Linux & Bash Cheat Sheet: Commands Every Dev Needs

Quick reference tables

Navigation

File operations

Reading files

Searching — grep & find

Permissions

Permission numbers:

Processes

Disk & memory

Networking

Archives & compression

Pipes, redirects & shortcuts

Shell keyboard shortcuts

Variables & environment

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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