This document discusses the Bourne-Again Shell (bash) and basic navigation commands. It introduces bash as the default shell on Linux systems and explains that bash commands are built-in rather than existing as separate files. Examples of basic navigation commands like cd, pwd, and relative/absolute paths are provided. The document encourages practice of these fundamental commands and lists resources for learning more about bash.

1. The Shell Game 3
Kevin O'Brien
Washtenaw Linux Users Group
http://www.lugwash.org

2. The Bourne-Again Shell (bash)
● Now that we have looked at some general
ideas about shells, and looked at the choices
that are available, it is time to focus on the shell
we will use for the rest of the series
● The Bourne-Again Shell (bash) is the default on
all Linux systems
● It is as universal as anything can be in the
world of Unix-like systems
● So if you only learn one shell, this is the one to
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learn

3. Bash commands
● Most Linux commands are separate files
● You can find them by name on your hard drive
● You can open a man page for them
● But bash commands are all internal to bash
● You cannot find them on your hard drive
● They do not have a man page
● Instead, they are all in the man page for bash
3

4. Examples
Just some of the bash commands
alias bind cd dirs
echo eval exec exit
hash help history jobs
kill logout pwd read
set source suspend times
trap type umask wait
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5. Navigating
● A good starting point for bash is learning to
move around
● This is done with the cd command
● Did you note that cd is one of the built-in
commands in bash?
● That means the information about it is in the
bash man page
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6. Cd 1
● This stands for Change Directory
● More precisely, it should be Change the
Current Working Directory
● This is often the most convenient way to
execute other commands, even if they could
be done some other way
● For example, you could change the working
directory so that you could then work on a file
in that directory 6

7. Cd 2
● The syntax for this command is
cd [option] [directory]
● The arguments in brackets are themselves
optional, i.e., you can successfully execute the
command without specifying either an option
or a directory
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8. Shortcuts
● In Unix-like operating systems the current
directory can be represented by a dot
● The parent directory is represented by two
dots
● The home directory is represented by ~ (called
a tilde, found in the upper left of the keyboard)
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9. Cd options
● There are only two, and they are not
commonly used (-P, -L)
● These involve either following or not not
following symbolic links
● So we won't discuss them further at this time
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10. Absolute paths
● These are paths that begin with the root (/) of
the system
● An example might be /home/kevin/Downloads,
which is where all of my downloaded files go
● Relative paths are paths relative to the current
working directory
● So, if I had a sub-directory of my Downloads
directory, for example Firefox, I could give it the
relative path /Firefox if I am in my Downloads10
directory

11. Present Working Directory
● The directory you are currently in is also
known as the Present Working Directory
● The command to display this is pwd
● Did you notice this is also a built-in bash
command?
● This means you can find more info about it in
the bash man page
● You may not need this as much if your bash
prompt displays the current directory 11

12. Exercises 1
● First, use the pwd command to display your
Present Working Directory
● To go to /usr/local/share, type
cd /usr/local/share
● To go to your home directory, type
cd ~
● To go back to /usr/local/share, type
cd
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13. Exercises 2
● To go to /usr/local/share/man type
cd /man
● To go back to /usr/local/share, type
cd ..
● To go the the root of the system, type
cd /
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14. Practice these commands
● To be really proficient you need to have these
commands memorized
● They are not all that complicated
● Navigation is so essential that you don't want
to be stopping to try and look up how to
navigate when you are fixing a problem
● How do you get to Carnegie Hall?
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15. Resources
● The bash man page (you can also read this
online at http://linux.die.net/man/1/bash)
● The Bash Reference Manual at
http://www.gnu.org/software/bash/manual/bas
href.html
● You have man pages on your computer, and
they are there even if you are not connected
to the Internet. So get to know how to use the
man pages that are already on your hard 15
drive.