Linux/Bash Commands Cheat Sheet — Daily Terminal Reference

A practical Linux command reference — what you actually run from a terminal. Works on most Linuxes and macOS (BSD sed/find have minor quirks; flagged where it matters).

Files & directories

Command	What it does
pwd	Print working directory
ls -lah	List with sizes, permissions, hidden files
cd ~	Go home
cd -	Go to previous directory
mkdir -p a/b/c	Create nested directories
cp file dest / cp -r dir dest	Copy file / directory
mv old new	Move or rename
rm file	Delete file
rm -rf dir	Delete directory recursively (DESTRUCTIVE)
ln -s target link	Symbolic link
touch file	Create empty file / update timestamp
du -sh *	Size of each item in current dir, human-readable
du -sh * | sort -h	Sorted by size
df -h	Disk space free per filesystem
tree -L 2	Visual directory tree, 2 levels deep

Search & find

Command	What it does
find . -name "*.log"	Files matching name
find . -type d -name node_modules	Directories named node_modules
find . -mtime -7	Modified in last 7 days
find . -size +100M	Larger than 100 MB
find . -name "*.tmp" -delete	Find and delete
find . -name "*.js" -exec grep "TODO" {} +	Run command on each match
grep "pattern" file	Lines matching pattern
grep -r "pattern" .	Recursive grep
grep -rni "todo" --include="*.js"	Recursive, case-insensitive, line numbers, only .js
rg "pattern"	ripgrep — much faster than grep
locate filename	Find file by name (uses index)
which python	Path to executable in $PATH

Viewing files

Command	What it does
cat file	Print whole file
less file	Page through file (q to quit, / to search)
head -20 file	First 20 lines
tail -20 file	Last 20 lines
tail -f file	Follow new lines as they arrive (logs)
wc -l file	Count lines

Text processing

Command	What it does
sort file	Sort lines
sort -u file	Sort + remove duplicates
sort -hr	Sort by human-readable numbers, reverse
uniq file	Remove consecutive duplicates (sort first!)
uniq -c	Count occurrences
cut -d',' -f1,3 file.csv	Columns 1 and 3 by comma
awk '{print $1}'	First whitespace-separated field
awk -F',' '{sum += $2} END {print sum}'	Sum column 2
sed 's/old/new/g' file	Substitute (print to stdout)
sed -i 's/old/new/g' file	Substitute in-place
tr 'a-z' 'A-Z'	Translate (e.g., upper case)
jq '.users[].email' data.json	Extract from JSON (separate install)

Pipes & redirection

cmd1 | cmd2          # pipe stdout of cmd1 to stdin of cmd2
cmd > file           # write stdout to file (overwrite)
cmd >> file          # append stdout to file
cmd 2> errors.log    # redirect stderr
cmd > out 2> err     # split stdout and stderr
cmd &> combined.log  # both to one file
cmd < input.txt      # read stdin from file
echo "hi" | tee file # write to file AND stdout

Permissions

Command	What it does
chmod 644 file	rw for owner, r for group/others
chmod 755 file	rwx owner, rx group/others (typical executable)
chmod +x script.sh	Add execute bit
chmod -R 755 dir	Recursive
chown user:group file	Change owner + group
sudo command	Run as root (or another user with -u)

Permission notation: 4=read, 2=write, 1=execute. Add to combine. 755 = 7 (4+2+1) for owner, 5 (4+1) for group + others.

Processes

Command	What it does
ps aux	All running processes
ps aux | grep nginx	Filter for a process
top / htop	Live process viewer (htop is friendlier)
kill <pid>	Send SIGTERM (graceful)
kill -9 <pid>	SIGKILL (force, no cleanup)
killall nginx	Kill all processes by name
cmd &	Run in background
nohup cmd &	Background + survive logout
jobs	List jobs in current shell
fg %1	Bring job 1 to foreground
bg %1	Resume job 1 in background

Networking

Command	What it does
curl -I url	HEAD request — show headers
curl -L url	Follow redirects
curl -X POST -H "Content-Type: application/json" -d '{"a":1}' url	POST JSON
wget url	Download file
ping host	ICMP echo
dig example.com	DNS lookup
nslookup example.com	DNS lookup (older alternative)
ss -tulpn	Open TCP/UDP ports + processes (modern)
netstat -tulpn	Same (legacy)
traceroute host	Path to a host
ip a	Network interfaces

Compression / archives

Command	What it does
tar -czvf out.tar.gz dir/	Create gzipped tar
tar -xzvf in.tar.gz	Extract gzipped tar
tar -xzvf file.tar.gz -C /target/	Extract to specific directory
zip -r out.zip dir/	Create zip
unzip file.zip	Extract zip
gzip file / gunzip file.gz	Single-file compress / decompress

Variables & scripting

# Variable
NAME="Alice"
echo "Hello $NAME"

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

# Conditionals
if [ -f "file.txt" ]; then echo "exists"; fi
if [[ "$1" == "deploy" ]]; then ./deploy.sh; fi

# Loops
for f in *.log; do gzip "$f"; done
for i in {1..5}; do echo $i; done

# Functions
greet() { echo "Hello, $1"; }
greet Alice

# Exit on first error (recommended at top of scripts)
set -euo pipefail

SSH

Command	What it does
ssh user@host	Connect
ssh -p 2222 user@host	Custom port
ssh-keygen -t ed25519	Generate keypair
ssh-copy-id user@host	Install your public key on server
scp file user@host:/path/	Copy file to server
rsync -avz dir/ user@host:/path/	Smart sync (resumable, only deltas)
ssh -L 8080:localhost:80 user@host	Tunnel local 8080 to host's 80

Related tools

Test regex patterns before sed/grep: regex tester. Compute or verify file SHA hashes: hash generator. Decode Base64-encoded payloads (e.g., from environment files): Base64 encoder/decoder.