Cara Membuat Bash Script untuk Automation

Bash scripting adalah skill penting untuk automating repetitive tasks di Linux. Mari pelajari dasar-dasarnya.

Creating Your First Script

Basic Script

#!/bin/bash
# This is a comment

echo "Hello, World!"

Make Executable

# Create script file
touch myscript.sh

# Add content
nano myscript.sh

# Make executable
chmod +x myscript.sh

# Run script
./myscript.sh

Variables

Defining Variables

#!/bin/bash

# String variable
name="John"
echo "Hello, $name"

# Number variable
age=25
echo "Age: $age"

# Command output
current_date=$(date)
echo "Today: $current_date"

User Input

#!/bin/bash

echo "What is your name?"
read name

echo "Hello, $name!"

Conditional Statements

If-Else

#!/bin/bash

age=18

if [ $age -ge 18 ]; then
    echo "You are an adult"
else
    echo "You are a minor"
fi

Comparison Operators

# Numeric comparisons
-eq  # equal
-ne  # not equal
-gt  # greater than
-lt  # less than
-ge  # greater or equal
-le  # less or equal

# String comparisons
=    # equal
!=   # not equal
-z   # empty string
-n   # non-empty string

File Tests

#!/bin/bash

file="test.txt"

if [ -f "$file" ]; then
    echo "File exists"
fi

if [ -d "folder" ]; then
    echo "Directory exists"
fi

# Other tests:
# -e exists
# -r readable
# -w writable
# -x executable

Loops

For Loop

#!/bin/bash

# Loop through list
for item in apple banana orange; do
    echo "Fruit: $item"
done

# Loop through numbers
for i in {1..5}; do
    echo "Number: $i"
done

# Loop through files
for file in *.txt; do
    echo "Processing: $file"
done

While Loop

#!/bin/bash

counter=1

while [ $counter -le 5 ]; do
    echo "Count: $counter"
    ((counter++))
done

Functions

Defining Functions

#!/bin/bash

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

# Call function
greet "World"
greet "John"

Return Values

#!/bin/bash

add_numbers() {
    local result=$(($1 + $2))
    echo $result
}

sum=$(add_numbers 5 3)
echo "Sum: $sum"

Practical Examples

Backup Script

#!/bin/bash

# Backup script
backup_dir="/backup/$(date +%Y%m%d)"
source_dir="/home/user/documents"

mkdir -p "$backup_dir"
cp -r "$source_dir" "$backup_dir"

echo "Backup completed: $backup_dir"

System Monitor

#!/bin/bash

echo "=== System Monitor ==="
echo "Date: $(date)"
echo ""
echo "Disk Usage:"
df -h / | tail -1
echo ""
echo "Memory Usage:"
free -h | grep Mem
echo ""
echo "CPU Load:"
uptime | awk '{print $10 $11 $12}'

File Organizer

#!/bin/bash

# Organize files by extension
for file in ~/Downloads/*; do
    if [ -f "$file" ]; then
        ext="${file##*.}"
        mkdir -p ~/Downloads/$ext
        mv "$file" ~/Downloads/$ext/
    fi
done

echo "Files organized!"

Error Handling

Exit Codes

#!/bin/bash

if ! command -v git &> /dev/null; then
    echo "Git not installed"
    exit 1
fi

echo "Git is installed"
exit 0

Set Options

#!/bin/bash

set -e  # Exit on error
set -u  # Error on undefined variables
set -o pipefail  # Fail on pipe errors

Kesimpulan

Bash scripting adalah powerful tool untuk automation. Start dengan simple scripts dan gradually build complexity.