An Introduction to Linux and UNIX for Newbies
The Opensource Club

Isaac Jones

10/7/2001

Introduction

The Opensource Club

The Opensource Club is a group of Opensource and Free Software advocates. We are here to encourage the use of software which improves your freedom.
The Opensource Club Web page:
http://opensource.cis.ohio-state.edu/
schedule of events:
http://opensource.cis.ohio-state.edu/events/index.html
this talk: http://opensource.cis.ohio-state.edu/lectures/newbies/

The Philosophy of Free Software

From the GNU web page: Free software is a matter of freedom: people should be free to use software in all the ways that are socially useful. Software differs from material objects-such as chairs, sandwiches, and gasoline-in that it can be copied and changed much more easily. These possibilities make software as useful as it is; we believe software users should be able to make use of them.
Further Reference: http://www.gnu.org/philosophy
While there is a practical difference between Open Source and Free Software, we will not talk about that here & now. The opensource club supports both Free Software and Opensource Software.

Technical Aspects of free software:

Since you have access to the source code, you can alter it in order to improve the software and to customize it. You can verify for yourself that the software is secure, that it contains no viruses or backdoors, that its not spying on you and sending information to the government (if you live in a country where you can't trust the government) or to anyone else.

Linux and UNIX are very similar. From a user's perspective there is hardly any difference, so virtually everything you learn in this talk can be applied to both Linux, UNIX, and any of the BSD systems. This talk will focus mainly on Linux, and the UNIX environment we use at the CIS department.

Configuration for this tutorial

We're going to create a remote X session on a machine that I run. You may also use the CIS Department's UNIX machines if you want to work there (you'll have to change your shell, but thats explained below.)

So log into your CIS account if you want to use that instead of Linux, or get to the Login point on the Xterm in front of you. Please share your terminal with the person sitting next to you, as we'll go through lots of examples which you will probably want to try on your own.

bash shell navigation

What is a shell

"The shell's job is to translate the user's command lines into operating system instructions."

Run some commands (xchat, xemacs, mozilla, ls, xclock)
whoami

Other shells

Other shells include tcsh (default at CIS) but since bash is the default in Linux, we will talk about bash.

how to get bash at cis

run: /usr/contrib/bin/bash

echo $SHELL \# tells you which shell you're using now
passwd -r nis -e #then input:
/usr/contrib/bin/bash

Directory Structure

Files and Directories (``Folders'') are organized in a tree hierarchy. This should be familiar from MacOS or Windows.
``pwd'' tells you what directory you're in now.
/ is the root of everything. ``cd /''
```
~/ means "your" home directory
```

Command history and realted topics

After running some commands
use arrow keys or C-p & C-n to go back & forth in the history
find . -print | xargs grep "mail" #like rgrep
If you know what command in the history you're looking for, after running a few more commands, I can use C-r to search backwards for "mail" without having to scroll up, this is part of emacs editing mode.

shell vars

echo $SHELL #we did this before
echo $TERM
echo $PAGER
echo $PRINTER
echo $TAB TAB

export TEMP=$PS1 #save it for later
export PS1="hi my name is hal: "
export PS1="\t \u@\h: \w\n% "
#if you want to change it back to what it was 
#before:
export PS1=\$TEMP 
 # otherwise, it'll reset next time we run bash,
 # we'll learn later how to save settings like
 # this.

shell variables can affect things besides the shell.

    export TEMP2=$TERM
    export TERM=dumb
    emacs -nw -q
    export TERM=$TEMP2
    emacs -nw -q

The path

in CIS department, controlled w/ 'subscribe' program, but this will not work for bash
a list colon-separated of directories to search to find which program to run when you enter a command
what does the path look like? echo $PATH

type emacs
    export TEMP=$PATH
    export PATH=
    type emacs
    ls
    type ls
    type cd
    export PATH=/usr/bin
    type emacs #its been found
    type ls #still not found
    for FILE in /bin/* ; do  echo "$FILE"; done 
     #emulate ls
    export PATH=/bin/:$PATH
    type ls #now we found it
    export PATH=$TEMP #get our old path back
    export PATH=${HOME}/usr/bin:$PATH 
    #for your own executables

