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=========================== Aliens Bash Tutorial 
==============================\par -----------------Written by Alien <-> 
alien@ktv.koping.se----------------------\par 
===============================================================================\par 
\par First you probably need to read a UNIX command bible to really understand 
this\par tutorial, but I will try to make it as clear as possible, there is 
about\par 100-150 UNIX commands explained later in this tutorial.\par You are to 
have some UNIX experance before starting on this tutorial, so\par if you feel 
that you have UNIX/Linux experance feel free to start to learn\par here.\par 
What I included here is general shell scripting, most common other things\par 
and some UNIX commands.\par Here's the most common shell types:\par \par bash = 
Bourne again shell\par sh = shell\par csh = C shell\par tcsh = Tenex C shell 
(not tab-completion-extended C shell)\par tclsh = Tcl shell\par ksh = korn 
shell\par ash = a shell\par bsh = bourne shell ? (in most Linux distributions 
it's a link to /bin/ash) \par zsh = the Z shell (it's what it's manual page 
tells about it .. :/ )\par \par 
===============================================================================\par 
1 - What you already know. (should know)\par 
===============================================================================\par 
\par Here we go, bash scripting is nothing more then combining lots of UNIX 
commands\par to do things for you, you can even make simple games in bash \par 
(just UNIX commands) or as in normal cases, batch files to control things\par in 
your computer.\par \par There is a variety of easyer and harder examples in the 
beginning of this\par tutorial, I've done it this way to make it easier for 
people to get the \par general picture, so they will get more of the "aha!" 
experiences in the later \par chapters of this tutorial.\par \par What bash or 
any scripting language does is to call for premade programs\par that lives in 
your computer.\par So when you write a command in a script you are calling a 
command that is\par a part of the system.\par That is why this tutorial will be 
just as much a Linux and UNIX tutorial\par as a shell scripting tutorial.\par 
\par I will however not take up much about The X Windows System in this\par 
tutorial, for the simple reason that a Window Manager does nothing else\par then 
display programs.\par This means that a Window Manager is like a graphical shell 
for the system.\par You can do all in this tutorial from any terminal emulator 
in a Linux\par Graphical Enviorment (The X Windows System).\par A terminal 
emulator would be such as: Eterm, xterm, axvt, rxvt, kterm etc.\par A terminal 
emulator let's you get up a terminal with a command prompt\par in a graphical 
window.\par \par 
--------------------------------------------------------------------------------\par 
\par Shell command separator/control characters:\par \par | = pipe will take the 
first commands stdout as the second commands stdin.\par || = OR if first command 
is false, it will take the second.\par |= = OR IS (mostly used in if 
statements)\par && = AND if first command is true, it will execute the second 
one.\par ! = NOT (mostly used in if and test statements), but as a 
shell-command\par it opens a shell to run the command (ex. `! echo foo`)\par != 
= NOT IS (mostly used in if statements)\par !$ = last commands last argument\par 
!! = repeat last command\par = = IS (mostly used in if statements)\par ; = will 
separate 2 commands as if they were written on separate command lines\par ;; = 
end of a case function in a case statement. (see `case` further down)\par $ = 
prefix to a variable like "$myvar"\par $$ = PID of current process (PID == 
Process ID)\par $0 = Shows program that owns the current process.\par $1 = First 
agument supplied after the program/function on execution.\par $2 = Second 
agument supplied after the program/function on execution. ($3 etc.)\par $# = 
Shows the number of arguments.\par $? = Any argument (good to use in `if` 
statements)\par $- = current option flags (I never ever had to use this one)\par 
$_ = Last argument/Command\par $* = All arguments\par $@ = All arguments\par # = 
remmed line, anything on a line after "#" will be overlooked by the script\par 
\{ = start braces (starts a function)\par \} = end braces (ends a function)\par 
[ = start bracket (multiple-argument specifiers)\par ] = end bracket 
(multiple-argument specifiers)\par @ = $@ is equivalent to "$1" "$2" etc. (all 
arguments)\par * = wild card (* can substitute any number of characters)\par ? = 
wild card (? can substitute any single character)\par " = quote\par ' = precise 
quote. (Will even include "'s in the quote)\par ` = command quote. (variable=`ls 
-la` doing $variable will show the dir llist)\par . = dot will read and execute 
commands from a file, ( . .bashrc )\par & = and. as suffix to executed file 
makes it go to the background(./program &)\par 0> = stdin stream director\par 1> 
= stdout stream director (standard output)\par 2> = stderr stream director 
(standard error output)\par % = job character, %1 = fg job 1, %2 = fg job 2, 
etc.\par >> = stream director append to a file\par << = stdin stream director. 
