Unix

Introduction

Unix commands ...

... are small programs (commands and operators).
... are composable, repeatable, and fast.
... have a single purpose.
... are tested and proven.
... enable interaction with operating system.
... were developed during the 60s.
... are commands of the unix operating system.

Standard streams

stdout: = standard output
stdin: = standard input
stderr: = standard error

Shell

Access and interaction with the operating system, which provides different services
Control remote computers
Automation of processes
GUI or CLI
Terminals are used to enter commands, e.g. iTerm, hyper, Git bash, wsl2
e.g. zsh, bash, powershell

Shell shortcuts

arrow up — move upwards in history
arrow down — move downwards in history
code . — open VS code (must be installed)
\[search term] + ENTER — search for [search term] inside the manual and jump to first match
N — search and jump down to next search match
shift + N — search and jump up to previous search match
J — move upwards
K — move downwards
H — move to the left
L — move to the right
tab — autocompletion

Mac

cd ~ — change to home directory
cmd + K — clear history
cmd + N — open new window
ctrl + C — stop running command
ctrl + R — search in history
ctrl + arrow up — move to the left by word separator
ctrl + arrow down — move to the right by word separator
z [project] — navigate into folder including [project] (tool must be installed)

Basic commands

Options

Additions to commands
Various options can be combined
e.g. mkdir OPTION [directory]

General options (flags)

-a — hidden files and directories
-b — branch flag
-h — help flag
-l — show list with all rights
-p — path / parent flag
-s — sort files
-v — verbose flag: shows the execution of the operation step by step
-f — follow file
-g — stands for globally
-r — recursive

Find options

-name — name of the file
-type — type of the file
- d — directory
- f — file
-empty — is the file?
-executable — is the file executable?
-writeable — is the file writable?

Orientation

cd [directory] — navigate into the existing specified directory aka change directory
ls — list files and directories in the current working directory aka list directory contents
ls -la — list all files and directories, also hidden ones, in the current working directory
ls -lah — list all files and directories as a table with header (human readable)
man [command] — show the manual page of the specified command aka command manual
help — shows all internally defined shell commands
help [command] — shows more information about the specified command
history — show all previous commands
pwd — print pathname of the working directory
ps — report a snapshot of the current processes
[program] -v – show version of program installed

Create

mkdir [directory]— make a new directory inside the current working directory
mkdir [parent_directory]/[directory] — add a new folder named [directory] to the existing directory [parent_directory]
mkdir -p [parent_directory] [directory] add a new subfolder [directory] to the parent folder [parent_directory]
touch [file_path] — create a new file with the specified pathname or update the change-timestamp of the file

Read

cat [file] — print out the current content of the specified file aka show file contents
cat [file1] > [file2] — save content of file [file1] to another file [file2]
cat [file1] >> [file2] — append content of [file1] to [file2]
cat hello.md | say — read out content of file "hello.md" via speakers
less [path] — open a pager program for a text file and show file contents by page
open [file_path] — open file with the path [file_path] with default app
head — show the top x lines of a file
tail — show the last x lines of a file

Update

mv [initial_file] [final_file] — rename file
mv [initial_directory] [final_directory] — rename directory
mv [file] [path] — move file, e.g. [path] as ./[directory]
mv [directory] [path] — move directory, e.g. [path] as ../
cp [file] [path] — copy or rename file
echo 'Hi' > [file] — create or replace file named [file] with text content "Hi" aka repeat input
echo 'Ciao' >> [file] — add text content "Ciao" to end of file [file] warnings

Delete

rmdir [directory] — remove the specified directory
rm [file_path] — remove specified file permanently
rm -i [file_path] — ask before removing the file
rm -rf [file_path] — remove file recursively and forced to suppress warnings

Find

find — search file names
find [directory] [options] "[file]/folder]" — find file or directory by name, e.g. find /foo -name bar.md
grep — search file contents
grep [options] [search expression] [directory] — search for expression inside the specified directory, e.g. grep -i "foo" /bar/buzz
grep -iRl [text] [path] — search for text in content of path, show resulting path
zgrep [file] — search inside gzip file

