git-notes.txt

- - - Unix Commands - - -

	pwd	print working directory ; 
			displays the absolute path to where you are

	cd	change directory : 
			navigates to a different directory
		+ arguments :
			absolute or relative path
			no argument will go back to home
			.. goes one filesystem up (can be chained ../..)

	ls	list :
			lists the contents of the present working directory
		+ flags :
			-t : sorts by modification time
			-l : shows in a long format
			-r : reverses the order
			-a : shows all files, even hidden ones
			-d : lists a directory, not its contents
		+ arguments :
			path a directory
			no argument lists current directory

	man	manual :
			prints out a manual for any command
		+ arguments :
			any command

	touch	:
			change file access and modification times
			creates a file if it doesn’t exist
		+ arguments
			file name

	mkdir	make directory : 
			creates a directory
		+ flags
			-p creates a directory tree as many deep as you specify

	history	:
			provides a history of commands
		+ arguments
			integers give you a list of the -- most recent commands

	less	:
			allows user to control movement through the reading of a file

	head	 :
			displays the beginning of a file
		+ flags
			-n +int shows the first int lines of a file

	mv	move : 
		moves a file to a new location (is also used for renaming files)
		+ arguments
			file location

	nano
		text editor

	cat 	concatenate :
			prints a file to the shell / concatenates two files together
		+ arguments
			file names

	cp	copy :
			copies a file or directory
		+ arguments
			file / directory to be copied
			new file / directory name
		+ flags
			-r (recursive) allows directories to be copied

	rm	remove :
			removes a file / directory
		+ arguments
			file / directory to be removed
		+ flags
			-r (recursive) allows directories to be copied

	whoami	:
			returns the name of the current user

	adduser	:
			(must be done in sudo in Linux) adds a new user

	su	switch user :
			switches between users

	exit	:
			exits out of a switched user

	chmod	change mode : 
			changes permissions (mode) for a file / directory
		+arguments
			u/g/o (user / group / other) +/- r/w /x (read / write / execute)
				ex: u-x
				ex: ugo+x
			rwx notation (r = 4, w = 2, x = 1) ugo
				ex: 644

	chown	change owner :
			changes the owner of a file / directory
			must be done in sudo
		+arguments
			new-user:new-group file-name (chown colincoltrera tester.txt)

	top	:
			displays running processes and resources used

	ps	processes :
			lists out running processes
		+option
			aux
				lists all processes running on a machine

	grep	:
		searches for a pattern in an input, filters only lines with that pattern

	fg	foreground :
			resumes a stopped job
		+arguments
			job number (can be seen with jobs)

	jobs	:
			returns a list of processes in current session

	kill	:
			kills a process, using its process ID (sends a TERM signal)
			with option, sends signal to a process
		+options
			-TERM sends a normal TERM signal
			-KILL / -SIGKILL / -9 forces the killing of a process (dangerous)
			-STOP stops a process, can be restarted later
		
	rmdir	remove directory :
			removes an empty directory

- - -  - - -

	|	pipe : 
			pipes first command output to next command
		history | less

	>	redirection operator :
			makes output a new file
		history > terminal-history.txt

	>>	
			adds to the end of an existing file
		history >> old-file.txt
	
	!!
			runs / fills in the previous command

	sudo	super user do :
			runs a command as the super user (root user)

	&
		use after a job command to open the job in the background (ex: top &)

	*
		wildcard representing zero or more characters

	?
		wildcard representing a single character

	[]
		wildcard representing a range of characters 
			[dte] one character d, t, or e
			[0-9] one number 0 through 9 inclusive
			[^a-k] one letter not a-k 

- - -  - - -

	ctr+z
		stops a job, which can be restarted later (sends a STOP signal to process)

	ctr+c
		kills a job (sends the TERM signal to process)

- - - Git Commands - - -

	git config
		change / display email and username, etc.

	git init
		initializes a repository in a directory

	git status
		shows the status of current save repo (branch , untracked files)

	git add
		adds a file to the staging area

	git commit
		commits files from the staging area to the repo
		makes a permanent record of changes
			changes made
			identity of changer
			date and time
			brief message
			universally unique ident for changes
		+ flags
			-m to add a message (speak in the present tense)
			-a skips the staging area and commits all files

	git log
		logs git history

	git branch
		adds branch label where the HEAD is pointing, or shows the branch
		+ argument 
			label

	git checkout
		changes where the HEAD is pointing

	git remote add origin https://github.com/ccoltrera/uge-workshop.git

	git remote -v
		verbose

	git push -u origin master
		(-u sets the preferences for a branch)

	git branch -d git-notes
		deletes a branch, will not be possible if master doesn’t have changes
		(can use -D if branch changes not in master)

- - - Notes - - -

Paths
	Paths that start with a / are absolute

Root
	topmost container of a filesystem
	generally restricted to admin users
	never delete anything located directly in the root

var
	for things that change regularly (like logs)
etc
	for files that don’t change regularly
tmp
	for temporary files, gets deleted regularly

Flags
	modify how commands work
	can be combined together ( -lt , -tl , -l -t , -t -l)

Naming
	separate words with - , _ , or with “camel spacing” (myFolder)
	don’t use spaces, because they can be a bitch in UNIX
	Linux is case sensitive, OSX is case insensitive (commands are, however)

Pipe ( | )
	chains commands together
	outputs the first command and uses it as input to the second

Hidden files
	files that begin with a dot (.) are default hidden

‘Dirtying the directory’
	anything that makes the working directory and repo different

Process
	an instance of a program 

Job
	a process that you own

Signal
	a message sent to a process by the operating system


** Git only changes files it’s tracking. Files changed in the working directory that aren’t in the repo won’t be affected by git


- - - Git Directories - - -

$git status

Working directory		Staging area		Repo
-----------------		------------		----
unix_notes.txt


$git add unix_notes.txt

Working directory		Staging area		Repo
-----------------		------------		----
unix_notes.txt		unix_notes.txt


$git commit -m ‘add unix notes’

Working directory		Staging area		Repo
-----------------		------------		----
unix_notes.txt					unix_notes.txt




- - - Visualizing Git - - -


$git init

[A]
 ^master
 ^HEAD

$git commit

[A]——————————[B]
		^master
		^HEAD

$git branch git-notes

[A]——————————[B]
		^master
		^HEAD
		^git-notes

$git checkout git-notes
$git commit

[A]——————————[B]——————————[C]
		^master	^HEAD
				^git-notes


$git checkout master
$git commit

[A]——————————[B]——————————[C]
		|		^git-notes
		|
	      [D]
		^master	
		^HEAD