Master Bash Scripting: Variables, Loops, Functions, and More

Bash Scripting Overview

Bash scripts allow you to automate a wide range of tasks on Unix-like operating systems without installing additional dependencies. They are portable, lightweight, and essential for developers working with command‑line environments.

Variables

Bash variables are case‑sensitive and are assigned using the = operator without spaces. To reference a variable, prepend $.

STATE=LinuxMi

STATE="Ubuntu Linux"

echo $STATE

Printing Values

You can output text with echo for simple messages or printf for formatted strings. Example:

STATE=LinuxMi
printf "My Site is %s
" $STATE

Common printf format verbs include: %s – string %d – integer %f – floating‑point number %x – hexadecimal (lowercase) %% – literal percent sign

Comments

Use # at the beginning of a line to add a comment. Multi‑line comments are not supported, but most editors provide shortcuts to comment multiple lines.

# This is a comment

User Input

The read command captures input from the user and stores it in a variable.

echo -n "What do you want? "
read response
echo $response

Arrays

Declare an array by listing elements within parentheses. Access the entire array with ${array[*]} or a specific element with an index.

Countries=('Ubuntu' 'Debian' 'CentOS' "openSUSE" "Linuxmi.com")
echo ${Countries[*]}
echo "${Countries[2]}"

Conditional Statements

Use if‑elif‑else for branching logic, ending with fi. The case statement matches a variable against patterns, ending with esac.

if [[ $a -gt $b ]]; then
  echo "a is greater"
elif [[ $a -lt $b ]]; then
  echo "b is greater"
else
  echo "equal"
fi

NAME=LinuxMi
case $NAME in
  "Debian") echo "Debian is popular" ;;
  "LinuxMi"|"Ubuntu") echo "OpenSUSE" ;;
  *) echo "default case" ;;
esac

Loops

Bash supports C‑style for loops, range for loops, and while loops.

for ((i=0; i<10; i+=2)); do
  echo $i
done

for i in {1..7}; do
  echo $i
done

counter=1
while [ $counter -le 5 ]; do
  echo $counter
  ((counter++))
done

Functions

Define a function by writing its name followed by parentheses and a block of commands. Use return to exit with a status code; to output a value, use echo.

print_working_directory() {
  echo "$PWD"
}
print_working_directory

Beyond Bash

While Bash is powerful for quick automation, other languages such as Python, Go, Ruby, and Rust provide richer features and may be preferable for larger projects.