(cat > file << EOF ; anything ; EOF)\par > = stream director that will start at 
the top of the file (in if statements < and > may be used as greater-then and 
lesser-then, as: if [ "$1" >= "2" ])\par \\ = back-slash, takes away any special 
meaning with a character, \par \\$var will not be treated as a variable. \par 
(and a new line will not be treated as a new line)\par >& = stream director to 
stream director, ie. echo "a" 1>/dev/null 2>&1\par this directs 2> to the same 
place as 1>\par \par 
--------------------------------------------------------------------------------\par 
\par Here is the basic UNIX or rather Linux directory structur:\par \par 
\tab\tab\tab\tab / (system root)\par 
_______________________________|____________________________________\par | |\tab 
|\tab | | |\tab |\tab |\tab |\tab | | |\par bin/ boot/ dev/ etc/ home/ lib/ 
lost+found/ proc/ root/ sbin/ usr/ var/\par | | | | | | | | | | | |\par | | | | 
| | | | | | | |-> various\par | | | | | | | | | | |\par | | | | | | | | | | |-> 
Read later..\par | | | | | | | | | | \par | | | | | | | | | |-> Superuser 
Binarys\par | | | | | | | | |\par | | | | | | | | |-> User roots home dir\par | 
| | | | | | | \par | | | | | | | |-> system info etc.\par | | | | | | | \par | | 
| | | | |-> Orphan files (look here after crashes) \par | | | | | | \par | | | | 
| |-> System / programming librarys\par | | | | | \par | | | | |-> Contains the 
user accounts home directorys \par | | | |\par | | | |-> System configuration 
files.\par | | |\par | | |-> Devices\par | |\par | |-> The kernel and kernel 
maps.\par |\par |-> Executeble files. (binarys)\par \par \par 
--------------------------------------------------------------------------------\par 
\par Here's an example of the following files locations:\par \par /dev/null\par 
/dev/fd0\par /etc/passwd\par /home/alien/.profile\par /usr/local/bin/BitchX\par 
\par / \par 
_______________________________|____________________________________\par | | | | 
| | | | | | | |\par bin/ boot/ dev/ etc/ home/ lib/ lost+found/ proc/ root/ 
sbin/ usr/ var/\par | | | | \par | | alien/ local/\par | | | |\par | | |-> 
.profile | \par | |-> passwd bin/ \par | |\par |-> null |-> BitchX\par |-> 
fd0\par \par 
--------------------------------------------------------------------------------\par 
\par And a final example that's a bit more stripped, just incase you are 
really\par new to computers.\par Here following files locations:\par \par 
/dev/null\par /dev/audio\par /dev/hda1\par /etc/passwd\par /etc/shadow\par 
/home/alien/.profile\par /home/alien/tmp/somefile\par 
/home/user/.bash_profile\par /usr/local/bin/BitchX\par /sbin/shutdown\par \par 
/\par _____________________________|_____________________________\par | | | | | 
\par dev/ etc/ home/----- usr/ sbin/ \par | | | | | |\par |-> null | | | local/ 
|-> shutdown\par |-> audio | | | | \par |-> hda1 | | | bin/ \par |-> passwd 
alien/ | |\par |-> shadow | user/ |-> BitchX\par | |\par | |-> .bash_profile\par 
|\par |-> .profile\par |\par tmp/\par |\par |-> somefile\par \par 
--------------------------------------------------------------------------------\par 
\par This is the same structure as on any computer that uses directorys.\par 
Though some of the directory names are UNIX specific.\par No further explanation 
should be nessesary.\par \par After reading this tutorial, brows around the 
system and try to learn\par what all the files does, just dont remove any files 
you didnt put there\par until your ABSOLUTLEY sure of what you are doing.\par 
\par 
--------------------------------------------------------------------------------\par 
\par Here's a few UNIX commands just for illustration:\par \par echo \par 
======\par \tab echo will *echo* anything you add to it like this:\par \par \tab 
alien:~$ echo "blah"\par \tab blah\par \tab alien:~$\par \tab\par \tab To get it 
to echo without a new line add the suffix -n\par \tab like this:\par \par \tab 
alien:~$ echo -n "blah "\par \tab blah alien:~$\par \par \tab I'll get back to 
why you want to do "-n" sometimes in a while.\par \par read\par ======\par \tab 
read will read from the keyboard (stdin) and save it as a variable\par \tab the 
variable name goes after the read command, like this:\par \tab\par \tab alien:~$ 
read myvar\par \tab \par \tab alien:~$ echo $myvar\par \tab blah\par \tab 
alien:~$\par \par \tab To combine these two commands (echo and read) in a small 
script\par \tab line, it can look like this:\par \tab\par \tab alien:~$ echo -n 
"password: " ; read pass ; echo "Your pass is $pass"\par \tab password: \par 
\tab Your pass is mypass\par \tab alien:~$\par \par \tab Get the basic idea 
?\par \par 
--------------------------------------------------------------------------------\par 
\par Anyway, here are some commands that you should know before moving on with 
this\par tutorial - \par [*] after == important to know.\par [X] after == very 
basics will do.\par \par ls\tab [*]\par echo\tab [*]\par cat\tab [*]\par 
less\tab [X]\par head\tab [X]\par tail\tab [X]\par grep\tab [*]\par chmod\tab 
[*]\par chown\tab [X]\par \par Some applications you need to know how to operate 
(basics will do) :\par \par any text editor (preferably emacs or vi)\par 
telnet\par lynx\par ftp (ncftp)\par \par These are all explained later in this 
tutorial.\par \par 
--------------------------------------------------------------------------------\par 
\par Now don't sit there and ask yourself how's going to teach you the 
commands\par or applications I just listed here above. use the manual pages.\par 
like this:\par \par man echo\par \par that will get you the full manual on the 
