Windows & Linux · Basic Bash Shell Scripting

Basic Bash Shell Scripting

Turn repetitive terminal tasks into small, reusable programs. Learn the shebang, variables, conditionals, loops, and functions—then apply them with real examples.

What is 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.

Why and When is Bash Scripting Beneficial?

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.

Bash Scripting Fundamentals

Shebang & Execution

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

echo "Hello from Bash"

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

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

If/else code example — If/else structure.

If/else output screenshot — If/else output.

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

loop over files output — Loop over files output.

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 "$@"

Script Examples

1) Hello World

2) User Input

read user input code — Prompt with `read`.

3) File Existence Check

4) For Loop

5) Simple Backup Script

6) Function Example

function script output — Execution output.

Conclusion

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.

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