Shell and Scripting

A shell session can be either a login shell or a non-login shell.

A login shell is the first shell that runs under your user ID when you start an interactive session, such as logging in via tmux, SSH, or su -. This shell reads and executes the environment configuration files /etc/profile and ~/.bash_profile for bash. You can verify if a shell is a login shell by running shopt login_shell.

A non-login shell is any shell started in an existing session, like a terminal in a graphical environment, a shell inside tmux, or a shell within another shell. These shells do not read the environment configuration files (/etc/profile or ~/.bash_profile), but they do read the shell configuration file (~/.bashrc, /etc/bash.bashrc).

Default Shell

The default login shell for a user is configured in /etc/passwd. To check or change a user's default shell:

getent passwd mlibre
pritenv SHELL

Bash

Basics

Variables

my_var="Hello, World!"
echo $my_var

if

if [[ condition ]]; then
  # Code to execute if condition is true
fi

loops

for i in {1..5}; do
  echo "Iteration $i"
done

Functions

my_function() {
  echo "Hello from my function!"
}
my_function

Command Line Arguments

echo "First argument: $1"

Input and Output

read -p "Enter your name: " name
echo "Hello, $name!"

Metacharacters and Quoting

Command	Description
`*`	Matches zero or more characters. `ls /bin/zip*`
`?`	Matches single character. `ls file?.txt`
`[]` (square brackets)	Matches any one character within the range. `ls file[1-2].txt`
`{}` (curly braces)	expands values. `{a,b}.txt` expands to a.txt and b.txt
`'single quotes'`	Escape all metacharacters within string
`"double quotes"`	Interpret metacharacters within string

Execution methods

Command	Description	Execution Method
`./script`	Execute script in current directory as a new process	Shebang (`#!/`)
`sh ./script`	Run script with the default system shell (/bin/sh)	No Shebang (`#!/`)
`bash ./script`	Run script explicitly with the Bash shell	No Shebang (`#!/`)
`source ./script`	Execute script in the current shell, preserving changes	No Shebang (`#!/`)
`exec ./script`	Replace the current shell with the script (keeps PID)	Shebang (`#!/`)

Conditionals

Operator	Meaning	Example	Description
`-ne`	Not Equal	`$a -ne $b`	True if `$a` is not equal to `$b`
`-ge`	Greater than or Equal To	`$x -ge $y`	True if `$x` is greater than or equal to `$y`
`!=`	Not Equal (for strings)	`"$str1" != "$str2"`	True if `$str1` is not equal to `$str2`
`=`	Equal (for strings)	`"$str1" = "$str2"`	True if `$str1` is equal to `$str2`
`-lt`	Less Than	`$p -lt $q`	True if `$p` is less than `$q`
`-gt`	Greater Than	`$m -gt $n`	True if `$m` is greater than `$n`
`-le`	Less Than or Equal To	`$i -le $j`	True if `$i` is less than or equal to `$j`
`-f`	File Exists	`-f "$file"`	True if the file `$file` exists
`-s`	File is Not Empty (Size > 0)	`-s "$file"`	True if the file `$file` exists and is not empty
`-x`	File is Executable	`-x "$script"`	True if the script `$script` is executable

wait, ;, &&, ||, `, $#, $?, $()

Command	Description
`command1; command2`	Run 'command1' followed by 'command2'
`ls; pwd`	List files and then print the current directory
`mkdir myfolder; cd myfolder`	Create a folder and then navigate into it
command1 \|\| command2	Run 'command1', if it fails, run 'command2'
ls /nonexist \|\| echo "not found"	List a directory, and if it doesn't exist, display an error message
`command1 && command2`	Run 'command1', if it succeeds, run 'command2'
`git pull && npm install`	Pull from a Git and install Node.js packages if the pull is successful
`wait`	Pause execution until all background jobs are done
`sleep 10 & wait; echo "hi""`	Wait for background jobs to finish and then display a message
`command`	Executes `command` and returns its output as text
`$()`	Executes a command within parentheses and returns its output
`output=$(command)`	Executes `command` and stores its output in `output`
`$#`	Number of arguments passed to script
`$?`	Exit or return value of the last executed command (0 for success)
sleep `expr 5 \* 5`	Pause for 25 seconds (5 multiplied by 5)

echo, env, export, set, unset, variables

Commands	Description
`VAR_NAME=val`	Set `VAR_NAME` to `val`
`set`	displays shell variables and functions
`set -o`	Display current shell options
`set -e`	Exit immediately if a command in script exits with non-zero status
`unset MYVAR`	Unset the environment variable named `VAR_NAME`
`export VAR`	Make var available to child processes
`env`	View current environment vars
`echo $VAR`	Display value of `VAR`
`echo $PATH`	Display value of `PATH`
`echo $HOME`	Display user's home directory
`echo $EDITOR`	Display default text editor
`echo $HISTFILE`	Display command history file
`echo $USER`	Display current username
`echo $?`	Display last command exit status
`echo $PS1`	Display the shell prompt
`echo -e`	Enable interpretation of backslash escapes in the string
`echo -e "hi \n"`	Display "hi" with a newline character

