Bash, Shell & Linux Cheat Sheet

# Print current directory
pwd

# List files
ls

# Long format
ls -l

# Show hidden files
ls -la

# Change directory
cd /path/to/folder

# Go home
cd ~

# Go back one directory
cd ..

# Go to previous directory
cd -

# Create empty file
touch notes.txt

# Create directory
mkdir projects

# Create nested directories
mkdir -p app/src/components

# Copy file
cp file.txt backup.txt

# Copy directory
cp -r folder backup-folder

# Move or rename
mv old.txt new.txt

# Remove file
rm file.txt

# Remove directory and contents
rm -r folder

# Print entire file
cat file.txt

# View file page by page
less file.txt

# First 10 lines
head file.txt

# Last 10 lines
tail file.txt

# Follow file updates live
tail -f app.log

# Make script executable
chmod +x script.sh

# Owner can read/write/execute, group and others can read/execute
chmod 755 script.sh

# Owner can read/write, group and others can read
chmod 644 file.txt

# Change file owner
sudo chown user:user file.txt

# Show file permissions
ls -l

read    = 4
write   = 2
execute = 1

7 = 4 + 2 + 1 = rwx
6 = 4 + 2     = rw-
5 = 4 + 1     = r-x
4 = 4         = r--

# Search text inside a file
grep "error" app.log

# Case-insensitive search
grep -i "error" app.log

# Recursive search
grep -r "TODO" .

# Show line numbers
grep -n "error" app.log

# Find file by name
find . -name "app.py"

# Find all .js files
find . -name "*.js"

# Count lines, words, and characters
wc file.txt

# Sort lines
sort names.txt

# Remove duplicate lines
uniq names.txt

# Sort and remove duplicates
sort names.txt | uniq

# Print selected columns
awk '{print $1}' file.txt

# Replace text
sed 's/old/new/g' file.txt

# Pipe output from one command into another
cat app.log | grep "error"

# Count matching lines
grep "error" app.log | wc -l

# Sort unique IPs from log file
awk '{print $1}' access.log | sort | uniq

# Write output to file
echo "hello" > file.txt

# Append output to file
echo "new line" >> file.txt

# Redirect errors
command 2> errors.txt

# Redirect output and errors
command > output.txt 2>&1

# Discard output
command > /dev/null 2>&1

# Show running processes
ps aux

# Search for a process
ps aux | grep nginx

# Interactive process viewer
top

# Better process viewer if installed
htop

# Kill process by PID
kill 1234

# Force kill process
kill -9 1234

# Kill by process name
pkill nginx

# Run command in background
python3 server.py &

# Show background jobs
jobs

# Bring job to foreground
fg

# Stop current foreground process
Ctrl + Z

# Stop current command
Ctrl + C

# Show IP addresses
ip addr

# Show routes
ip route

# Test connectivity
ping example.com

# DNS lookup
nslookup example.com

# Better DNS lookup if installed
dig example.com

# Show listening ports
ss -tulnp

# Test HTTP request
curl -I https://example.com

# SSH into a server
ssh [email protected]

# SSH with custom port
ssh -p 2222 [email protected]

# Copy file to remote server
scp file.txt [email protected]:/home/user/

# Copy file from remote server
scp [email protected]:/home/user/file.txt .

# Kernel and system info
uname -a

# Disk usage
df -h

# Directory size
du -sh folder

# Memory usage
free -h

# CPU info
lscpu

# Current user
whoami

# Logged-in users
who

# View system logs
sudo journalctl

# Recent logs
sudo journalctl -n 50

# Follow logs live
sudo journalctl -f

# Authentication logs
sudo tail -n 50 /var/log/auth.log

# Syslog
sudo tail -n 50 /var/log/syslog

#!/bin/bash

name="Xavier"

echo "Hello, $name"

if [ -f "file.txt" ]; then
  echo "File exists"
else
  echo "File does not exist"
fi

#!/bin/bash

echo "Script name: $0"
echo "First argument: $1"
echo "Second argument: $2"
echo "All arguments: $@"
echo "Number of arguments: $#"

#!/bin/bash

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

count=1

while [ $count -le 5 ]; do
  echo "Count: $count"
  count=$((count + 1))
done

#!/bin/bash

greet() {
  local name="$1"
  echo "Hello, $name"
}

greet "Xavier"

# Show command location
which python3

# Show environment variable
echo $PATH

# Show previous command exit code
echo $?

# Make script executable
chmod +x script.sh

# Run script
./script.sh

# Run script with bash
bash script.sh