why do echo and cd work? They are built in shell commands, as type tells us: type cd; type echo; type type
type is similar to 'which', but which should not be used in bash because it won't always return the correct answer: on cis dept computers, in bash "type time; which time;"
The current directory '.'
- Sometimes, if you want to run a program in the current 'working' directory, you have to run it like this: ./myprogram
- echo $PATH #do we see :.:? this can be bad, but it makes some things easier.
- why it might be bad: If someone keeps a program called 'ls' in their home directory, and if you have '.' in your path, cd evilMan;ls might execute THEIR version of ls. If they are evil, this can be bad!
- on the other hand, it makes people who are ignorant of the PATH variable happy, because they can run their programs without saying './myGoodProgram'.
- ```
#BUT it still might not help, you should always
#run programs in the current directory with the
# "./" notation
export $PATH=$PATH:.
mkdir temp
cd temp;ls
emacs -nw -q helloWorld.c
  #C program:
  #include <stdio.h>
  int main() {
   printf ("Hello, World.\n");
   return 0;
  }
  C-x C-c ;to exit emacs
gcc helloWorld.c -otest
test #why doesn't my program do anything!?
echo $PATH #dot is in my path
type test 
#oops, test is built in!, it'll get run first
./test 
which test
```
- one thing to note here is not to name your program 'test', or on some systems, you shouldn't name your program a.out this is a common mistake.
- The big lesson: don't put '.' in your path, use the "./" notation instead.
(also works on tcsh)

aliases

ls -l
alias ll='ls -l'
type ll
ll
alias emacs-quick='emacs -nw -q'
emacs-quick
#also can be used for long path names:
mkdir -p ~/tmp/i/really/like/long/path/\
 names/because/im/anal
alias cdFast='cd ~/tmp/i/really/like/long\
 /path/names/because/im/anal'
cdFast
alias emasc=emacs
emasc

similar on tcsh

shell input files

\${HOME}/.bashrc, 
.bash_profile, 
.profile 
(ls -a /etc/skel)

more /etc/skel/{.bash_profile, .bashrc}

.basrhc: add to this file any shell settings that you want to keep: aliases, path settings, shell variables (CVSROOT, PS1), or programs that you want executed whenever you login.

    more ~ijones/.bashrc
    source ~ijones/.bashrc 
    #notice how the prompt changes, since I
    #have a prompt set PS1 in my .bashrc.

.bash\_profile:
for login shells, should probably ``source ~/.bashrc''.
I don't really use this file, except to run my .bashrc.

from the man page 'man bash':

FILES
/bin/bash
    The bash executable #may be elsewhere
/etc/profile
    The  systemwide  initialization  file, executed for
    login shells
~/.bash_profile
    The  personal  initialization  file,  executed  for
    login shells
~/.bashrc
    The individual per-interactive-shell startup file
~/.bash_logout
    The  individual  login shell cleanup file, executed
    when a login shell exits
~/.inputrc
    Individual readline initialization file

bash also uses .profile

IO redirection

redirection is very good for writing test scripts

use `<' to redirect `stdin' (standard input) from a file

cat < ~/.bashrc #just like 'cat ~/.bashrc'

mail newbie < /.bashrc

```
use `>' to redirect `stdout' (standard output) to a file
```
- in case you want to save the output, or look at it later, or if the output is too much to fit on your screen.
- ```
ls /etc ; ls /etc > ectOutput
more etcOutput
```
(redirection also works similarly on tcsh)
we'll talk about pipes after we talk about basic unix utilities, even though they are really part of the shell. Using a pipe is redirection of the output from one program to the input to another.

Misc

editing modes set -o emacs || set -o vi
- emacs: back: M-b, forward: M-f, beginLine: C-a, endLine: C-e
Further Reference published by O'Reilly:
``Learning the bash shell'' http://www.oreilly.com/catalog/bash2/
``Using CSH and TCSH'': http://www.oreilly.com/catalog/tcsh/

Basic Unix Utilities

man, xman, info, apropos
- UNIX built-in help, use these to get information on almost any Unix program.
- man ls; man man; man info; man xman;
- apropos "X windows": shows you commands with the word X Windows in the title.
file browsers are similar to such things on windows, they give you a graphical view of your file hierarchy.
- konqueror (KDE)
- gmc (gnome)
- nautilus (gnome)
- /usr/dt/bin/dtfile (CDEvil)
ls, mkdir, cp, cd, etc:
more, less, cat: to view files, cat to concatinate files
- more /.bashrc
- less $MAIL
- ```
cat file1 file2>file3
```
find stuff
- find
- find . -name *substring*
- locate: uses a database which it rebuilds periodically, so it doesnt have to search the entire hard drive.
- whereis: will find binaries, source, and man pages for a command
tar, gtar, zip: are used for compression
- gzip myfile; gunzip myfile
- tar -zcvf mydir.tgz mydir#zip, create, verbose, filename
- zip & unzip are similar
secure stuff:
- ssh replaces telnet (also sets DISPLAY)
- stdsun script on CIS: helps manage ssh keys and use the stdsun alias at the same time, since the IP address is always different when using stdsun.
- scp: securely copy from one computer to another, uses ssh
  scp ijones@monk.syntaxpolice.org:/home/ijones/tmp/myfile ./myfile
script FIXME
grep: search through a file w/ regular expressions. REs are too complex to talk about here, but for simple text searching, grep is also useful. It searches a file for a string. grep bash .* egrep b.sh .* egrep b*sh grep -r "love affair" /Mail

