Screensavers From and Within the Linux Terminal CLI

1. Introduction

The original purpose of screensavers is, as the name implies, screen preservation. In the age of displays with a cathode ray tube (CRT) or crystals, phosphorus, and other elements could literally get burnt in on the screen after a long time of showing the same image. Although this is for the most part an artifact of the past, organic light-emitting diode (OLED) displays are susceptible to the same issues. In any case, the term and general idea of screensavers have remained mostly for enjoyment.

In this tutorial, we check out different options for running a screensaver from and within the terminal. First, we look at triggering the graphical screensaver from the command line interface (CLI). Next, we check how to set up a terminal screensaver to run when the user is idle. After that, we explore one of the main terminal user interface (TUI) graphics libraries. Finally, we go through specific text-based screensaver implementations.

In all cases, we use apt as the package manager.

We tested the code in this tutorial on Debian 12 (Bookworm) with GNU Bash 5.2.15. It should work in most POSIX-compliant environments unless otherwise specified.

2. Run Graphical User Interface (GUI) Screensaver From Terminal

Indeed, we can save, turn off, and lock our screen from the terminal in different ways.

2.1. Stop Screen

To begin with, we can use the basic xset:

$ xset dpms force off

In particular, we force the display power management signaling (DPMS) to turn off the screen.

Alternatively, we can use xrandr:

$ xrandr --output DVI1 --off

In this case, we turn –off the –output named <NAME>.

Both of these options rely on DPMS and are part of the Xorg server.

2.2. X Screensaver

If using X11, we can employ xscreensaver to trigger the screensaver:

$ apt-get install xscreensaver

After installing the xscreensaver package, we run xscreensaver-command:

$ xscreensaver-command -lock -activate

In particular, we -activate the -lock screen. Although X is at the core of many desktop environments, this isn’t a universal solution.

2.3. GNOME

Next, we check gnome-screensaver for GNOME:

$ apt-get install gnome-screensaver

After installing the package, we use the command of the same name:

$ gnome-screensaver

At this point, if we run the classic GNOME interface, we should see the current screensaver and lock screen.

2.4. KDE

Finally, let’s see a native alternative for KDE:

$ qdbus org.freedesktop.ScreenSaver /ScreenSaver Lock

In this case, we use the QT control command qdbus.

2.5. Universal Control

Similarly, we can use xdg-screensaver in many modern settings:

$ apt-get install xdg-screensaver

Now, we employ xdg-screensaver with activate:

$ xdg-screensaver activate

Since XDG is a widely adopted standard, this option runs on a very low level and should apply to many desktop environments.

3. Run Command Line Interface (CLI) Screensaver in Terminal

Naturally, CLI-based screensavers are usually a more exotic and rare breed. Because of this and the mostly text-based Linux experience, here, we mainly focus on such screensavers.

In practice, we can set up text-based screensavers to start automatically. One of the best, simplest, and most flexible ways to do so is with the use of terminal multiplexers, but we can use more native tools as well.

3.1. Native Shell

To begin with, we can come up with a basic timeout-like background script in Bash that finds all open shells and runs a screensaver command in each:

$ cat screensaver.sh
#!/usr/bin/env bash

# get current shells
shells=$(cat /etc/shells | grep '^/' | grep -v tmux)

# shell processes array
shellpids=()

# for each shell, add PID to shell processes
for shell in $shells; do
  shellpids+=($(pidof $shell))
done

# leave only unique values
shellpids=($(for shellpid in "${shellpids[@]}"; do echo "${shellpid}"; done | sort -u))

# run the screensaver for each shell
for shellpid in "${shellpids[@]}"; do
  gdb -p $shellpid -batch-silent -ex 'p system("/path/to/screensaver")' 2>/dev/null
done

Here, we get all current shells from /etc/shells via cat, ensuring we only have uncommented lines with full paths and exclude any terminal multiplexer shells. After that, we use pidof on each shell and store the results in the shellpids array. Next, we ensure the shellpids array only contains [-u]nique values via the sort command. Finally, we use gdb for each [-p]rocess ID (PID), thus silently running our screensaver for each shell.

