Linux & Bash Cheat Sheet: Commands Every Dev Needs

Quick reference tables

Command	What it does
`pwd`	Print current directory
`ls`	List files
`ls -la`	List all files with details (including hidden)
`ls -lh`	Human-readable file sizes
`cd /path`	Change to absolute path
`cd ~`	Go to home directory
`cd -`	Go to previous directory
`cd ..`	Go up one level
`tree`	Show directory tree
`tree -L 2`	Tree limited to 2 levels deep

File operations

Command	What it does
`touch file.txt`	Create an empty file
`mkdir dir`	Create a directory
`mkdir -p a/b/c`	Create nested directories
`cp file dest`	Copy file
`cp -r dir dest`	Copy directory recursively
`mv file dest`	Move or rename file
`rm file`	Remove a file
`rm -r dir`	Remove directory recursively
`rm -rf dir`	Force remove (no prompts — careful!)
`ln -s target link`	Create a symbolic link

Reading files

Command	What it does
`cat file`	Print entire file
`less file`	Scroll through file (q to quit)
`head file`	First 10 lines
`head -n 20 file`	First 20 lines
`tail file`	Last 10 lines
`tail -n 20 file`	Last 20 lines
`tail -f file`	Follow file in real time (logs)
`wc -l file`	Count lines
`wc -w file`	Count words

Searching — grep & find

Command	What it does
`grep "pattern" file`	Search for pattern in file
`grep -r "pattern" dir`	Search recursively in directory
`grep -i "pattern" file`	Case-insensitive search
`grep -n "pattern" file`	Show line numbers
`grep -v "pattern" file`	Invert — lines that don’t match
`grep -l "pattern" dir/*`	List files containing pattern
`find . -name "*.js"`	Find files by name pattern
`find . -type f -name "*.log"`	Find files only (not dirs)
`find . -type d -name "node_modules"`	Find directories by name
`find . -mtime -7`	Files modified in last 7 days
`find . -size +10M`	Files larger than 10MB

Permissions

Command	What it does
`ls -l`	Show permissions in listing
`chmod 755 file`	Set permissions (rwxr-xr-x)
`chmod +x file`	Make file executable
`chmod -R 755 dir`	Set permissions recursively
`chown user file`	Change file owner
`chown user:group file`	Change owner and group
`chown -R user:group dir`	Change ownership recursively
`sudo command`	Run as superuser
`su - user`	Switch to another user

Permission numbers:

Number	Permissions
`7`	rwx (read + write + execute)
`6`	rw- (read + write)
`5`	r-x (read + execute)
`4`	r— (read only)
`0`	--- (no permissions)

Processes

Command	What it does
`ps aux`	List all running processes
`ps aux \| grep node`	Find a specific process
`top`	Live process monitor
`htop`	Better live process monitor
`kill PID`	Kill a process by ID
`kill -9 PID`	Force kill
`killall node`	Kill all processes named `node`
`pkill -f "pattern"`	Kill processes matching pattern
`bg`	Resume stopped job in background
`fg`	Bring background job to foreground
`jobs`	List background jobs
`nohup cmd &`	Run command immune to hangup

Disk & memory

Command	What it does
`df -h`	Disk space usage (human-readable)
`du -sh dir`	Size of a directory
`du -sh *`	Size of each item in current dir
`free -h`	RAM usage
`lsblk`	List block devices (disks)

Networking

Command	What it does
`ip a`	Show IP addresses
`ip r`	Show routing table
`ping host`	Ping a host
`curl url`	Fetch a URL
`curl -I url`	Show HTTP headers only
`curl -o file url`	Download to a file
`wget url`	Download a file
`ss -tulnp`	Show listening ports
`netstat -tulnp`	Show listening ports (older)
`ssh user@host`	SSH into a remote machine
`scp file user@host:/path`	Copy file to remote
`rsync -avz src/ dest/`	Sync directories

Archives & compression

Command	What it does
`tar -czf archive.tar.gz dir/`	Create gzipped tar archive
`tar -xzf archive.tar.gz`	Extract gzipped tar
`tar -tzf archive.tar.gz`	List contents without extracting
`zip -r archive.zip dir/`	Create zip archive
`unzip archive.zip`	Extract zip
`gzip file`	Compress a file (replaces original)
`gunzip file.gz`	Decompress

