The Bash Shell
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Guide to (mostly) Harmless Hacking
Vol. 5 Programmers' Series
No. 4: A nice 'n' easy introduction into the bash shell
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By idle (idle@mailexcite.com)
with a little help from his friends (Meino :) (Carolyn Meinel)
The first in the Programmers' Series introduced you
to some of the very
basics of writing shell scripts. Creating files, executing commands
and so
on. This Guide will introduce you to additional important
concepts, but
this time using the bash shell.
Why is shell programming important for hacking?
Let's say you are trying
to get root control of a Hacker Wargame computer (see
http://www.happyhacker.org
for latest information on what computers are
legal to break into). You find an exploit shell script
at some place such
as http://www.rootshell.com
that looks ideal for doing the job -- but it
doesn't work! Maybe your problem was not with the exploit
script, but with what shell you are using or how your shell is
set up. This Guide will help you understand more about
what makes the bash shell work and how to make it do what you
want it to do.
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In this Guide you will learn about:
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Newbie note: Bash is a Unix shell program. It takes all
your commands and turns them into something a Unix type operating
system can understand. I (Carolyn Meinel) recommend the
tcsh shell, but if you can't use tcsh right now, bash is my second
favorite shell. Bash stands for "Bourne Again Shell,"
a word play on the Bourne Shell, from which the bash shell was
adapted. To find out whether you are currently using the
bash shell, in your shell account give the command "env".
It will include an entry "SHELL:bash" if you are already
using it. If it shows a different shell, give the
command "bash". If it gives an error message,
you don't have ash.
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You'll soon see that even your most basic shell in
any kind of Unix is more powerful than DOS, and if you are short
of ideas for scripts to write, hopefully this will open your
mind a little.
More on the bash shell --->>
