System Commands

System commands provide information about the running environment, manage processes, and perform system-level operations.

Process Management

ps

Report process status. Usage: ps [options] Examples:

# List all processes
ps

Output example:

$ ps
  PID TTY          TIME CMD
    1 tty1     00:00:00 sh
    2 tty1     00:00:00 node
    3 tty1     00:00:00 ps

The output shows:

Shell (PID 1) - always running
Background jobs with their PIDs
Current command (ps itself)

top

Display system processes interactively. Usage: top Examples:

# Show process monitor
top

Provides a real-time view of:

CPU and memory usage
Running processes
System uptime

kill

Terminate processes by PID or job ID. Usage: kill [signal] pid... Signals:

Default (SIGTERM) - graceful termination
-9 (SIGKILL) - force kill
-STOP - stop/suspend process
-CONT - continue stopped process

Examples:

# Terminate process
kill 1234

# Force kill
kill -9 1234

# Kill background job
kill %1

# Kill multiple processes
kill 1234 5678 9012

Environment

env

Display or set environment variables. Usage: env [name=value...] [command] Examples:

# Display all variables
env

# Set variable for command
env NODE_ENV=production node app.js

# Multiple variables
env FOO=bar BAZ=qux command

Output example:

$ env
PATH=/usr/local/bin:/usr/bin:/bin
HOME=/home/user
USER=user
SHELL=/bin/sh
PWD=/home/user

whoami

Print current user. Usage: whoami Examples:

$ whoami
user

hostname

Show or set system hostname. Usage: hostname [name] Examples:

# Show hostname
hostname

# Set hostname
hostname mycomputer

Output example:

$ hostname
lifo-terminal

System Information

uname

Print system information. Usage: uname [options] Options:

-a - All information
-s - System name
-r - Kernel release
-m - Machine architecture
-o - Operating system

Examples:

# All info
uname -a

# System name only
uname -s

# Kernel version
uname -r

# Architecture
uname -m

Output example:

$ uname -a
Linux lifo-terminal 5.15.0 x86_64 GNU/Linux

uptime

Show system uptime. Usage: uptime Examples:

$ uptime
12:30:45 up 5 days, 3:24, 1 user, load average: 0.15, 0.10, 0.08

free

Display memory usage. Usage: free [options] Options:

-h - Human-readable format
-m - Show in megabytes
-g - Show in gigabytes

Examples:

# Default format
free

# Human-readable
free -h

# Megabytes
free -m

Output example:

$ free -h
              total        used        free      shared  buff/cache   available
Mem:           15Gi       8.2Gi       4.1Gi       256Mi       2.7Gi       6.5Gi
Swap:         8.0Gi       0.0Gi       8.0Gi

fastfetch / neofetch

Display system information in a stylized format. Usage: fastfetch or neofetch Examples:

# Show system info
fastfetch

# Alternative command
neofetch

Displays:

OS and kernel information
CPU and memory specs
Shell and terminal info
ASCII art logo

Date and Time

date

Display or set date and time. Usage: date [options] [+format] Format specifiers:

%Y - Year (4-digit)
%m - Month (01-12)
%d - Day (01-31)
%H - Hour (00-23)
%M - Minute (00-59)
%S - Second (00-59)
%A - Full weekday name
%B - Full month name

Examples:

# Current date and time
date

# Custom format
date +"%Y-%m-%d"
date +"%H:%M:%S"
date +"%A, %B %d, %Y"

# ISO 8601 format
date +"%Y-%m-%dT%H:%M:%S"

# Unix timestamp
date +"%s"

Output examples:

$ date
Sun Mar 01 12:30:45 UTC 2026

$ date +"%Y-%m-%d"
2026-03-01

$ date +"%A, %B %d, %Y"
Sunday, March 01, 2026

cal

Display calendar. Usage: cal [month] [year] Examples:

# Current month
cal

# Specific month
cal 3 2026

# Full year
cal 2026

Output example:

$ cal 3 2026
     March 2026
Su Mo Tu We Th Fr Sa
 1  2  3  4  5  6  7
 8  9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31

Utilities

sleep

Delay for specified time. Usage: sleep duration Duration units:

s - seconds (default)
m - minutes
h - hours

Examples:

# Sleep 5 seconds
sleep 5

# Sleep 2 minutes
sleep 2m

# Sleep 1 hour
sleep 1h

# Use in script
echo "Starting..." && sleep 3 && echo "Done"

watch

Execute command periodically. Usage: watch [options] command Options:

