Combining ls and shuf ... ... and more

Introduction

Portuguese version

Some commands do not generate any output list, authough dealing with lists from other commands, the shuf command is one of these. If I want to get a random image name from my wallpapers dir I do:

ls -1A ~/img/backgrounds/* | shuf -n 1

The above command could be used to create a variable and be used as other command argument, in this particular case a command that, based on your wallpaper color, will set your terminal colorscheme:

sudo pip3 install pipx
pipx install pywal

The pipx command installs your python modules in a sandbox, avoiding namespaces clashes. After installing pywal you will have a wal command, using it I have created this shell script line:

/home/sergio/.local/bin/wal -i "$(ls -1A ~/img/backgrounds/* | shuf -n 1)"

Change the path and system variables accordingly, after that open up a new terminal and run the following command:

Update!

Watching more videos about pywal I have learned that you do not need to use the shuf command, just give a directory to the wal command and it will choose a random image from there, but the knowledge on using shuf will eventually

wal --preview

This way every time you run the command...

wal -i "path-of-your-wallpapers"

...you will see a preview of your terminal theme.

In the case of my "tiling window manager", the bspwm, I have a shortcut on my sxhkdrc:

# change background
super + b
    /home/sergio/.local/bin/wal -qi ~/img/backgrounds/ 

Also one line on my bspwmrc

/home/sergio/.local/bin/wal -qi ~/img/backgrounds/ 

Finally I have one line on my crontab that runs the same script every five minutes:

# crontab -e
# vim:et:sw=4:ts=4:cms=#%s:
# >/dev/null 2>&1   <- used to preven sending e-mail's
# env | grep -i display  to get your DISPLAY variable
# otherwhise feh will not be abble to change your background
# source: https://superuser.com/a/1122245/45032
DISPLAY=':0'
SHELL=/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin:/home/sergio/.dotfiles/algorithm/shell/bash/
XDG_PICTURES_DIR=/home/sergio/img
WALLPAPER_DIR=$XDG_PICTURES_DIR/backgrounds/
WAL=/home/sergio/.local/bin/wal
MAILTO=""
*/5    *    *    *    *  $WAL -qi $WALLPAPER_DIR
# */5    *    *    *    *  feh -z --bg-fill /home/sergio/img/backgrounds/*
# */5     *     *     *     *  wal -i "${XDG_PICTURES_DIR}/backgrounds/$(ls ${XDG_PICTURES_DIR}/backgrounds | shuf -n 1)"
#*/30    *    *    *    *  mpg123 /home/sergio/music/drink-water.mp3

Randomization in other apps:

Many utilities have their own flag for randomization, the mpg123 for example has a -Z flag for that.

For those apps that do not have randomization we can also use a shell trick ...

echo $((RANDOM % 10))

... Where 10 is the maximum randomized number possible