1 About this document
This is a collection of good introductions into using the Linux or unix command
line. They are changed and editied slightly from there web counter
parts, feel free to use the orginals as provided via the links.
Note that Copyright permission was recieced to produce this for the course
from the different sources.
2 Quick Intro Into Linux
This is from http://members.toast.net/art.ross/Linux\_2003/Linux\_Newbie\
_Manual/part1/command1.html
Welcome to Super-DOS!
That thing that looks like MS-DOS is a Linux terminal (sometimes called a
"console"). Iťs here that all Linux commands are entered. If you're familiar
with DOS, then get ready for Super-DOS!
3 The BASH shell
Other shells are available, but BASH, the Bourne Again Shell, is the Linux
default. It incorporates features of its namesake, the Bourne shell, and those
of the Korn, C and TCSH shells.
The BASH built-in command history remembers the last 500 commands
entered by default. They can be viewed by entering history at the command
prompt. A specific command is retrieved by pressing the UP ARROW or
DOWN ARROW at the command prompt.
3.1 Guide to Linux File Command Mastery
By Sheryl Calish http://www.oracle.com/technology/pub/articles/calish\
_file\_commands.html A crash course in Linux file commands for the newly
initiated
Although GUI desktops such as KDE and GNOME help users take advan-
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tage of Linux features without functional knowledge of the command-line
interface, more power and flexibility are often required. Moreover, a basic
familiarity with these commands is still essential to properly automate
certain functions in a shell script.
This article is a "crash course" in Linux file commands for those who are either
new to the operating system or simply in need of a refresher. It includes
a brief overview of the more useful commands as well as guidance regarding
their most powerful applications. Combined with a little experimentation,
the information included here should lead to an easy mastery of these essential
commands. (Note: When a kernel tweaked with Oracle Cluster File
System (OCFS2) is involved, some of these commands may behave somewhat
differently. In that case, Oracle provides an OCFS2 toolset that can be a
better alternative for file command purposes.)
Note that all the included examples were tested on SUSE Linux 8.0 Professional.
While there is no reason to believe they will not work on other
systems, you should check your documentation for possible variations if problems
arise.
3.2 Background Concepts
Before delving into specifics, leťs review some basics.
3.2.1 Files and Commands
Everything is treated as a file in the Linux/UNIX operating system: hardware
devices, including the keyboard and the terminal, directories, the commands
themselves and, of course, files. This curious convention is, in fact, the basis
for the power and flexibility of Linux/UNIX.
Most commands, with few variations, take the form:
command [option] [source file(s)] [target file]
3.2.2 Getting Help
Among the most useful commands, especially for those learning Linux, are
those that provide help. Two important sources of information in Linux are
the on-line reference manuals, or man pages, and the whatis facility. You
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can access an unfamiliar commanďs man page description with the whatis
command.
whatis echo
To learn more about that command use:
man echo
If you do not know the command needed for a specific task, you can generate
possibilities using man -k, also known as apropos, and a topic. For example:
man -k files
One useful but often-overlooked command provides information about using
man itself:
man man
You can scroll through any man page using the SPACEBAR; the UP ARROW
will scroll backward through the file. To quit, enter q,!, or CTRL-Z.
4 Using info, the Documentation Tools
http://www.linuxtopia.org/online\_books/centos\_linux\_guides/centos\
_linux\_developer\_tools\_guide/s1-using-info.html
info provides the sources for documentation for the GNU tools.
4.1 Reading info Documentation
Browse through the documentation using either Emacs1
or the info documentation
browser program. The information is in nodes, which correspond
to the sections of a printed book. Follow them in sequence, as in books, or,
using the hyperlinks, find the node that has the information you need. info
has hot references (if one section refers to another section, info takes you
directly to that other section, but gives you the ability to return easily. You
can also search for particular words or phrases. Use info by typing its name
at a shell prompt; no options or arguments are necessary. Check that info is
in your shell path. If you have problems running info, contact your system
administrator.
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The best or worst text editor to ever be created. Depending on your point of view
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To get help with using info, type h for a programmed instruction sequence,
or [Ctrl]-[h] for a short summary of commands. To stop using info, type [q].
4.2 About Paths
Whenever I mention a path, I'm speaking about the route taken to get to a
file or directory. (Don't confuse this with PATH which is an "environment
variable" - discussed later.)