Use export when you want to make a variable available to child processes Use set primarily for managing shell options and attributes, but it can also be used to set local variables

source, alias, type

Command	Description
`source`	Load functions into the current shell session
`source ~/.bashrc`	Reloads the user's Bash profile
`source my_script.sh`	Executes a shell script within the current shell
`alias`	Create or display command aliases
`alias ll='ls -l'`	Creates an alias 'll' for the 'ls -l' command
`alias c=clear`	Creates an alias 'c' for the 'clear' command
`unalias c`	Remove the alias 'c' for the 'clear' command
`type`	information about a command
`type ls`	output: ls is an alias for ls $LS_OPTIONS
`type ssh`	output: ssh is /usr/bin/ssh
`type source`	output: source is a shell builtin

history

Commands	Description
`history 5`	Displays the last 5 commands in the history
`!!`	Repeats the last executed command
`!*`	Represents all arguments of the last command
`!n`	Repeats the nth command in `history`
`!-n`	Repeats the nth command from the current command
`!string`	Repeats the most recent command that starts with `string`
`!:1`, `!:2`, ...	Represents the first, second, etc. arguments of the last command
`!:0`	Represents the command + arguments
`command !:0-2`	Executes the command with the first two arguments of the last command
`command !:1-2`	Executes the command with the second and third arguments of the last command
`command !:2*`	Executes command from the second arguments of the last command
`some !571:2*`	Executes some from the second arguments of 571st command in the history

Prompt Shell

echo $PS1

PS1='$(if [ $? -eq 0 ]; then echo -e "\[\033[42m\] \[\033[0m\]"; else echo -e "\[\033[41m\] \[\033[0m\]"; fi) \[\033[1;32m\]$(if [ $(jobs | wc -l) -gt 0 ]; then echo -n "\j "; fi)\[\033[1;36m\]\u\[\033[0m\] \[\033[1;33m\]\w\[\033[0m\] \[\033[1;34m\]$(if [ $(date +%H) -ge 6 -a $(date +%H) -lt 18 ]; then echo -n "☀️"; else echo -n "🌙"; fi)\[\033[0m\] '

# you may put your PS1 in .bashrc
nano .bashrc

Case-insensitive Auto completion

# Add the following line to the /etc/inputrc file to enable case-insensitive auto completion
echo 'set completion-ignore-case On' | sudo tee -a /etc/inputrc

# or as root
echo 'set completion-ignore-case On' >> /etc/inputrc 

# or for current user only
echo "set completion-ignore-case on" >> ~/.inputrc

Simple Bash Scripts

Mouse location

while true; do
  sleep 2
  xdotool getmouselocation
done

Get screen resolution

RES=$(xdpyinfo | grep dimensions | awk '{print $2}')
WIDTH=$(echo $RES | awk -Fx '{print $1}')
HEIGHT=$(echo $RES | awk -Fx '{print $2}')

Click, Move and scroll on the screen

#!/bin/bash

# Usage: ./click2.bash 3 30

# Check for two arguments
if [[ $# -ne 3 ]]; then
 echo "Usage: $0 <mouse idle time in seconds> <sleep time in each loop> <specific action each Nth time>"
 exit 1
fi

mousemoveAndClick() {
 # Move the mouse to the specified coordinates
 xdotool mousemove $1 $2
 # mouse click
 xdotool click 1
 # Sleep for 1 second
 sleep 1
}

scroll() {
 local direction=$1
 local count=$2
 if [[ $direction == "up" ]]; then
  for i in $(seq 1 $count); do
   xdotool click 4
   sleep 0.5
  done    
 elif [[ $direction == "down" ]]; then
  for i in $(seq 1 $count); do   
   xdotool click 5 
   sleep 0.5
  done
 fi
}

remove_esc() {
 # Move the mouse to the specified coordinates
 xdotool mousemove 1575 572
 # mouse click
 xdotool click 1
 # Sleep for 1 second
 sleep 1
}

press_esc_and_click() {
 # Press ESC
 xdotool key Escape
 sleep 1
 # mouse click
 xdotool click 1
 remove_esc
}



buy() {
 # Move the mouse to the specified coordinates
 xdotool mousemove 1556 1230
 # mouse click
 xdotool click 1
 # Sleep for 1 second
 sleep 1
}

counter=0
# Get the idle time in milliseconds
IDLE_TIME=$(echo "$1 * 1000" | bc)

while true; do
 # Get the current idle time of the mouse pointer in milliseconds
 IDLE=$(xprintidle)

 # Check if the mouse has been idle for at least the specified time
 if [[ $IDLE -ge $IDLE_TIME ]]; then
   
  ((counter++))
  echo "Increasing $counter"

  # Boss
  mousemoveAndClick 34 393
  press_esc_and_click
  
  # top left
  mousemoveAndClick 1173 647
  buy

  if [[ $((counter % $3)) -eq 0 ]]; then
   scroll "down" 40
  fi
 fi

 # Sleep for specified time
 sleep $2
done

And run:

chmod +x click.sh
./click.sh 1 30 50

zsh

sudo pacman -S zsh

Font

Monospace 12

Shell and Scripting

Login shell vs non-login-shell​

Default Shell​

Bash​

Basics​

Metacharacters and Quoting​

Execution methods​

Conditionals​

wait, ;, &&, ||, `, $#, $?, $()​

echo, env, export, set, unset, variables​

source, alias, type​

history​

Prompt Shell​

Case-insensitive Auto completion​

Simple Bash Scripts​

Mouse location​

Get screen resolution​

Click, Move and scroll on the screen​

zsh​

Font​

Login shell vs non-login-shell