Pipes, redirects & shortcuts

Symbol	What it does
`cmd1 \| cmd2`	Pipe output of cmd1 to cmd2
`> file`	Redirect stdout to file (overwrite)
`>> file`	Redirect stdout to file (append)
`2> file`	Redirect stderr to file
`2>&1`	Redirect stderr to stdout
`&> file`	Redirect both stdout and stderr
`/dev/null`	Discard output
`< file`	Read stdin from file
`cmd &`	Run command in background

Shell keyboard shortcuts

Shortcut	What it does
`Ctrl+C`	Kill current process
`Ctrl+Z`	Suspend current process
`Ctrl+D`	Exit shell / EOF
`Ctrl+L`	Clear screen
`Ctrl+A`	Jump to start of line
`Ctrl+E`	Jump to end of line
`Ctrl+U`	Delete from cursor to start of line
`Ctrl+K`	Delete from cursor to end of line
`Ctrl+W`	Delete word before cursor
`Ctrl+R`	Search command history
`↑` / `↓`	Navigate command history
`!!`	Repeat last command
`!$`	Last argument of previous command
`!cmd`	Run most recent command starting with `cmd`

Variables & environment

Command	What it does
`VAR=value`	Set a local variable
`export VAR=value`	Set an environment variable
`echo $VAR`	Print a variable
`env`	Show all environment variables
`unset VAR`	Remove a variable
`printenv PATH`	Print a specific env variable
`source ~/.bashrc`	Reload shell config
`which cmd`	Show path to a command
`type cmd`	Show how a command is interpreted

Detailed sections

Pipes — the real power of the terminal

Pipes (|) connect commands so the output of one becomes the input of the next.

# Find all .js files and count them
find . -name "*.js" | wc -l

# See the 10 largest files
du -sh * | sort -rh | head -10

# Search running processes for 'node' and kill them
ps aux | grep node | awk '{print $2}' | xargs kill

# See only unique lines in a file
cat file.txt | sort | uniq

# Count occurrences of each word
cat file.txt | tr ' ' '\n' | sort | uniq -c | sort -rn | head -20

Grep — search like a pro

# Search recursively, show filename and line number
grep -rn "TODO" ./src

# Search for multiple patterns
grep -E "error|warning|critical" app.log

# Show context around matches (3 lines before and after)
grep -C 3 "error" app.log

# Count matches per file
grep -rc "TODO" ./src

# Exclude a directory
grep -r "pattern" . --exclude-dir=node_modules

Find — locate files quickly

# Find and delete all .DS_Store files
find . -name ".DS_Store" -delete

# Find files modified in the last 24 hours
find . -mtime -1 -type f

# Find files larger than 100MB
find . -size +100M -type f

# Execute a command on each result
find . -name "*.log" -exec rm {} \;

# Find empty directories
find . -type d -empty

Cron — scheduled tasks

Edit the crontab:

crontab -e

Format: minute hour day-of-month month day-of-week command

# Every minute
* * * * * /path/to/script.sh

# Every day at midnight
0 0 * * * /path/to/script.sh

# Every Monday at 9am
0 9 * * 1 /path/to/script.sh

# Every 15 minutes
*/15 * * * * /path/to/script.sh

# First day of every month at noon
0 12 1 * * /path/to/script.sh

List cron jobs: crontab -l Remove all cron jobs: crontab -r

SSH essentials

# Connect to a server
ssh [email protected]

# Connect on a non-standard port
ssh -p 2222 user@host

# Copy a file to a server
scp localfile.txt user@host:/remote/path/

# Copy a directory to a server
scp -r localdir/ user@host:/remote/path/

# Generate an SSH key pair
ssh-keygen -t ed25519 -C "[email protected]"

# Copy your public key to a server (enables passwordless login)
ssh-copy-id user@host

# SSH tunnel (forward remote port 5432 to localhost)
ssh -L 5432:localhost:5432 user@host

Writing shell scripts

#!/bin/bash
set -e    # exit on any error
set -u    # error on undefined variables

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

# Conditionals
if [ -f "file.txt" ]; then
  echo "File exists"
else
  echo "File not found"
fi

# Loops
for file in *.js; do
  echo "Processing $file"
done

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

# Command substitution
DATE=$(date +%Y-%m-%d)
echo "Today is $DATE"

Make it executable: chmod +x script.sh Run it: ./script.sh

See also: SSH & GPG Cheat Sheet for remote access and key management.

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