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LINUX SHELLCOMPSYS202 / MECHENG270

Wednesday, 20 July 2011

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Contents

Where can I get Linux?

Where can I get help with Linux?

What is the Linux shell ?

How do I use the Linux shell ?


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Where Linux?

Linux is installed in most SE, CS, ECE, andEngineering Faculty labs. You generally need to rebootand choose Linux from a boot menu.

Linux is Free/Open Source software, so you canlega!y

copy it from friends and install it at home.


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Where Linux?

You can download Linux for free, or you can buy it.

http://www.ubuntulinux.org/

Dick Smith Electronics sells CDs.

There are CD images available on the UofA network ifyouwant to burn a CD.

http://www.ubuntulinux.org/http://www.ubuntulinux.org/http://www.ubuntulinux.org/

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Linux Help?

We will be covering Linux usage in some lectures.

TAs are available to help in labs.

Reference guides and documentation will be made

available via. Cecil.


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Linux Help?

There is avast collection of information on the

Internet.

http://www.linux.org/

http://www.ubuntulinux.org/

http://www.wikipedia.com/

http://www.wikipedia.com/http://www.ubuntulinux.org/http://www.linux.org/http://www.wikipedia.com/http://www.wikipedia.com/http://www.ubuntulinux.org/http://www.ubuntulinux.org/http://www.linux.org/http://www.linux.org/

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Which Linux

There are many flavours of Linux available. eg.

Redhat, Ubuntu, Fedora, Gentoo.

We will be using Ubuntu Linux

When searching the Internet, make sure you find

recent help. Articles from 1996 may not be relevantnow, for example.


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Remember

command options arguments


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File Tree

ccog001

Desktop example

example.jpg example.c


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File Naming

Linux is case sensitive.

This means that:

he!o.jpgis NOT the same file asHELLO.JPG


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File Naming

Filenames can contain spaces, but this is awkward for

the command line.

For now, dont put spaces in filenames.

You can use underscores if you want.

eg. My_simple_program.cpp


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Working Directory

Every program running is in a specific directory- the

current directory

This is the place it looks for files, or will save files to, bydefault.

We can move a program to a different directory.


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Starting Directory

When we first log in, our desktop (file manager) will bein our Desktop directory.

If we start a terminal from the menu, it will be in our

HOME directory.


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Navigation

cd

change directory

Navigate to other locations in the filesystem


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pwd

pwdprint working directory

Shows the name of the folder that the terminal is

currently in.


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ls

ls

list - Show files in the current directory.


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mv

mv

move files.

This will move a file to a different location.

It can also rename files.


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cp

cp

copy files.

Make a copy of files.

eg. cp labex1.c labex1.c.backup


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echo

echo

echo some text back to us

This will display some text to the output.

eg. echo hello there


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cat

cat

catalog - Reads a file and sends it to output.


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more

moreshow us more of a file.

This will read a file and display it to our terminal, but

will pause once it fills the screen until we press space.


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cut

cutTakes the input text and, for each line, removes someof it.

eg. ls -l | cut -c29-34


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Combining Commands

in UNIX systems, most commands are considered tobe building blocks. You use them to construct moresophisticated operations.


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Pipe

|takes the output from one command and feeds it intothe next.

ls | more


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Backticks

`

If we put a command inside backticks ``, the shell willrun that command first, thenreplacethe `` part withthe output of that command.

echo My working dir is `pwd`


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More Backticks

We can put multiple commands inside backticks:

echo The largest file is `ls -l | sort -n -k 5 | tail -1 | cut -c54-`


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Sequencing

Like many programming languages, we can specify asequence of commands, separated by the ; character.

echo my files: ; ls

The second command wont start until the first finishes


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Typing Shortcuts

The shell contains features to help us with our typing.

We can use the arrow keys to go back through previouscommands.


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Auto Completion

The shell can try and work out what we meant bywhat weve typed so far.

If it can, it will complete as much as it can for you.

Press to do this.

Press twice and the shell will suggest what

matches so far.


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Build Your Own

Except for a very few built-in commands, all shell

commands are just programs.

You can write your own.

Most common ones included on the system are in the /

usr/bin directory.


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Explore

Have a look around the system, find new commands,figure out what they do.


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Compiling

Linux comes with a C/C++ compiler, called GCC.

GCC is a free software compiler and is very crossplatform. see: http://www.gnu.org/

We can call it from the UNIX shell using the g++command.

g++ -o targetsource.cpp


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Running programs

To run a program we must type its name.

The shell will search our path for a program with

that name, and if it finds it, it will run it.echo $PATH

our home directory is not by default in the path,

so we have to specify where the program is../myprogram

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