Language Selection

English French German Italian Portuguese Spanish

MiniTutor: Shell Colors and Cursor Positions

Filed under
Linux

You can use characters to modify texts and how they are displayed, and also for fun you can draw, create animations, statusbar, progressbar and more.

These commands can be called as escape sequencies because all they use ASCII's ESC (033). They must be send directly to the terminal and you can use 'print', 'printf' or 'echo'. The sequencies use ESC to definy colors and cursos position, they begin with an 'ESC' followed by a '[', and close with a 'm'. In the middle we must add numbers separeted by ';'.

First, we show how to use these commands and sequencies to change default colors displayed by shell. The command format is 'ESC[n1;n2;...m', it means, after the begin '033[' (ESC[) and before the end 'm', we have all numeric instructions. The default is '0' if any number are written, and those numbers indicate text color, background color and video atributes or codes. Those atributes can change text form and how the colors is going to be showed.

The list of text colors is: 30 (black/gray), 31 (red), 32 (green), 33 (brown/yellow), 34 (blue), 35 (purple), 36 (cyan) and 37 (gray/white). The list of background colors is: 40 (black/gray), 41 (red), 42 (green), 43 (brown/yellow), 44 (blue), 45 (purple), 46 (cyan) and 47 (gray/white). The atributes are: 0 (default), 1 (bold), 5 (blinking) and 7 (reverse background and color). There are some differences between colors above as you can see, for example 43 is used to display a brown color, but if you enable bold text the color turnes to yellow.

The number are read following this sequence: background, text color and atributes, for example '40,32,1,5' means black background, green color, bold text and blinking.

You must not forget to enable interpretation of backslash escapes, '-e' option, while using 'echo, for example: echo -e '\033[41m TESTING \033[m'.

Test example: echo -e '\033[40;33;1m Welcome to \033[40;31;1m GoblinX\033[40;33;1mNewsletter \033[m'.

Second, after learn how to change colors, we show how to change the text position. The command to set where display a text is 'ESC[. The common list is: ESC[nA (n lines up and same column), ESC[nB (n lines down, same column), ESC[nC (n columns to the right, same line), ESC[nD (n columns to the left, same line), ESC[nE (n lines down in column 1), ESC[nF (n lines up, column 1), ESC[nG (go to n column, current line) and ESC[n;mH (go to column m and line n).

An example: echo -e '\033c\033[4;7HSaturday\033[AMonday\033[2B\033[DWednesday'

In the above line, '\033c' cleans the screen, '\033[4;7HSaturday' writes Saturday at line 4 column 7, '\033[AMonday' moves the cursos up one line and writes Monday, '\033[2B' moves the cursor two lines down in the same column, and '\033[DWednesday' goes back one column in the same line and writes Wednesday.

There are also more commands to move the cursor before write a text and also others to clear texts and move the screen. The list is: ESC[nJ (n=0, clear until the end of the screen, n=1, clear until the begin of the screen, n=2, clear all screen) ESC[nK (n=0, clear until the end of the line, n=1, clear until the begin of the line, n=2, clear all line), ESC[nM (clear n lines below), ESC[nP (clear n characters in the right side), ESC[nX (clear n characters in the left side and write spaces instead), ESC[n@ (insert n blank spaces), ESC[nL (insert n blank lines), ESC[nS (move the screen n linhas up) and ESC[nT (move the screen n linhas down).

Test example: echo -e '\033c \033[40;33;1m Welcome to \033[4;7H \033[40;31;1m GoblinX\033[1C \033[40;33;1mNewsletter \033[m'

Another example, a counter:
for i in 1 2 3 4 5 6 7 8 9; do echo -ne "\033c \033[G\033[@Counted =\033[11G\033[0K$i"; sleep 1; done; echo

Your shell scripts can inform and also be funny, you just need to let your imagination flyes. This minitutor is heavly inspired by an article in the book 'Programação Shell Linux' written by Julio Cesar Neves.

Minitutor from: GoblinX Minitutors

More in Tux Machines

Slackware Live Edition – on its way to 1.0?

Last week the second Beta of the upcoming Slackware 14.2 was released. My goal was to have a new Beta of my liveslak ready by that time, so that I could provide new ISO images to test the Slackware Beta2 on a live medium. Unfortunately, there was an attack of the flu in my team at work and things got a bit busier than usual. There was a plus side to this: some last moment bug fixes which could be applied to my scripts – the result of having more evenings available to test. Therefore the new release is not labeled “0.5.0” but “0.5.1” Read more

Leftovers: KDE

  • Cantor migrating to Phabricator: which tools our contributors must to use
    Projects and software developed by KDE community are going to migrate for a new tool to manage our code, commits, reviews, tasks, and more. This tool is Phabricator and you can visit the instance for KDE projects in this address. Since November 2015 we are migrating Cantor to Phabricator. After our first successful review code some days ago, I decided to write a post about which tools our contributors must to use while the migration process is not finished.
  • Kdenlive's sprint report
    Last week-end, Vincent and me met in Lausanne for a Kdenlive sprint. One of our goal was to merge Gurjot Singh Bhatti's GSoC work on curves for keyframes. This was more work than expected and we spent many hours trying fix the curves and make keyframes behave correctly. Not much time was left for sleep, but we still managed to get outside to make a group (!) picture in the woods above Lausanne.
  • Jekyll 3.x
    I’ve found three different types of transition issues (it is cool to look at these in a project I do not upgrade on a daily basis like Plasma and the rest of the KDE software).
  • kdev-python on Windows: try it!
    I spent the last two or three days playing around with KDE on Windows, with the aim of getting my Python language plugin for KDevelop to run there. In the end, it wasn’t that hard to get this to work — not as hard as I would have expected it to be, anyways.

Manjaro ARM launched

Hi community, wonderful news in regard of architecture expanding within Manjaro Linux. It all started with a simple post on our developers mailing list. Somebody wants to do Manjaro for ARM … Just after one month of development our first alpha release is now ready. So what is this all about? Manjaro Arm is a project aimed to bring you the simplicity and customability that is Manjaro to ARM devices. These devices are growing in numbers and can be used for any number of applications. Most famous is the Raspberry Pi series and BeagleBoard series. Read more

Plasma 5.5.4 and Calligra Suite 2.9.11 now available

The 4th update for KDE's Plasma 5.5.x series is now available to all Chakra users. According to the release schedule, unless new issues occur, this will be the last update for this series before 5.6 gets released next month. Plasma 5.5.4 as usually includes a month's translations and bugfixes, with the authors highlighting the improvements for handling multi-screen setups. The Calligra Suite also receives a bugfix update to version 2.9.11, which mainly provides fixes for krita and kexi. Read more