Vim, Bash, et. al.

This repository contains my personal configuration files. And some stuff too.

Programming tricks

Vim

General tips

• C-a C-x: When the cursor is on a number in normal mode, you can increment or decrement it by executing respectively

  CTRL-a
  CTRL-x

• xxd: You can read (and maybe edit?) binary files by using the shell's command xxd in a file by doing so:

  :%!xxd

  See also :help xxd

• character code and search/replace: Vim can display the code of the character under the cursor in normal mode. The command is ga. You can use the code then to search or replace some characters. Decimal code can be matched with \\%d..., hexadecimal with \\%x... and so on. All are listed in :help \\%d

• replace computed submatch: If you want to replace all the numbers on the line with half the value, you can run:

  :s;[0-9]\+;\=submatch(0)/2;g

• insert line number: To insert the line number at the beginning of the line:

  :s/^/\=line(\".\")/

Easter eggs

:help!
:help 42
:help holy-grail
:help |
:Ni!
:autocmd UserGettingBored * echo "Hello"
:help UserGettingBored
:set rightleft
:set revins

Shell, bash and SSH

• Variable operations:

  var="salut ca va bien"
  $var             = salut ca va bien
  ${var#*a}        = lut ca va bien
  ${var##*a}       =  bien
  ${var%a*}        = salut ca v
  ${var%%a*}       = s
  ${var/va/va pas} = salut ca va pas bien
  ${var/a/y}       = sylut ca va bien
  ${var//a/y}      = sylut cy vy bien

• Check if sudo:

  if (( $UID == 0 )); then

• Remove temporary sudo rights (if any):

  sudo -k

• redirect IO

  • Redirect STDOUT to file:

    echo "hello world" > file.txt

  • Redirect STDERR to file:

    echo "hello world" 2> file.txt

  • Redirect STDOUT and STDERR to file:

    echo "hello world" >& file.txt

  • Redirect STDOUT to STDERR:

    echo "hello world" 1>&2

  • Redirect STDERR to STDOUT:

    echo "hello world" 2>&1

• Numeric for loop (bash):

  for i in {1..10}; do

• Make special behaviour on exit (trap exit):

  function your_function_name() {
      ...
  }
  trap your_function_name EXIT

• command completion: Make a command suggests input (for instance .tex files):

  complete -f -X '!*.tex' your_command_name

Python

• assert calls can be disabled by calling python -O or python -OO (optimize flag)
• If you want to implement something which requires to be very performant, you can write it in fortran and use f2py to compile it into a python module.

LaTeX

A very good and complete reference is https://en.wikibooks.org/wiki/LaTeX

Installation

• texlive official source is recommended. Available sources in standard PPA are not recent enough...
• to update an official texlive installation, use the texlive manager (tlmgr): tlmgr update --self --all

Packages

Here are packages of interest. To get more information about a given package, use texdoc package_name or look at http://ctan.org

• lmodern and fontenc: these are required to make the text copiable from the PDF:

  \usepackage{lmodern}
  \usepackage[T1]{fontenc}

• babel: To have your text displayed according to the standards of the language you are writing in, you need:

  \usepackage[english]{babel}

• hyperref: this package allows you to make links inside and outside the document.

  • setup: once loaded you can set it up:

    \hypersetup{
      colorlinks        = true,
      bookmarks         = true,
      bookmarksnumbered = false,
      linkcolor         = black,
      urlcolor          = blue,
      citecolor         = blue,
      filecolor         = blue,
      hyperfigures      = true,
      breaklinks        = false,
      ps2pdf,\n";
      pdftitle          = {\ThisTitle},
      pdfsubject        = {\ThisTitle},
      pdfauthor         = {\ThisAuthors}
    }

  • commands: you can also use the following commands:

    \url{website link}
    \href{website link}{text to display}
    \href[reference in document]{text to display}
    \href{mailto:me@mail.com}{email me}

  • There also is a Form environment so users can fill in the PDF directly:

    \TextField
    \ChoiceMenu

• enumitem: if you want to get rid of the extra space in lists:

  \usepackage{enumitem}
  \setlist{noitemsep}

• tocbibind: To get the bibliography and the index numbered and in the TOC:

  \usepackage[section,numbib,nottoc,numindex]{tocbibind}

• fancyhdr: To set headers and footers, use the fancyhdr package. Using \fancypagestyle{plain} can help having the same page design everywhere (otherwise first page of chapters can be different).

