Linux Command Line Essential untuk Developer

Kemampuan menggunakan command line adalah skill fundamental bagi developer. Artikel ini membahas perintah Linux essential yang akan meningkatkan produktivitasmu.

Navigasi File System

Perintah Dasar

# Print working directory
pwd

# List files
ls          # Basic list
ls -la      # Detailed + hidden files
ls -lh      # Human readable sizes
ls -lt      # Sort by time

# Change directory
cd /path/to/dir
cd ..       # Parent directory
cd ~        # Home directory
cd -        # Previous directory

# Create directory
mkdir mydir
mkdir -p parent/child/grandchild  # Create nested

Manipulasi File

# Create file
touch file.txt

# Copy
cp source.txt dest.txt
cp -r sourcedir/ destdir/  # Recursive

# Move/Rename
mv old.txt new.txt
mv file.txt /path/to/dir/

# Remove
rm file.txt
rm -r directory/    # Recursive
rm -rf directory/   # Force (hati-hati!)

# View file content
cat file.txt        # Semua content
head -n 20 file.txt # 20 baris pertama
tail -n 20 file.txt # 20 baris terakhir
tail -f log.txt     # Follow (real-time)
less file.txt       # Scrollable viewer

Text Processing

grep - Search Text

# Basic search
grep "error" log.txt

# Case insensitive
grep -i "error" log.txt

# Recursive search
grep -r "TODO" ./src/

# Show line numbers
grep -n "function" script.js

# Invert match (exclude)
grep -v "debug" log.txt

# Count matches
grep -c "error" log.txt

# Regex
grep -E "error|warning" log.txt

sed - Stream Editor

# Replace text
sed 's/old/new/' file.txt           # First occurrence
sed 's/old/new/g' file.txt          # All occurrences
sed -i 's/old/new/g' file.txt       # In-place edit

# Delete lines
sed '/pattern/d' file.txt           # Lines matching pattern
sed '1,5d' file.txt                 # Lines 1-5

# Print specific lines
sed -n '10,20p' file.txt            # Lines 10-20

awk - Text Processing

# Print columns
awk '{print $1}' file.txt           # First column
awk '{print $1, $3}' file.txt       # First and third

# Custom delimiter
awk -F',' '{print $2}' data.csv

# Conditional
awk '$3 > 100 {print $1}' data.txt

# Sum column
awk '{sum += $2} END {print sum}' data.txt

Other Text Tools

# Sort
sort file.txt
sort -n numbers.txt     # Numeric sort
sort -r file.txt        # Reverse
sort -u file.txt        # Unique only

# Unique
uniq file.txt           # Remove duplicates
uniq -c file.txt        # Count occurrences

# Word count
wc file.txt             # Lines, words, chars
wc -l file.txt          # Lines only

# Cut
cut -d',' -f1,3 data.csv  # Fields 1 and 3

File Permissions

Understanding Permissions

-rwxr-xr-x
│└┬┘└┬┘└┬┘
│ │  │  └── Others: r-x (read, execute)
│ │  └───── Group: r-x (read, execute)
│ └──────── Owner: rwx (read, write, execute)
└────────── File type (- = file, d = directory)

chmod - Change Permissions

# Symbolic mode
chmod u+x script.sh     # Add execute for owner
chmod g-w file.txt      # Remove write for group
chmod o=r file.txt      # Set others to read only
chmod a+r file.txt      # Add read for all

# Numeric mode
chmod 755 script.sh     # rwxr-xr-x
chmod 644 file.txt      # rw-r--r--
chmod 600 secret.key    # rw-------

chown - Change Ownership

chown user file.txt
chown user:group file.txt
chown -R user:group directory/

Process Management

Viewing Processes

# List processes
ps aux                  # All processes
ps aux | grep node      # Filter

# Real-time monitoring
top
htop                    # Better interface (install dulu)

# Process tree
pstree

Managing Processes

# Kill process
kill PID                # Graceful
kill -9 PID             # Force kill
killall processname

# Background/Foreground
command &               # Run in background
jobs                    # List background jobs
fg %1                   # Bring to foreground
bg %1                   # Continue in background
Ctrl+Z                  # Suspend current process

