ronlabs/holberton-system_engineering-devops-1

Start learning shell using basic commands

holberton-system_engineering-devops

0x00. Shell, basics

Resources

Read or watch:

• What Is The Shell?
• Navigation
• Looking Around
• A Guided Tour
• Manipulating Files
• Working With Commands
• Reading Man pages
• Keyboard shortcuts for Bash
• LTS
• Shebang

man or help:

• cd
• ls
• pwd
• less
• file
• ln
• cp
• mv
• rm
• mkdir
• type
• which
• help
• man

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

General

• What does RTFM mean?
• What is a Shebang

What is the Shell

• What is the shell
• What is the difference between a terminal and a shell
• What is the shell prompt
• How to use the history (the basics)

Navigation

• What do the commands or built-ins cd, pwd, ls do
• How to navigate the filesystem
• What are the . and .. directories
• What is the working directory, how to print it and how to change it
• What is the root directory
• What is the home directory, and how to go there
• What is the difference between the root directory and the home directory of the user root
• What are the characteristics of hidden files and how to list them
• What does the command cd - do

Looking Around

• What do the commands ls, less, file do
• How do you use options and arguments with commands
• Understand the ls long format and how to display it
• A Guided Tour
• What does the ln command do
• What do you find in the most common/important directories
• What is a symbolic link
• What is a hard link
• What is the difference between a hard link and a symbolic link

Manipulating Files

• What do the commands cp, mv, rm, mkdir do
• What are wildcards and how do they work
• How to use wildcards

Working with Commands

• What do type, which, help, man commands do
• What are the different kinds of commands
• What is an alias
• When do you use the command help instead of man

Reading Man Pages

• How to read a man page
• What are man page sections
• What are the section numbers for User commands, System calls and Library functions

Keyboard Shortcuts for Bash

• Common shortcuts for Bash

LTS

• What does LTS mean?

Requirements

General

• Allowed editors: vi, vim, emacs
• All your scripts will be tested on Ubuntu 14.04 LTS
• All your scripts should be exactly two lines long ($ wc -l file should print 2)
• All your files should end with a new line (why?)
• The first line of all your files should be exactly #!/bin/bash
• A README.md file at the root of the holberton-system_engineering-devops repo, containing a description of the repository
• A README.md file, at the root of the folder of this project, describing what each script is doing
• You are not allowed to use backticks, &&, || or ;
• All your scripts must be executable. To make your file executable, use the chmod command: chmod u+x file. Later, well learn more about how to utilize this command.

More Info

Example of line count and first line

julien@ubuntu:/tmp$ wc -l 12-file_type
2 12-file_type
julien@ubuntu:/tmp$ head -n 1 12-file_type
#!/bin/bash
julien@ubuntu:/tmp$

In order to test your scripts, you will need to use this command: chmod u+x file. We will see later what does chmod mean and do, but you can have a look at man chmod if you are curious.

Example

julien@ubuntu:/tmp$ ls
12-file_type
lll
julien@ubuntu:/tmp$ ls -la lll
-rw-rw-r-- 1 julien julien 15 Sep 19 21:05 lll
julien@ubuntu:/tmp$ cat lll
#!/bin/bash
ls
julien@ubuntu:/tmp$ ls -l lll
-rw-rw-r-- 1 julien julien 15 Sep 19 21:05 lll
julien@ubuntu:/tmp$ chmod u+x lll # you do not have to understand this yet
julien@ubuntu:/tmp$ ls -l lll
-rwxrw-r-- 1 julien julien 15 Sep 19 21:05 lll
julien@ubuntu:/tmp$ ./lll
12-file_type
lll
julien@ubuntu:/tmp$

0x01. Shell, permissions

Resources

Read or watch:

• Permissions

man or help:

• chmod
• sudo
• su
• chown
• chgrp
• id
• groups
• whoami
• adduser
• useradd
• addgroup

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

Permissions

• What do the commands chmod, sudo, su, chown, chgrp do
• Linux file permissions
• How to represent each of the three sets of permissions (owner, group, and other) as a single digit
• How to change permissions, owner and group of a file
• Why cant a normal user chown a file
• How to run a command with root privileges
• How to change user ID or become superuser

Other Man Pages

• How to create a user
• How to create a group
• How to print real and effective user and group IDs
• How to print the groups a user is in
• How to print the effective userid