One thing I should mention - to prevent confusion - is that drive letters don't
exist in Linux. There is no A:, C: or D:, only the root directory (/), which
contains everything else. You'll also notice that the backslash (\) is never
used in Linux, only the forward-slash (/).
4.3 Absolute And Relative Paths
A relative path means just that, relative to the current directory. You can
always tell a relative path because it never starts with a /. If you were in /etc
and wanted to move to the directory /etc/defaults then instead of entering
the absolute path:
cd /etc/defaults
...iťs quicker just to enter the relative path:
cd defaults
Ok, now that you have some fundamental knowledge of paths, iťs time to
learn the two most important commands, cd and ls.
4.4 cd - change directory
4.4.1 Examples
cd
Move to home directory of the account you're logged into, e.g. /home/guest.
cd -
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Move back to previous directory you were in.
cd ..
Move up to the parent directory, i.e. the directory that holds the directory
you're currently in.
cd /usr/docs
Move to the directory docs, which is contained in the directory usr, which
like everything else, is contained in the root directory (/).
cd reports
Move to the directory reports, contained in the directory you're currently in.
4.5 ls - list [a directory ]
4.5.1 Examples
ls
Display the contents of the directory you're currently in.
ls -a
Display every file and directory in the current directory (i.e. including "hidden"
files and directories).
ls -l
Display the files in the current directory, including (from left to right): the
file type; permissions; the number of hard links; the owner name; the group
name; the size in bytes; and the date the file was last saved.
To combine the above two examples you would enter:ls -al
ls | less
Pipe (pass) the listing of the current directory to the less program, allowing
you to scroll up and down a long listing. (That -- character is called a
"pipe".)
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4.6 Less Keys:
Down cursor = Down 1 line.
Up cursor = Up 1 line.
Spacebar = Down 1 screen.
b = Back up 1 screen.
q = Quit.
h = Activate help screen.
ls -l /usr | less
Pipe the listing of the /usr directory (passing all file details (-l)), to the less
program.
ls > list.of.files
Either create or overwrite the file list.of.files, with a redirected () listing
of the current directory, as the file's content.
ls >> list.of.files
The same as above, except this time the listing is appended to the end of the
file list.of.files.
5 Making and Removing Directories
This is from http://members.toast.net/art.ross/Linux\_2003/Linux\_Newbie\
_Manual/part1/command2.html Learn by doing is the nature of this manual,
and in keeping with that belief, here's a tutorial to teach you the mkdir and
rmdir commands, to make and remove directories.
Rather than entering a tedious:
cd (Only required if you're not in your home directory.)
mkdir a
mkdir a/sub
mkdir a/sub/subsub
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...simply enter:
cd; mkdir a a/sub a/sub/subsub
Note
Here you've just been introduced to a nice trick - using the semi-colon (;) to
enter multiple commands in one go. This will work with anything you can
think of (even aliases!).
To check that everything is, as it should be, enter:
tree a
...to display the following:
a
`-- sub
`-- subsub
2 directories, 0 files
Now that the three directories have been created, iťs time to destroy them!
Enter:
rmdir a
5.1 Some Things You Can't Do
To prevent accidents, rmdir will refuse to remove directories that contains
files and/or other directories. Which is why you received the error message:
rmdir: a: Directory not empty
This will also prevent you removing a parent directory, since by its very name,
ithas to contain your current working directory. Logic also dictates that you
can't remove your current directory since this would involve you being lost
in limbo'!
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The rmdir has a handly little option, called -p. Iťs purpose is to ask the
shell to not only remove a directory, but also all of its parent directories - so
long as each parent is empty.
Enter:
rmdir -p a/sub
...oh dear, still an annoying error message:
rmdir: a/sub: Directory not empty
Now press the up cursor key to bring back up the last command, but this
time add /subsub before pressing the Return key, like so:
rmdir -p a/sub/subsub
Bingo, all three directories have been removed!
6 Copy move and remove files
This is from http://members.toast.net/art.ross/Linux\_2003/Linux\_Newbie\
_Manual/part1/command3.html
6.1 cp - copy
6.1.1 Examples
cp -r a b
Copy the entire contents of directory a into directory b.
cp a.txt backup
Copy the file a.txt across to the directory backup.
cp a.txt backup/a bk.txt
Copy the file a.txt across to the directory backup and rename it a bk.txt
at the same time. If the file backup/a bk.txt already existed then it will be
overwritten without warning.
cp -i a.txt backup/a bk.txt
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The same as above but asks for confirmation before overwriting an existing
file.
cp a b c d
In the above form, every parameter but the last - are the files to copy, and
the last parameter - is the directory to copy the files to.