# nohup - survive logout
nohup command &

Networking

Basic Commands

# Check connectivity
ping google.com
ping -c 4 google.com    # 4 packets only

# DNS lookup
nslookup domain.com
dig domain.com

# Network interfaces
ip addr
ifconfig                # Older systems

# Routing
ip route
netstat -rn

# Open ports
netstat -tulpn
ss -tulpn               # Modern alternative

curl - HTTP Requests

# GET request
curl https://api.example.com/users

# POST request
curl -X POST -d '{"name":"John"}' \
  -H "Content-Type: application/json" \
  https://api.example.com/users

# Download file
curl -O https://example.com/file.zip
curl -o myfile.zip https://example.com/file.zip

# Follow redirects
curl -L https://example.com

# Show headers
curl -I https://example.com
curl -v https://example.com  # Verbose

wget - Download Files

wget https://example.com/file.zip
wget -O custom-name.zip https://example.com/file.zip
wget -c https://example.com/large-file.zip  # Resume

Disk Usage

# Disk space
df -h                   # Human readable
df -h /home             # Specific mount

# Directory size
du -sh directory/       # Summary
du -h --max-depth=1     # One level deep

# Find large files
find / -size +100M -type f 2>/dev/null

Compression

# tar
tar -cvf archive.tar files/     # Create
tar -xvf archive.tar            # Extract
tar -tvf archive.tar            # List contents

# tar.gz
tar -czvf archive.tar.gz files/
tar -xzvf archive.tar.gz

# zip
zip -r archive.zip directory/
unzip archive.zip
unzip -l archive.zip            # List contents

Environment Variables

# View
echo $PATH
echo $HOME
env                     # All variables
printenv VAR_NAME

# Set (current session)
export MY_VAR="value"

# Permanent (add to ~/.bashrc or ~/.zshrc)
echo 'export MY_VAR="value"' >> ~/.bashrc
source ~/.bashrc

Pipes dan Redirection

# Pipe output ke command lain
cat file.txt | grep "error" | wc -l

# Redirect output
command > file.txt      # Overwrite
command >> file.txt     # Append
command 2> error.txt    # Stderr only
command &> all.txt      # Both stdout and stderr

# Input redirection
command < input.txt

# Here document
cat << EOF > file.txt
Line 1
Line 2
EOF

Useful Shortcuts

Keyboard Shortcuts

Shortcut	Action
`Ctrl+C`	Cancel current command
`Ctrl+D`	Exit shell / EOF
`Ctrl+L`	Clear screen
`Ctrl+A`	Go to line start
`Ctrl+E`	Go to line end
`Ctrl+R`	Search command history
`Tab`	Autocomplete
`!!`	Repeat last command
`!$`	Last argument of previous command

Command History

history             # Show history
history | grep git  # Search history
!123                # Run command #123
!!                  # Run last command
sudo !!             # Run last command with sudo

Shell Scripting Basics

#!/bin/bash

# Variables
NAME="World"
echo "Hello, $NAME!"

# Conditionals
if [ -f "file.txt" ]; then
    echo "File exists"
elif [ -d "directory" ]; then
    echo "Directory exists"
else
    echo "Not found"
fi

# Loops
for i in 1 2 3 4 5; do
    echo "Number: $i"
done

for file in *.txt; do
    echo "Processing $file"
done

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

Tips Produktivitas

1. Aliases

# Add to ~/.bashrc
alias ll='ls -la'
alias gs='git status'
alias dc='docker-compose'
alias k='kubectl'

2. Useful One-liners

# Find and replace in multiple files
find . -name "*.js" -exec sed -i 's/old/new/g' {} +

# Kill process by port
kill $(lsof -t -i:3000)

# Watch file changes
watch -n 1 'ls -la'

# Quick HTTP server
python3 -m http.server 8000

3. tmux - Terminal Multiplexer

tmux                    # Start session
tmux new -s name        # Named session
Ctrl+B, %               # Split vertical
Ctrl+B, "               # Split horizontal
Ctrl+B, arrow           # Navigate panes
Ctrl+B, d               # Detach
tmux attach -t name     # Reattach

Kesimpulan

Menguasai command line akan sangat meningkatkan produktivitasmu sebagai developer. Mulai dengan perintah dasar, lalu pelajari yang lebih advanced sesuai kebutuhan.

Tips: Buat cheat sheet pribadi dengan perintah yang sering kamu gunakan!

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