Of course, we replace /path/to/screensaver with our desired command. Naturally, running the script automatically should be done via a scheduler like cron. This can become tedious and dangerous.

Instead, let’s employ environments that can have scripts running in the background.

3.2. screen

Another example of running a script automatically is the screen multiplexer command, which has screensaver capabilities built-in.

First, we modify our $HOME/.screenrc file:

$ cat $HOME/.screenrc
blankerprg /path/to/screensaver
idle 60 blanker

In this case, we first define our screensaver command via the blankerprg command. After that, we set the idle time before activating it to 60 seconds.

At this point, screen sessions that idle for a minute run /path/to/screensaver.

3.3. tmux

Of course, the ubiquitous tmux, due to its ability to run background commands, also supports different ways to activate a screensaver. To work with them, we modify the $HOME/.tmux.conf file.

First, we can just ensure the monitor turns off after a given time:

$ cat $HOME/.tmux.conf
set -g monitor-silence 60
set -g silence-action current
set -g visual-silence off
set -g alert-silence clock

Initially, we start monitoring for 60 seconds of silence with monitor-silence. Next, silence-action sets only the current window as the target of the silence monitoring. After that, we prevent any visual-silence notifications. lastly, we configure the built-in clock to run after the set amount of silence.

Since clock might not be the best way to save a screen, let’s use our own instead:

$ cat $HOME/.tmux.conf
set -g lock-command "/path/to/screensaver"
set -g lock-after-time 60
set -g visual-bell off

Similar to screen, we first set the lock-command and then the idle time before a lock event. Importantly, we might need to turn off the visual-bell, as it can prevent the screensaver from running.

Now, let’s see a common library that facilitates text-based screensavers.

4. ncurses

The ubiquitous ncurses library and application programming interface (API) enables terminal user interface (TUI) creation in a fairly platform-independent manner. It handles several aspects of the interface build in different ways:

provide high-level abstractions
handle low-level functions
optimize screen changes

The name Ncurses means new curses as this is the next iteration of another, similar, project called curses mainly available on BSD platforms.

Importantly, although ncurses is part of GNU, it has another license, which sometimes renders it incompatible with projects.

4.1. Install ncurses

On Debian-based platforms, we can install Ncurses via its apt packages:

$ apt-get install libncurses5-dev libncursesw5-dev

Alternatively, we use yum or dnf with the ncurses-devel release on RPM Linux distributions:

$ dnf install ncurses-devel

At this point, we should have the library available for use:

$ ldconfig -p | grep ncurses
        libncursesw.so.6 (libc6,x86-64) => /lib/x86_64-linux-gnu/libncursesw.so.6
        libncurses.so.6 (libc6,x86-64) => /lib/x86_64-linux-gnu/libncurses.so.6

Here, we use ldconfig to verify the library installation and see if it’s available.

4.2. Ncurses Text Positioning

To begin with, let’s see a basic custom function:

$ cat ncurses-center.c
#include <ncurses.h>
#include <string.h>
#include <stdlib.h>

void print_at_center(WINDOW *win, char *string)
{
  int length, x, y;
  int height, width;
  float xmiddle, ymiddle;

  // if no win was passed, use the standard screen
  if(win == NULL) { win = stdscr; }

  // get screen dimensions
  getmaxyx(win, height, width);

  // get text length (effectively width)
  length = strlen(string);

  // calculate middle based on text length and number of lines (1)
  xmiddle = (width - length) / 2;
  ymiddle = (height - 1) / 2;

  // use calculated values as coordinates
  x = (int)xmiddle;
  y = (int)ymiddle;
  mvwprintw(win, y, x, "%s", string);

  // apply changes
  refresh();
}
[...]

In this first part of ncurses-center.c, we see our custom function print_at_center(), which takes an Ncurses window handle and a string as arguments. Then, it gets the screen dimensions and calculates where the text should be based on its length.

Of course, to use these functions, we should initialize Ncurses.