Destroy

pkill — kill process by name

Advanced commands

alias — create and show aliases
curl [url] — download and print online resource (curl stands for client url)
curl [url] | bash — download online resource and execute in shell
curl [url] > [file] — download online resource and save to the specified file
tree [path] — print file tree aka graphical presentation of directories and files (must be installed via brew install tree on Mac or Windows)
tree.com — print directory tree of the current directory (Git bash on Windows)
tree.com //f — print tree with subdirectories and files of the current directory
tree.com //f //a — print tree with subdirectories and files of the current directory as ascii folder structure
reboot — reboot
ssh — connect to online endpoint via secure shell

Glob patterns

. — current directory
.. — parent directory
... — two directories up
name?.text — any single character
name??.text — any two characters
*.log — any number of characters (aka any log file)
./**/index.html — any nested directory (aka any index.html file)
./**/*.html — any number of characters in nested directory (aka any HTML file)
client_[123].txt — any of the given character (1, 2, or 3)
./{index,home}.html — any of the given strings (index or home)

Operators

Control operators

[command] ; [command] — separate commands
[command] && [command] — logical and operator: second command only runs, if first is successful
[command] | [command] — pipeline: send result of first to second command (read from stdout)
[command] & [command] — run first command in background and second command in foreground (e.g. start server, server request, automatic reload if data has been changed)

Redirection operators

[command] > [file_path] — write stdout to file (send output of command (stdout) to file [file_path])
[command] >> [file_path] — append stdout to file (append output of command to the text of the file [file_path])
[command] < [file_path] — read from stdin (send command to file)
[command] 2> [file_path — read from stderr (send error of command (stderr) to file [file_path])

Bash aliases

Shortcuts for unix and Git commands

Syntax

alias name='command(s)'

Instructions

e.g. on Windows

Create a .bash_profile file in the user directory (another common filename: .bashrc)

touch .bash_profile
# pathname: ~/.bash_profile

Create an alias "lah"

echo "alias lah='ls -lah'" > .bash_profile
# Comments are optional
cat .bash_profile

Add another alias "example"

echo "example='x y z'" >> .bash_profile
# Comments are optional
cat .bash_profile

Restart the terminal to load aliases or just source the changed file

source ~/.bash_profile

Bash functions

Bash aliases with one or more arguments
Good to avoid repetition and improve readability
Easy syntax
Two different formats are available to declare functions

Syntax

Format 1

function function_name {
  commands
}

Format 2

function_name () {
  commands
}

Instructions

Open ~/.bash_profile in a text editor

code ~/.bash_profile
# or
nano ~/.bash_profile

Create new bash function and save file

function mkcd {
  mkdir -p -- '$1' && cd -P -- '$1'
}

Reload the changed file

source ~/.bash_profile

SSH-Key

SSH keys are saved to the ~/.ssh folder
The ~/.ssh folder also contains the known_hosts file
There are several types of keys: rsa, dsa, ed25519, ecdsa ...
See the manual page for more details man ssh-keygen

Generate a SSH key of type ed

ssh-keygen -t ed25519 -C "[email protected]"

Generate a SSH key of type rsa

ssh-keygen -t rsa -b 4096 -C "[email protected]"

Add SSH key to the ssh-agent

# Windows
# 1. STEP: Start the ssh-agent in the background
eval `ssh-agent -s`
# 2. STEP Add SSH private key to the ssh-agent
ssh-add ~/.ssh/id_ed25519
# 3. STEP Add SSH public key to clipboard
clip < ~/.ssh/id_ed25519.pub

# Mac
# 1. STEP: Start the ssh-agent in the background
eval "$(ssh-agent -s)"
# 2. STEP Add SSH private key to the ssh-agent (modify the config beforehand if necessary)
ssh-add -K ~/.ssh/id_ed25519
# 3. STEP Add SSH public key to clipboard
pbcopy < ~/.ssh/id_ed25519.pub

Fractalbonita/cheat-sheet-unix-commands.md

Unix

Introduction

Standard streams

Shell

Shell shortcuts

Basic commands

Options

General options (flags)

Find options

Orientation

Create

Read

Update

Delete

Find

Destroy

Advanced commands

Glob patterns

Operators

Control operators

Redirection operators

Bash aliases

Syntax

Instructions

Bash functions

Syntax

Instructions

SSH-Key