• others useful packages:

  • listings: nice formatted code snippets
  • tikz: impressive schematics
  • draftwatermark: watermark background
  • ifthen: conditional behaviour
  • multicol: multicolumn in tables
  • lastpage: places a reference on last page
  • spreadtab: spreadsheet tables
  • colortbl: colored tables

document design

• frenchspacing: To remove the extra space after each sentence, use \frenchspacing

• margins: LaTeX default margins are huge! You can change them:

  \setlength{\topmargin}{-12.5mm}
  \setlength{\textheight}{250mm}
  \setlength{\hoffset}{-10mm}
  \setlength{\textwidth}{170mm}
  \setlength{\evensidemargin}{3.8mm}

• labelitemi: If you want to change the label of items (after the beginning of document!):

  \renewcommand*{\labelitemi}{\MyLabel}

  You can do the same for enumerate environment:\n";

  \renewcommand*{\labelenumi}{\arabic{enumi}.)}

• numberwithin: With big documents, you may want to have the numbered figures, tables, lists and so on numbered according to the chapter, section or whatever. You can use

  \numberwithin{equation}{subsection}
  \numberwithin{figure}{chapter}

• tocdepth, secnumdepth: You can choose to which depth sections must be numbered and included in the TOC:

  \setcounter{secnumdepth}{3}
  \setcounter{tocdepth}{2}

• graphicspath: If you have a lot of pictures to use and do not want to type the full path each time, you can use:

  \graphicspath

• today: To display the date of the typesetting according to the babel settings, there is the command \today. You may be interested in the package datetime2 (successor of datetime which is no longer supported).

• nocite: If you make a bibliography and want all the references to be displayed even if they were not quoted, you need \nocite{*}

Deeper insights

• starred newcommand: If you are concerned about typesetting performances, prefer to use the starred version of (re)newcommand when the content does not have any newline.

• jobname: You can use the command \jobname to have the name of the current file displayed.

• multiple same footnotes: In case you want to write a footnote and reuse it for multiple occurences, you can define the following commands:

  \newcommand{\FootnoteOne}[2]{\footnote{#2}\newcounter{#1}\setcounter{#1}{\value{footnote}} }
  \newcommand{\FootnoteRecall}[1]{\footnotemark[\value{#1}]}

• write package/class if not exists: If you need something in many files which is long and complicated to set up, you can write a package or a class. See the LaTeX wikibooks

Matlab

• set(0): If you like your graphs in a way that is not the default way, there is a trick. You can set some options which will be used for all graphs you will make. These can be set through the command set(0, 'property', 'value'); For instance, you can set the default color order for the plots, default font-size and style for axes, text, default marker size... To get the full list of properties available, simply run get(0)

• hsv: When doing plots with a variable number of lines, it may be helpful to use adaptable colors:

  colors = hsv(N);%% for N plots
  for i = 1:N
      plot(x{i}, y{i}, 'color', colors(i, :));
  end

  Personnaly I prefer to use hsv(N+2).

• enac tutorial: A good tutorial can be found on ENAC EPFL, especially the section about graphics.

Miscellaneous

• Emacs is a great operating system - it lacks a good editor, though.
• GoogleEarth flight simulator F-16: In GoogleEarth there is a flight simulator. You can change the paramter of the plane in the file $PATH_TO_GOOGLE/earth/free/resources/flightsim/aircraft/f16.acf Thrust can be changed with parameters P_max and F_max. Maximum values advised are respectively 60e9 and 20e6.