4.3. Ncurses Initialization and Colorization

The second part of ncurses-center.c is a main() function, which initializes Ncurses and colorizes any future text output:

$ cat ncurses-center.c
[...]
int main(int argc, char *argv[])
{
  // initialize ncurses mode
  initscr();

  // check for color support
  if(has_colors() == FALSE) {
    endwin();
    printf("No color support in terminal.\n");
    exit(1);
  }

  // start color mode
  start_color();
  // set color pair 1 to red and black
  init_pair(1, COLOR_RED, COLOR_BLACK);
  // set current color pair to 1
  attron(COLOR_PAIR(1));
  // print at the center of the [st]an[d]ard [scr]een
  print_at_center(stdscr, "Colorful text at the center.");
  // unset current color pair
  attroff(COLOR_PAIR(1));

  // allow time to view the results by expecting a single [ch]ar
  getch();

  // destroy ncurses window
  endwin();
}

Finally, main() disables colorization, awaits confirmation of the output and uninitializes Ncurses.

In this self-explanatory code snippet, we use the ncurses.h file to have access to the Ncurses interface.

4.4. ncurses Functions

Let’s clarify some of the Ncurses-specific code:

initscr(): start ncurses mode
has_colors(): check terminal color support
start_color(): enable color usage
init_pair(): define a color pair
attron(): enable attributes
attroff(): disable attributes
getch(): away a single character input
endwin(): conclude Ncurses usage
getmaxyx(): get screen dimensions
mvwprintw(): print formatted output (similar to printf())
refresh(): refresh from the buffer

In essence, we perform several steps:

initialize ncurses
start color mode after ensuring the terminal supports it
create a color pair and set it as the current
print the text at the center
wait until a key is pressed
exit ncurses

This example shows the basics of ncurses usage.

4.5. Verify ncurses Installation

To confirm, we can build and link code with gcc:

$ gcc ncurses-center.c -o ncurses-center -lncurses

Now, we can run it:

$ ./ncurses-center

Finally, let’s see the result:

The simple output is a red string at the center of the terminal.

5. Terminal Text-based Screensavers

At this point, we can go over some examples of text-only screensavers for the CLI environment.

5.1. cmatrix

The classic cmatrix program is a screensaver that imitates the visuals of a terminal from a famous movie: falling letters in green.

On the one hand, we can use make to compile cmatrix from source after cloning or downloading the official repository:

$ git clone https://github.com/abishekvashok/cmatrix.git
$ cd cmatrix
$ ./configure && make && make install

This should work as long as we have ncurses installed since that’s the main dependency.

However, cmatrix also comes as a package available for different platforms:

$ apt-get install cmatrix

Either way, at this point, we should be able to try out the screensaver:

Visibly, the result looks like the movie it attempts to emulate. Moreover, we can augment the screensaver behavior with many options such as [-a]synchronous scrolling, [-b]old characters, specia[-l] fonts, and others.

The final result is also interactive, so we can toggle some of these options at runtime.

5.2. pipes.sh

Another classic screensaver is the 2D pipes.sh animation, which shows snake-like lines in different colors going around the screen.

The pipes.sh script only depends on Bash and terminal formatting via ncurses.

So, let’s download it via wget and make sure it’s executable via chmod:

$ wget https://raw.githubusercontent.com/pipeseroni/pipes.sh/master/pipes.sh
$ chmod +x pipes.sh

Of course, we can clone the repository via git and install the script as well:

$ git clone https://github.com/pipeseroni/pipes.sh.git
$ cd pipes.sh
$ make install

Either way, at this point, we should be able to run the script:

$ ./pipes.sh

Let’s see the result:

Again, we can set options such as the pipe [-t]ype, [-f]ramerate, [-r]eset count, and [-s]traight line probability