Requirements

General

• Allowed editors: vi, vim, emacs
• All your scripts will be tested on Ubuntu 14.04 LTS
• All your scripts should be exactly two lines long ($ wc -l file should print 2)
• All your files should end with a new line (why?)
• The first line of all your files should be exactly #!/bin/bash
• A README.md file, at the root of the folder of the project, describing what each script is doing
• You are not allowed to use backticks, &&, || or ;
• All your files must be executable

0x02. Shell, I/O Redirections and filters

Resources

Read or watch:

• Shell, I/O Redirection
• Special Characters

man or help:

• echo
• cat
• head
• tail
• find
• wc
• sort
• uniq
• grep
• tr
• rev
• cut
• passwd (5) (i.e. man 5 passwd)

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

Shell, I/O Redirection

• What do the commands head, tail, find, wc, sort, uniq, grep, tr do
• How to redirect standard output to a file
• How to get standard input from a file instead of the keyboard
• How to send the output from one program to the input of another program
• How to combine commands and filters with redirections

Special Characters

• What are special characters
• Understand what do the white spaces, single quotes, double quotes, backslash, comment, pipe, command separator, tilde and how and when to use them

Other Man Pages

• How to display a line of text
• How to concatenate files and print on the standard output
• How to reverse a string
• How to remove sections from each line of files
• What is the /etc/passwd file and what is its format
• What is the /etc/shadow file and what is its format

Requirements

General

• Allowed editors: vi, vim, emacs
• All your scripts will be tested on Ubuntu 14.04 LTS
• All your scripts should be exactly two lines long ($ wc -l file should print 2)
• All your files should end with a new line (why?)
• The first line of all your files should be exactly #!/bin/bash
• A README.md file, at the root of the folder of the project, describing what each script is doing
• You are not allowed to use backticks, &&, || or ;
• All your files must be executable
• You are not allowed to use sed or awk

More Info

Read your /etc/passwd and /etc/shadow files. Note: You do not have to learn about fmt, pr, du, gzip, tar, lpr, sed and awk yet.

0x03. Shell, init files, variables and expansions

Resources

Read or watch:

• Expansions
• Shell Arithmetic
• Variables
• Shell initialization files
• The alias Command
• Technical Writing

man or help:

• printenv
• set
• unset
• export
• alias
• unalias
• .
• source
• printf

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

General

• What happens when you type $ ls -l *.txt

Shell Initialization Files

• What are the /etc/profile file and the /etc/profile.d directory
• What is the ~/.bashrc file

Variables

• What is the difference between a local and a global variable
• What is a reserved variable
• How to create, update and delete shell variables
• What are the roles of the following reserved variables: HOME, PATH, PS1
• What are special parameters
• What is the special parameter $??

Expansions

• What is expansion and how to use them
• What is the difference between single and double quotes and how to use them properly
• How to do command substitution with $() and backticks

Shell Arithmetic

• How to perform arithmetic operations with the shell

The alias Command

• How to create an alias
• How to list aliases
• How to temporarily disable an alias

Other help pages

• How to execute commands from a file in the current shell

Requirements

General

• Allowed editors: vi, vim, emacs
• All your scripts will be tested on Ubuntu 14.04 LTS
• All your scripts should be exactly two lines long ($ wc -l file should print 2)
• All your files should end with a new line (why?)
• The first line of all your files should be exactly #!/bin/bash
• A README.md file, at the root of the folder of the project, describing what each script is doing
• You are not allowed to use &&, || or ;
• You are not allowed to use bc, sed or awk
• All your files must be executable

More Info

Read your /etc/profile, /etc/inputrc and ~/.bashrc files. Look at some files in the /etc/profile.d directory. Note: You do not have to learn about awk, tar, bzip2, date, scp, ulimit, umask, or shell scripting, yet.

Manual QA Review

It is your responsibility to request a review for your blog from a peer before the projects deadline. If no peers have been reviewed, you should request a review from a TA or staff member.

0x04-loops_conditions_and_parsing

This project is about basic shell scripting below the learning obejctives are listed for this project

Learning Objectives

• How to create SSH keys
• What is the advantage of using #!/usr/bin/env bash over #!/bin/bash
• How to use while, until and for loops
• How to use if, else, elif and case condition statements
• How to use the cut command
• What are files and other comparison operators, and how to use them