6.1.2 Note
When copying more than one file you can't rename it at the same time.
6.2 mv - move
mv is a clever little command that will either move a file (mv file directory),
or rename it (mv oldfilename newfilename).
mv a b c work/reports
Move the files a, b, and c into the directory work/reports.
mv -i a b c work/reports
The same as above, but asks for confirmation before overwriting any existing
files.
mv a.txt b.txt
Rename the file a.txt - b.txt.
6.3 rm - remove
rm a b c
Remove the files a, b and c.
rm -i a b c
The same as above, but asks for confirmation before removing each file - very
important when removing files using wildcards!
rm -r work/reports
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Ther stands for "recursive" meaning every file and directory, in the directory
work/reports will be removed,without warning - so be careful!
7 Viewing and Searching
http://unix.cms.gre.ac.uk/general/viewing.html
7.0.1 Note:
These tutorials assume you have a copy of the tutorial.txt file which can be
copied from:
/home/wug01/public html/general/tutorial.txt
Or alternatively, it can be downloaded from http://unix.cms.gre.ac.uk/
general/tutorial.txt and saved in your home area. (Right click and Save
As)
7.0.2 cat (concatenate)
The command cat can be used to display the contents of a file on the screen.
Type:
cat tutorial.txt
As you can see, the file is longer than than the size of the window, so it scrolls
past making it unreadable.
7.0.3 less
The command less writes the contents of a file onto the screen a page at a
time. Type:
less tutorial.txt
Press the space-bar if you want to see another page, type q if you want to
quit reading. As you can see, less is used in preference to cat for long files.
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7.0.4 head
The head command writes the first ten lines of a file to the screen.
First clear the screen then type:
head tutorial.txt
Then type:
head -5 tutorial.txt
What difference did the -5 do to the head command?
7.0.5 tail
The tail command writes the last ten lines of a file to the screen.
Clear the screen and type:
tail tutorial.txt
How can you view the last 15 lines of the file?
7.0.6 Simple searching using less
Using less, you can search though a text file for a keyword (pattern). For
example, to search through tutorial.txt for the word tutorial, type:
less tutorial.txt
then, still in less (i.e. don't press q to quit), type a slash followed by the
word to search
/tutorial
As you can see, /tutorial finds and highlights the keyword. Type n to
search for the next occurrence of the word.
7.0.7 grep
grep is one of many standard UNIX utilities. It searches files for specified
words or patterns. First clear the screen, then type:
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grep tutorial tutorial.txt
As you can see, grep has printed out each line containing the word tutorial.
Or has it????
Try typing:
grep tutorial tutorial.txt
The grep command is "case sensitive"; it distinguishes between tutorial and
Tutorial. To ignore upper/lower case distinctions, use the -i option, i.e.
type:
grep -i tutorial tutorial.txt
To search for a phrase or pattern, you must enclose it in single quotes (the
apostrophe symbol). For example to search for spinning top, type:
grep -i 'spinning top' tutorial.txt
Some of the other options of grep are:
-v display those lines that do NOT match
-n precede each matching line with the line number
-c print only the total count of matched lines
Try some of them and see the different results. Don't forget, you can use
more than one option at a time, for example, the number of lines without
the words tutorial or Tutorial is:
grep -ivc tutorial tutorial.txt
7.0.8 wc
wc (word count)
A handy little utility is the wc command, short for word count. To do a word
count on tutorial.txt, type:
wc -w tutorial.txt
To find out how many lines the file has, type:
wc -l tutorial.txt
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7.0.9 Summary:
cat file display a file
more file display a file a page at a time
head file display the first few lines of a file
tail file display the last few lines of a file
grep 'keyworď file search a file for keywords
wc file count number of lines/words/characters in file
8 Further Reading:
I will eventually get these good documents incorprated into this document.
But at this stage they will remain links:
Here is a good intro into regular expresions, sed and and find:
http://www.grymoire.com/Unix/Regular.html
http://www.grymoire.com/Unix/Sed.html
http://www.grymoire.com/Unix/Find.html
Note that they are old, but I have run through them myself and all work fine
on linux.
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