5.3. Termsaver

The Termsaver package includes many different animations and utilities as screensavers in the terminal:

urlfetcher: URL contents, typing animation
starwars: Star Wars ACII animation
matrix: Matrix movie terminal animation
jokes4all: recent jokes from jokes4all.net (NSFW)
clock: digital clock
programmer: source code, typing animation
quotes4all: recent quotes from quotes4all.net
rssfeed: RSS feed information
rfc: random RFC contents
sysmon: graphical system monitor
randtxt: text in random places on screen
asciiartfarts: ASCII images from asciiartfarts.com (NSFW)

Since it’s based on Python, the termsaver package can be installed via pip:

$ pip install termsaver

Alternatively, we can download, compile, and install:

$ tar -zxvf termsaver-{version}.tar.gz
$ cd termsaver-*
$ python -m build
$ cd dist/
$ pip install termsaver-*-py3-none-any.whl

At this point, we should be able to now see how termsaver matrix holds up against cmatrix, as well as use termsaver-specific implementations.

One big star of termsaver is the starwars movie:

$ termsaver starwars
[...]

        ..........       @@@@@    @@@@@   ..........
         .........      @     @  @     @   .........
         .........         @@@   @     @    ........
          .......        @@      @     @     .......
           .....        @@@@@@@   @@@@@  th   .......
           .....      -----------------------  ......
            ...         C  E  N  T  U  R  Y      .....
            ..        -----------------------     ....
            ..        @@@@@ @@@@@ @   @ @@@@@       ...
            ==          @   @      @ @    @          ==
          __||__        @   @@@@    @     @        __||__
         |      |       @   @      @ @    @       |      |
_________|______|_____  @   @@@@@ @   @   @  _____|______|_________

Let’s also check the sysmon utility that shows resource usage:

Unlike other screensavers, diversity comes from the choices instead of the configuration options.

5.4. ASCIIquarium

A fairly old but very impressive terminal screensaver is the asciiquarium by RoboBunny, a fish-and-water-themed animation.

First, we install the dependencies, which require Perl and cpan:

$ cpan install Curses && cpan install Term::Animation

Once done, we can download the ASCIIquarium package and install it:

$ wget http://www.robobunny.com/projects/asciiquarium/asciiquarium.tar.gz
$ tar -zxvf asciiquarium.tar.gz
$ cd asciiquarium*
$ cp asciiquarium /usr/local/bin
$ chmod 0755 /usr/local/bin/asciiquarium

At this point, we can check the graphics:

$ asciiquarium

Let’s see the result:

With a lot of randomly generated elements, colors, and objects, this is one of the most diverse screensavers on our list.

5.5. ASCII Saver

The ASCII Saver is a screensaver picker based on a flexible Python VT100 animation player, which can reproduce any .vt file. In short, VT100 is a format for storing text-based animations.

To install, we clone the repository and use make:

$ git clone https://gitlab.com/mezantrop/ascsaver.git
$ cd ascsaver
$ make && make install clean

At this point, we can run ascsaver with a given [-f]ile:

$ ascsaver -f /usr/local/share/ascsaver.art/globe.vt -p 0

Let’s see the result:

Finally, we can choose from a vast array of VT100 animation files to use with ascsaver.

6. Summary

In this article, we talked about screensaver control and play in the terminal.

In conclusion, although screensavers are usually associated with graphics, the Linux CLI doesn’t give way with its diverse choices.

Full Archive

About Baeldung

Administration

Filesystems

Processes

Files

Scripting

Installation

Networking

Security

1. Introduction

2. Run Graphical User Interface (GUI) Screensaver From Terminal

2.1. Stop Screen

2.2. X Screensaver

2.3. GNOME

2.4. KDE

2.5. Universal Control

3. Run Command Line Interface (CLI) Screensaver in Terminal

3.1. Native Shell

3.2. screen

3.3. tmux

4. ncurses

4.1. Install ncurses

4.2. Ncurses Text Positioning

4.3. Ncurses Initialization and Colorization

4.4. ncurses Functions

4.5. Verify ncurses Installation

5. Terminal Text-based Screensavers

5.1. cmatrix

5.2. pipes.sh

5.3. Termsaver

5.4. ASCIIquarium

5.5. ASCII Saver

6. Summary