BASHing Your Way Through Linux

A shell is any program that takes input from the user, translates it into instructions that the operating system can understand, and conveys the operating system's output back to the user.

• i.e. Any User Interface
• Character Based vs. Graphics Based

• Shell is Not Integral Part of OS
  • UNIX Among First to Separate
  • Compare to MS-DOS, Mac, Win95, VM/CMS, OS/2?
  • GUI is NOT Required (So you can configure your system to fit your work environment. Why have a fancy GUI for a file server?)
• Default Shell Can Be Configured
  • chsh -s /bin/bash
  • /etc/passwd
• Helps To Customize Environment

• Bourne - Steven Bourne ~1979 (sh)
• C - Bill Joy ~1981 (csh)
• Korn - David Korn ~1986 (ksh)

• (bash) Korn
• (tcsh) C
• (pdksh) Korn

• Why? Familiar Keystrokes for Command Editing
• set -o vi
• set -o emacs
• Demo of vi keystrokes
  • ESC
  • k,j,l,h
  • \ (file completion)
  • * (file expansion)
  • Refer to vi command set for more

• Environment Variables
  • PWD
  • OLDPWD
  • HOME
  • PATH
  • CDPATH
• alias (alias ls='ls -F')
• function (function myls() {clear; echo Customized List; ls -F})
• .bash_profile & /etc/profile (bash_profile?) ('set -o vi' might go here)

	#!/bin/bash
	while
	true
	do
	cat somefile > /dev/null
	echo .
	done

• ctrl-C to stop a job
• ctrl-Z to suspend a job
• ps vs. jobs
• bg and & for running in the background
• fg for pulling jobs to the foreground
• I/O Redirection (>,<, and |)
• Script Arguments ($1, $2, etc)

• cd, cd ~, cd $HOME, all go to home directory
• cd .., goes to parent directory
• cd name, goes to directory name if it is in the present working directory
• cd /name1/name2/name3, drills down from root until it gets to name3
• cd ~/name, same as cd $HOME/name
• cd ~artimus, goes to home directory of user artimus
• cd ., changes to present working directory (does nothing)