command echo :)\par man works the same way with applications that you have the 
manual pages for.\par \par To get out of the manual page just press the letter 
"q".\par "q" quits it and bet's you back to the command line prompt.\par man 
uses all the normal "less" commands.\par \par Or read further down in this 
tutorial in the basic Linux/UNIX commands and \par operations section (8).\par 
\par 
--------------------------------------------------------------------------------\par 
\par The key to shell scripting just as with any programming language/Operating 
\par System is to REALLY understand what you are doing, so do read this file\par 
more then once, and don't read it to fast.\par Take your time and let it sink 
in, so you know what it's all about,\par and do take time to read manual pages 
and do some playing with the commands\par so you learn them.\par \par Now that 
should be enough of what you *should* know before starting to learn\par UNIX 
shell scripting.\par \par So here we go.......\par \par 
===============================================================================\par 
2 - Where to start\par 
===============================================================================\par 
\par You should always start with very simple scripts that you really don't 
have\par any practical use for but still *could* be of practical use =)\par \par 
As for first let's make what we already know to a *real* executable script.\par 
Open a text editor (name the file myscript.sh) and type this:\par \par \par \par 
#!/bin/bash\par \par echo -n "password: " \par read pass \par echo "Your pass is 
$pass"\par \par \par \par save & exit --- then do this command: chmod u+x 
myscript.sh\par Then we can execute it:\par \par \tab alien:~$ ./myscript.sh\par 
\tab password: \par \tab Your pass is \par \tab alien:~$\par \par The 
"#!/bin/bash" at the start of the file is to let the script know what\par shell 
type it should use.\par \par The "chmod u+x myscript.sh" is to make it 
executable. \par (change-mode user+execute-right-on myscript.sh) ..... read the 
manual pages\par on chmod for more info on it =)\par \par 
--------------------------------------------------------------------------------\par 
\par Take alot of time to play around in your system, open files, figure out\par 
what they do (but don't edit or remove them).\par \par Take time also to learn 
some good text editor, that's important.\par Learn, emacs or vi, those are by 
most people considerd the absolutly best,\par but jed, joe, elvis, pico or any 
simple editor like that will do \par just fine for now.\par \par emacs and vi 
are explained later in this tutorial.\par \par 
--------------------------------------------------------------------------------\par 
\par Another thing before moving on is that you can export a variable from a\par 
script.\par \par Say that you have the variable "$var" in a script and want to 
export\par it to the system for use with some other script or something, you 
can\par do: export var\par \par Like this little script:\par \par 
--------------------------------------------------------------------------------\par 
\par #!/bin/bash\par \par VAR="10"\par export VAR\par \par 
--------------------------------------------------------------------------------\par 
\par But more to how to make scripts in a second, I just thought that this 
would\par be a good time to enlighten you about this.\par \par So here we go 
....\par \par 
===============================================================================\par 
3 - Beginning techniques.\par 
===============================================================================\par 
\par First off I'm going to show how to count in bash or how to use your 
command\par line as a calculator, which is really easy and useful.\par \par 
alien:~$ echo $[ 4 * 2 ]\par 8\par alien:~$\par \par or another example:\par 
\par alien:~$ echo $[ 10 + 5 ]\par 15\par alien:~$\par \par Easy ? .... I think 
it is =)\par \par The internal calculator can also be used like this: \par \par 
alien:~$ echo $(( 10 + 5 ))\par 15\par alien:~$\par \par The second way of using 
the internal shell calculator is here just\par so you dont get confused if you 
see it used that way sometime.\par \par 
--------------------------------------------------------------------------------\par 
\par Now I'd like to show the *string comparing* with "if" statements,\par which 
can be a little hard at first contact, but as soon as you get\par familiar with 
it, it wont be any problems.\par So here's an example.\par \par 
--------------------------------------------------------------------------------\par 
\par #!/bin/bash\par \par echo -n "enter a name: "\par read var1\par echo -n 
"enter another name: "\par read var2\par \par if [ "$var1" = "$var2" ]; then\par 
echo "The names are the same"\par else\par echo "The names were not the 
same"\par fi\par \par exit 0\par \par \par 
--------------------------------------------------------------------------------\par 
\par Note: "fi" is the ending of if, just like a "\}" is the ending of a 
"\{",\par exit 0 terminates the script correctly and returns you to the 
prompt.\par \par Another note is that instead of '=' you can use '-eq' to test 
if\par 2 expressions are equal, or '-eg' to check if 2 integers are equal, 
etc.\par \par It should also be said that a variable say '$var' can be written 
\par as this: $\{var\}, just so you know if you see it done that way\par in some 
scripts, but here we will use the $var way.\par \par 
--------------------------------------------------------------------------------\par 
\par This example if executed looks like this:\par \