Class Description

This class deals solely with Linux (read as "cancer" if Steve Ballmer, "GNU/Linux" if Richard Stallman). The class will cover basic use of the command line and progress into shell scripting using bash. It is quite possible that we will morph into a Linux admin class, if the interest is there. All references to operating system concepts, programs, and syntax will exist within the Linux paradigm. We will not be looking at any super user specific information.

Basic Introduction (2.15.2006)

This class consists of introductory concepts and basic commands.

History of Linux

Linux is, strictly speaking, a kernel, which was released in 1991 by Linus Torvalds. The word was derived from "Linus' Minix". It is a Unix clone. Linux is not Unix. Neither is GNU. Linux is released under the GPL v2 only. More information can be found here.

Introduction to Shells

• A command line shell provides a command line interface (CLI) to the OS (specifically, the kernel). GUIs can be considered shells, but we're not going there. Most programs start out as solely CL apps.

• Bourne shell (sh) (UNIX, version 7, 1978)
  • ash (sh compatable, 92K)
  • bash (Bourne again in 1987)
• C shell (csh) (BSD 4.1)
  • tcsh (TENEX c shell)
• ksh (sh/csh mix)
• zsh (is apparently the bomb diggity, though less popular)

Some Initial Commands

• man
• info
• ls
• cd
• pwd
• tab completion
  • single tab to complete a command or path
  • press tab twice if the line is not completed. This means that there are multiple choices that begin with what you have started typing, and all of the possible choices will show up on the screen.
• paths: relative, absolute
• how to access a shell
  • telnet does not exist
  • ssh
  • gui: xterm, gnome-terminal, aterm
  • ctrl-alt-F1 ... ctrl-alt-F6
• mkdir
• touch
• rm
• cp
• mv (as apposed to rename)
• echo
• alias
• date

Directory Structure

Introduction Continued (2.22.2006)

CL Ctrl Keys

More Commands

• ln: creating symbolic / hard links
• chmod
• ps
• reset
• uname
• grep
• find
• locate
• history
• compression (zip, gzip, bzip) and tar
• file
• tac, head, tail, wc,

Meet Bash

• bash is a program, you can run bash from within bash
• startup scripts
  • /etc/profile
  • ~/.bash_profile
  • ~/.bash_login
  • ~/.profile
• another file
  • ~/.bash_history
• login exit script
  • ~/.bash_logout
• non login shell startup
  • ~/.bashrc
• escape character
• commands on more than one line
• variables: assignment and evaluation
• environment
• set
• assignment
• export to environment

• $(<stmt>)

• math - (())
• backticks

• multiple commands (;,&&,||)

• code blocks: { }
• stty -a

Processes

• init - the parent of all processes

• forking (&)

• bg
• fg
• kill, killall
• killing daemon children (ps -l)
• killing zombies (you cannot kill the dead) / orphans
• top

Bash I/O Features

• file descriptors (stdout(1), stdin(0), stderr(2)), 1>, 1>>, 2>, 2>>, &>, 2>&1

• I/O redirection (<,>,<<,>>)

• pipes (|)

Introduction to Text Editors

• vi
• emacs
• pico

Bash Scripting Basics (3.1.2006)

First Bash Script

#!/bin/bash
echo hello, I am a script
sleep 2
echo I am talking to $(whoami)
exit 0

Important Scripting Commands

• clear
• source
• exec
• eval
• exit
• export
• let
• read
• trap
• wait
• test
• tee

Advanced Bash Scripting (3.8.2006)

• loops (for, while)
• comparisons
• arithmetic and string comparisons
• functions
• arrays
• arguments

TBA (3.15.2006)

Example Scripts

Additional Resources

• An excellent resource is the Linux Documentation Project's Advanced Bash Scripting Guide

• Google is your friend.

• man pages