of the password issued by the logging user matches the stored token. That is: use an”oracle” to check if the user has entered the correct password or not. This “oracle”, which is a standalone machine, is the Sibyl and the device we use to implement it is a Bifferboard.

The details are on the web of the Sibyl project. We hope you like it and use it.

As we saw in previous posts, Vim is the perfect tool if you want to save time in your daily work. It helps you in the write-compile-debug cycle, it indents and autoindents code, it is extremely powerful for searching, replacing and many other frequent tasks.

In this post I will introduce an interesting feature meant to make you type less: abbreviations.

Abbreviations are, as their name indicates, a way to create an association between a short set of characters and a piece of text (or a command).

Abbreviations can be used in insert, replace or command mode. The keywords used to work with abbreviations are all the same, but adding a proper prefix if necessary (i for insert mode, c for command mode and ! for both).

iab        Create abbreviation for theinsert mode
cab        Create abbreviation for the command mode

Recently, I had to write a dockbook template using perl and the Mason library and found myself typing continuously the following thing:

$data->[0]->{}

and between the curly braces the hash key. After writing that twice I got bored of doing it (yep, I am a lazy guy) so I created the following abbreviation:

iab dh $data->[0]->{!cursor!}:call search('!cursor!', 'b')cf!

It associates the “dh” characters with the $data->[0]->{!cursor!}:call search(‘!cursor!’, ‘b’)cf! string. This string writes “$data->[0]->{}” and places the cursor between the curly braces (do not worry about the “call search” stuff, the example could have been iab dh $data->[0]->{} ) By the way, abbreviations are not recursive, so you will never end up stuck in an infinite loop.

Since writing a tag-like document is a real pain, I decided to abbreviate some of the common tags I was using the most, so I created the following abbreviations:

iab fp <formalpara><CR><LF></formalpara>
iab p <para></para>
iab il <itemizedlist><CR><LF></itemizedlist>
iab li <listitem></listitem>
iab e <entry><CR><LF></entry>
iab t <title></title>
iab it <informaltable><CR><LF></informaltable>
iab r <row><CR><LF></row>

<CR> and <LF> have the common meanings (Carriage Return and Line Feed respectively). They were very convenient. You can copy them to your .vimrc file.

But what if you do not want an abbreviation to be expanded?

Suppose we have the following abbreviation:

iab to Total

and we want to write the following sentence:

"I went to Paris"

As soon as you type the space after “to”, the abbreviation will be expanded and you will end up with:

"I went Total "

To avoid this problem, press Ctrl-V after the problematic abbreviation and then continue typing normally.

To disable an abbreviation permanently you can use “unabbreviate”. For instance:

:unabbreviate dh

“abbreviate” lists the current abbreviations. E.g:

i  t             Total
i  b             back

The first column shows the mode in which the abbreviate is available, the second shows the abbreviation and the third one the text it expands to.

Abbreviations are a convenient way of saving some (or possibly a lot of) work, specially if it is repetitive.

Vim Sheet(VII)

• [i/c/!]ab Create an abbreviation in the specified mode
• unabbreviate Deletes an abbreviation
• abbreviate List available abbreviations

$pkg_info -W /usr/local/bin/mysql
/usr/local/bin/mysql was installed by package mysql-client-5.5.2

Enjoy!

The following C code does the trick: (first of all we must set t to 0);

int k = (L%2 ? L/2+1 : L/2);
memset(t, 0, L/2);
for(i=0; i<L; i++){
  t[i/2] += ((i%2) ? 1 : 16) *
    ((f[i] > 'F') ? (f[i] - 'a' + 10) :
      ((f[i] > '9') ? (f[i] - 'A' + 10) :
        (f[i] - '0')))
}

Thus, if f points to the string 100aff, t points to the sequence of bytes 16, 10, 255 after the loop.

The reverse operation is well known:

for(i=0; i<k; i++){
  sprintf(f+2*i, "%02X", t[i]);
}

I just don’t want to forget it.

$ echo '$1$CSmo96nX$G0PL/Cs/of5qDN2vMnyHp0' | openssl base64 | tr -d '\n'

You should always use the -n option if you want to make sure there is no spurious trailing newline:

$ echo -n '$1$CSmo96nX$G0PL/Cs/of5qDN2vMnyHp0' | openssl base64 | tr -d '\n'

(By the way, the encrypted message says just 'patata0' and it is not my password).

Or… is it?

Tested on two Linux systems (Fedora & Ubuntu) and one Snow Leopard.

(setq-default TeX-master "00father.ltx")

because most of the time I am editing multifile projects.

However, from time to time I need to write a single-file document and in this case, naming it 00father.ltx is not that useful, and I do not want to have to set the master-file variable each time I load the file.

There is an easy way to get this done. Just include a line at the top of the file -as a comment in the appropriate language- setting the variables. The syntax is as follows (in C, for example):

/* -*- variable1: value1; variable2: value2; -*- */

I am giving two examples. The first one in C again. Assume this is the header of a file called trial.c

/* *-* tab-width: 8; column-number-mode: 1; fill-column: 80; -*- */

The line tells emacs to set the length of a tab to 8 spaces (usual in BSD), to show the column number in the information line and to wrap lines (if wrapping -fill-mode- is set) at 80 characters.

For my LaTeX issue, the first line of a single-file document letter_to_my_friend.ltx goes as follows (notice the difference in the comment syntax):

% -*- TeX-master: "letter_to_my_friend.ltx"; -*-

I have checked and if your file is a shell script, which usually begins with

#!/bin/sh

(or some similar line), you can place the variable-setting line just afterwards.

• Merge the previous version
• Commit

Like this (assumming you want to roll back from version 61 to 58):

pera $ svn merge r61:58 https://my.project.at.sourceforge/svnroot/project/dir1/src/
[... output ...]
pera $ svn ci -m "Reverted to version 58"

which is strange but works. Forget about the revert command, it has a different functionality.
You may want to run

pera $ svn merge --dry-run r61:58 ........

to check the changes which will take place before messing everything up.

$ ipcs -s

------ Semaphore Arrays --------
key        semid      owner      perms      nsems
0xdd3adabd 0          fernape    600        1         

I had forgotten about this command but I remembered it when we ran out of semaphores in our Linux system two days ago.

Other way of getting the same information is to cat the following files:

$ ls /proc/sysvipc
msg        sem        shm

Enjoy!

#!/bin/bash

usage() {
  name=`basename $0`
  echo "Usage: $name hh:mm:ss"
  echo "Example: $name \"00:15:30\""
}

if [ $# != 1 ]
then
  usage
  exit
fi

IFS=:
set -- $*
secs=$(( ${1#0} * 3600 + ${2#0} * 60 + ${3#0} ))
while [ $secs -gt 0 ]
do
  sleep 1 &
  printf "\r%02d:%02d:%02d" $((secs/3600)) $(((secs/60)%60)) $((secs%60))
  secs=$(( $secs - 1 ))
  wait
done
echo

It works in any POSIX shell.

I was writing one but I found this thread of the UNIX and linux forum where the user cfajohnson solves it in a better way.

The code:

sleep 1 &
...
wait

minimizes the skew of the loop, so every cycle is as close to 1 second as possible.

I have not included the final beep in the script. You can do it with the usual:

printf ("\a")

which works on all unix-like systems.

In linux you can use the beep command that allows you to control pitch, duration, and repetitions, for example:

$ beep -f 300.7 -r 2 -d 100 -l 400

makes 2 repetitions of a beep at 300.7 Hz for 400 milliseconds and a delay between repetitions of 100 milliseconds.

In OS X you can play with the say command:

$ say "You deserve some rest"