Bash
Bourne Again Shell

The Bourne Again Shell was created for use in the GNU project.  The GNU
project was started by Richard Stallman of the Free Software Foundation
in an effort to create a free version Unix for the ix86 along with all
of the required utilities.  Bash was intended to be the standard shell for this GNU system.  When the complete GNU system failed to materialize Linux came on the scene and it adopted Bash as its standard shell.  Bash is also available for pretty much every other Unix system and for Microsoft Windows.

I.      Pipes and Redirections

	a.  Stdin, Stdout, Stderr
	Every programs has three open "files" to start out with........

	b.  Redirections
	Redirections allow you to take these three things and point them
	to other "files".

	Output redirection
	cat names
	sort names > sorted_names
	sort nofile > outie1  #  Get an error
	sort nofile 2> outie2 #  No error....or is there?
	sort names2 >> sorted_names
	ls -laR /home > files
	ls -laR /home 2> errors
	ls -laR /home &> both
	ls -laR /home/ 1> files 2> errors #to 2 files

	Input Redirection
	./readthings < names  # Makes assignments easier.

	c.  Pipes
	-- Allow one to connect the stdout of one program to the stdin of the
	next
	cut -d: -f1 /etc/passwd
	cut -d: -f1 /etc/passwd | sort
	cut -d: -f1 /etc/passwd | sort > users

II.     Job Control -- Multitasking

	a.  Ctrl Z

	b.  jobs

	c.  fg, bg

III.    Variables

    # Assigning, derefferencing

    a.  Shell Variables
	Variable only available to the current program.
	-- envvar

    b.  Environment Variables
	Variable available to the current or and of its child programs

IV.     Aliases -- in your .bashrc
	alias pn='pine'
	alias yakko='ssh zaphod@yakko.cs.wmich.edu'
	alias l='ls'
	alias ll='ls -la'

V.      Functions

    a.  Can easily be used as multi-command aliases.

	# Take some from work

    b.  Can be used in scripts

VI.     Scripts

    #   Must be executable

    a.  Control Structures
	    
        1.  test or [
        # no spaces for assignment.  Spaces necessary for comparison.

	    2.  if/else
        # You can find a complete list of test options at 
        # http://library.psyon.org/os/linux/abs-guide/

	    3.  for
        # Not like for loops in other languages.  You can't itterate from
        # 1 to 10 for example

	    4.  while and until

	    5.  case

	    6.  select

    b.  Doing Math

    c.  Backticks, quotes, Here-Documents?



Reference URLS

BASH Programming - Introduction HOW-TO
http://www.tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html

Advanced Bash-Scripting Guide
http://library.psyon.org/os/linux/abs-guide/