Basic Bash Shell Scripting

Bash (Bourne Again Shell) is both a command language and a shell for Unix-like systems. Bash scripting means writing a sequence of commands into a file so they can run together — automating file work, user input, loops, and system admin tasks.

Bash scripting turns repeatable steps into clean, versionable scripts that manage systems and solve problems using built-in Unix tools.

Automate repetitive admin tasks (backups, updates).
Create quick solutions for monitoring or file manipulation.
Run a sequence of commands without human interaction.
Configure environments and software setups.
Save time and reduce errors through automation.

Shebang & Execution

The first line #!/bin/bash (the shebang) tells the OS to run the file with Bash. Make it executable and run it:

#!/bin/bash
# file: script.sh

echo "Hello from Bash"

chmod +x script.sh
./script.sh

Variables & Read

name="Mark"
echo "Hi, $name!"

read -p "Your favorite distro? " distro
echo "Nice choice: $distro"

Conditionals

read -p "Enter a number: " n
if [ "$n" -gt 10 ]; then
  echo "Greater than 10"
elif [ "$n" -eq 10 ]; then
  echo "Exactly 10"
else
  echo "Less than 10"
fi

Loops

For — when you know the iteration set; While — continue while condition is true.

# for over values
for i in 1 2 3; do
  echo "Number $i"
done

# for over files in a folder
for f in *.log; do
  echo "Found: $f"
done

# while loop
count=0
while [ $count -lt 3 ]; do
  echo "Count: $count"
  count=$((count+1))
done

Functions

greet(){
  echo "Hello, $1!"
}

greet "Mark"

Functions help you organize code, avoid repetition, and reuse logic across scripts.

Script Structure Tips

Start with #!/bin/bash, then set -euo pipefail for safer scripts.
Quote variables: "$var". Prefer $(cmd) over backticks.
Use functions + main(); return exit codes with exit.
Log progress with echo or printf; use comments generously.

#!/bin/bash
set -euo pipefail

log(){ printf "[%s] %s\n" "$(date +%T)" "$*"; }
main(){
  log "Starting"
  # work goes here
  log "Done"
}
main "$@"

1) Hello World

2) User Input

3) File Existence Check

4) For Loop

5) Simple Backup Script

6) Function Example

We covered the essentials of Bash scripting — shebang, variables, input, conditionals, loops, and functions — then applied them in practical examples. Keep experimenting and check man bash for deeper options.

What is Bash Shell Scripting?

Why and When is Bash Scripting Beneficial?

Bash Scripting Fundamentals