-n seconds - Interval (default: 2)

Examples:

# Watch command every 2 seconds
watch date

# Custom interval
watch -n 5 ls -l

# Monitor file size
watch -n 1 'du -sh /tmp'

bc

Calculator for arithmetic operations. Usage: bc [options] Examples:

# Simple calculation
echo "2 + 2" | bc

# Multiplication
echo "6 * 7" | bc

# Division
echo "scale=2; 10 / 3" | bc

# Power
echo "2 ^ 8" | bc

# Multiple operations
echo "(100 + 50) * 2" | bc

Output examples:

$ echo "2 + 2" | bc
4

$ echo "scale=2; 10 / 3" | bc
3.33

which

Locate command binary. Usage: which command... Examples:

# Find command
which ls
which node
which python

# Multiple commands
which git npm node

Output example:

$ which node
/usr/local/bin/node

Help and Documentation

man

Display manual pages. Usage: man command Examples:

# View manual
man ls
man grep
man tar

help

Display help information. Usage: help [command] Examples:

# General help
help

# Command-specific help
help cd
help export

JavaScript Runtime

node

Execute JavaScript with Node.js. Usage: node [options] [script] [args...] Options:

-e code - Evaluate JavaScript code
-p code - Evaluate and print result

Examples:

# Run script
node script.js

# Evaluate code
node -e "console.log('Hello')"

# Print expression
node -p "2 + 2"

# With arguments
node app.js --port 3000

# REPL mode
node

Output examples:

$ node -e "console.log('Hello, World!')"
Hello, World!

$ node -p "Math.PI"
3.141592653589793

npm

Node package manager. Usage: npm [command] [args...] Common commands:

install - Install packages
run - Run package script
test - Run tests
start - Start application

Examples:

# Install dependencies
npm install

# Install package
npm install express

# Run script
npm run build
npm start
npm test

Package Management

pkg

Package manager for Lifo. Usage: pkg [command] Examples:

# List installed packages
pkg list

# Install package
pkg install package-name

# Update packages
pkg update

Cryptography

sha256sum

Compute SHA-256 hash. Usage: sha256sum [file...] Examples:

# Hash file
sha256sum file.txt

# Multiple files
sha256sum file1.txt file2.txt

# Hash from stdin
echo "hello" | sha256sum

Output example:

$ sha256sum file.txt
2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae  file.txt

Fun Commands

sl

Steam locomotive animation. Usage: sl Examples:

# Run animation
sl

Displays an ASCII art train animation. A playful command for when you mistype ls.

Shell Built-ins

lifo

Lifo system command. Usage: lifo [options] Examples:

# Show version
lifo --version

# System information
lifo info

logout

Exit the shell. Usage: logout Examples:

# Exit terminal
logout

Common Patterns

Background jobs

# Run in background
node server.js &

# List jobs
jobs

# Bring to foreground
fg %1

# Kill background job
kill %1

Process monitoring

# Find process
ps | grep node

# Kill by name
ps | grep node | awk '{print $1}' | xargs kill

System diagnostics

# Full system info
uname -a && free -h && uptime

# Memory usage by process
ps aux | sort -k4 -r | head -10

Scheduled tasks

# Run every 5 seconds
while true; do
  date
  sleep 5
done

Time command execution

date; npm run build; date

Get Started

Core Concepts

Guides

Commands

​Process Management

​ps

​top

​kill

​Environment

​env

​whoami

​hostname

​System Information

​uname

​uptime

​free

​fastfetch / neofetch

​Date and Time

​date

​cal

​Utilities

​sleep

​watch

​bc

​which

​Help and Documentation

​man

​help

​JavaScript Runtime

​node

​npm

​Package Management

​pkg

​Cryptography

​sha256sum

​Fun Commands

​sl

​Shell Built-ins

​lifo

​logout

​Common Patterns

​Background jobs

​Process monitoring

​System diagnostics

​Scheduled tasks

​Time command execution

Build docs developers (and LLMs) love

Process Management

ps

top

kill

Environment

env

whoami

hostname

System Information

uname

uptime

free

fastfetch / neofetch

Date and Time

date

cal

Utilities

sleep

watch

bc

which

Help and Documentation

man

help

JavaScript Runtime

node

npm

Package Management

pkg

Cryptography

sha256sum

Fun Commands

sl

Shell Built-ins

lifo

logout

Common Patterns

Background jobs

Process monitoring

System diagnostics

Scheduled tasks

Time command execution