pipes (and programs that like pipes)

piping is redirection of stdout, instead of redirecting it to a file, you can redirect it to the input of a program, like connecting two pipes together. Use the $\vert$ character.
you can redirect to any old program

more, less

ls /etc | less
#whenever output is too big, you can use | less
#use q to quit less, :n for next file, / to search

tee: records stdout in a file, but also displays it to stdout (the screen)
```
      ls * |tee teeFile
      ls /etc/|tee teeFile2|less
```

grep

 who | grep ijones
 ls /etc|grep net #see all files containing net

xargs: run a command using stdin as the arguments to the command

find . -print | xargs grep "mail" #like rgrep
find . -name *.cpp |xargs less
 #as opposed to:
find . -name *.cpp |less

bash (shell) builtins

source: execute a shell script within this environment
pushd, popd: change directories
```
 pushd . 
 cd 
 pwd
 popd
```

File Permissions (in brief)

ls -l #see groups and file permissions

chmod

info chmod to learn more

chmod (u | g | o | a) (+ | -) (r | w | x) are the basics
chmod u+x myProgram
#to make a script or program executable perl
 #example
chmod a+rx ${HOME}/WWW                  
chmod -R a+rX ${HOME}/WWW 
#will make all your WWW files world readable

umask: sets the default file permissions (man umask)
groups: the 'g' flag above stands for group. (use ls -l to see the group that owns a file, use 'groups' to see what group your in, use chgrp to change the group of a file you own)

The X Windows System (in brief)

What is it: The X Windows System is a portable, network-transparent window system. It is what makes Unix look like the MacOS or Windows with dialog boxes, menus, etc.
X remote w/ ssh: ssh can configure your remote x session for you. How to do this depends on which version of ssh you have.
```
ssh -X theta.cis.ohio-state.edu
 #with the version on debian
man ssh 
 #for how to do it with your version
```
vnc (eXceed): Remote access to a full X Session, as if you were on the computer. You are doing this now, the terminals you're using are talking to a machine which may be anywhere on the internet. I recommend using vnc as it is generally faster on low bandwidth networks.
```
see http://www.cis.ohio-state.edu/~rowland/vnc
```
DISPLAY, xhost. If you don't use ssh, then you may have to configure the DISPLAY variable and the xhost permissions by hand. Its best to use ssh!
window managers and windowing environments
- gnome
- KDE
- fvwm
- sawfish
- which to choose? Everyone likes a different one! Try using gnome and KDE if you like fancy stuff.

More Resources

The Opensource Club Web page:
http://opensource.cis.ohio-state.edu/

``Learning the bash shell'', published by

O'Reilly: http://www.oreilly.com/catalog/bash2/

``Beginning Linux Programming'', published by Wrox Press
http://www.linuxdoc.org/
http://www.linuxdoc.org/HOWTO/

Important stuff thats outside the scope of this talk, these things will be covered in later talks

Configuring The X Windows System
basic emacs (the extensable text editor)
word processing (abbyword, staroffice, latex)
printing, -p -oduplex, -onobanner
root Access
installation
programming utilities (future talk)
distinction between different Linux distros & different bsd versions
basic program installation (tar, zip, make;make install)

About this document ...

An Introduction to Linux and UNIX for Newbies
The Opensource Club

This document was generated using the LaTeX2HTML translator Version 2K.1beta (1.48)

The command line arguments were:
latex2html -split 0 newbiesTalkOutline -dir newbiesTalkWeb

The translation was initiated by Isaac Jones on 2001-10-02

Isaac Jones 2001-10-02

An Introduction to Linux and UNIX for Newbies The Opensource Club

An Introduction to Linux and UNIX for Newbies
The Opensource Club