% Shell Usage 

# Re-call last input with sudo
sudo !!

# Help
help cd / help dir (...)

# Finding Help
apropos directory / apropos search (...)

# Define custom startup screen
sudo nano /etc/motd

# Run a script as background process
<process> &

#List all running processes
ps -A

# Kill a running process
killall <Process-name>

% Shell System

# Get the current path
pwd

# Get the current hostname
hostname

# Get the current users
users

# Show calendar
cal

# Show today's date
date

# Exit terminal
exit

% Shell Permissions

# Use -R option to change permissions recursively.
ps -ef | grep apache | grep -v grep

# Change group
chgrp <group-name-from> <group-name-to>

% Shell Directories

# List directory contents
ls

# List all directory contents
ll

# List all directory contents sorted by time edited
ls -alt

# List directory (wildcard matching)
ls *.<txt>

# List all files of type
find . -name *.<txt> -print

# Go back to previous directory
cd -

# Make (empty) directory
mkdir <dirname>

# Remove (empty) directory
rmdir <dirname>

# Remove directory with all contents without prompt
rm -rf <dirname>

# Remove directory contents and keep directory
rm -rf *

# Change directory
cd <dirname>

% shell Symlinks

# Create symlink
ln -s <source-dirname> <destination-dirname>

# Update symlink
ln -sfn <source-dirname> <destination-dirname>

# Remove symlink
unlink <sample-dirname>

% Shell Files

# Make (empty) file
touch <filename-txt>

# Duplicate file
cp <filename> <file-copyname>

# Copy/Page folder with content
cp -a <old-folder>/ <new-folder>

# Move/Rename file
mv <current-filename-path> <new-filename-path>

# Move/Rename file and prompt before overwriting an existing file
mv -i <current-filename> <new-filename>

# Remove file
rm <filename-txt>

# Write to file (will overwrite existing content)
cat > <filename-txt> 

# Search for a filename-(not content!) in the current directory
find <filename-txt>

# Search for a string inside all files in the current directory and subdrectories
grep -r <string> *

# Search and replace within file
sed -i s/<original-text>/<new-text>/g <filename-txt>

# MD5 hash for files
md5 <filename-txt>

# MD5 hash for folders
tar c <folder> | md5sum

# Encrypt file
openssl enc -aes-256-cbc -e -in <sample-filename-txt> -out <sample-encrypted-txt>

# Decrypt file
openssl enc -aes-256-cbc -d -in <sample-encrypted> -out <sample-filename>

% Shell Server

# Access via ssh
ssh <username-remote>

# Copy file from server to local
scp <username-remote>:<file-to-send-path> <path-to-recieve> 

# Copy file from local to server
scp <file-to-send> <username-remote>:<where-to-put>

# Escape files with spaces in name like this
<path-to-file>\\\ <name-png>

% Shell System

# Show disc space
df -h

# Show disc space (inodes)
df -i

# Show disc space for current directory
du -hs

# Current processes (also CPS usage)
top or htop

# Show running php processes
ps aux | grep php

# Monitor error log (stream as file grows)
tail error.log -f -n 0

% Shell Apps

# Start appliction
xdg-open <programme> 

# Open finder with current folder
open .

% Shell Variables

# Register variable
export <TESTING>=<Variable-text>

# Echo variable
echo $<Variable>

# Unset variable
unset <Variable>

% Shell Output & Redirects

# Write to file
echo <Hello> > <hello-txt>

# Append content from a file to another file
cat <file1-txt> >> <file2-txt>

# Add the amount of lines, words, and characters to <file2-txt>
cat <file1-txt> | <word-count> | cat > <file2-txt>

# Sort the content of a file (like cat)
sort <hello-txt>

# Save to sorted content to a new file
cat <file1-txt> | sort > <sorted-file1-txt>

# Sort and remove duplicates and save to a new file
sort <file1-txt> | uniq > <uniq-file1-txt>