UNIX Tutorial One
Listing files and directories
ls (list)
When you first login,
your current working directory is your home directory. Your home directory has
the same name as your user-name, for example, ee91ab, and it is where your
personal files and subdirectories are saved.
To find out what is in
your home directory, type
% ls (short for list)
The ls command lists the
contents of your current working directory.
There may be no files visible
in your home directory, in which case, the UNIX prompt will be returned.
Alternatively, there may already be some files inserted by the System
Administrator when your account was created.
ls does not, in fact, cause all the files in your
home directory to be listed, but only those ones whose name does not begin with
a dot (.) Files beginning with a dot (.) are known as hidden files and usually
contain important program configuration information. They are hidden because
you should not change them unless you are very familiar with UNIX!!!
To list all files in
your home directory including those whose names begin with a dot, type
% ls -a
ls is an example of a command which can take
options: -a is an example of an option. The options change
the behaviour of the command. There are online manual pages that tell you which
options a particular command can take, and how each option modifies the
behaviour of the command. (See later in this tutorial)
1.2 Making Directories
mkdir (make directory)
We will now make a subdirectory in your home directory to
hold the files you will be creating and using in the course of this tutorial.
To make a subdirectory called unixstuff in your current working
directory type
% mkdir unixstuff
To see the directory you have just created, type
% ls
1.3 Changing to a different directory
cd (change directory)
The command cd directory means change the
current working directory to 'directory'. The current working directory may be
thought of as the directory you are in, i.e. your current position in the
file-system tree.
To change to the directory you have just made, type
% cd unixstuff
Type ls to see the contents (which should be empty)
Exercise 1a
Make another directory inside the unixstuff directory
called backups
1.4 The directories . and ..
Still in the unixstuff directory, type
% ls -a
As you can see, in the unixstuff directory (and in all
other directories), there are two special directories called (.) and (..)
In UNIX, (.) means the current directory, so typing
% cd .
NOTE: there is a space between cd and the dot
means stay where you are (the unixstuff
directory).
This may not seem very useful at first, but using (.)
as the name of the current directory will save a lot of typing, as we shall see
later in the tutorial.
(..) means the parent of the current directory, so
typing
% cd ..
will take you one directory up the hierarchy (back to your
home directory). Try it now.
Note: typing cd with no argument always returns you to
your home directory. This is very useful if you are lost in the file system.
1.5 Pathnames
pwd (print working directory)
Pathnames enable you to work out where you are in relation to
the whole file-system. For example, to find out the absolute pathname of your
home-directory, type cd to get back to your home-directory and then type
% pwd
The full pathname will look something like this -
/a/fservb/fservb/fservb22/eebeng99/ee91ab
which means that ee91ab (your home directory) is in
the directory eebeng99 (the group directory),which is located on the fservb
file-server.
Note:
/a/fservb/fservb/fservb22/eebeng99/ee91ab
can be shortened to
/user/eebeng99/ee91ab
Exercise 1b
Use the commands ls, pwd and cd
to explore the file system.
(Remember, if you get lost, type cd by itself to return
to your home-directory)
1.6 More about home directories and pathnames
Understanding pathnames
First type cd to get back to your home-directory, then
type
% ls unixstuff
to list the conents of your unixstuff directory.
Now type
% ls backups
You will get a message like this -
backups: No such file or directory
The reason is, backups is not in your current working
directory. To use a command on a file (or directory) not in the current working
directory (the directory you are currently in), you must either cd to
the correct directory, or specify its full pathname. To list the contents of
your backups directory, you must type
% ls unixstuff/backups
~ (your home directory)
Home directories can also be referred to by the tilde ~
character. It can be used to specify paths starting at your home directory. So
typing
% ls ~/unixstuff
will list the contents of your unixstuff directory, no matter
where you currently are in the file system.
What do you think
% ls ~
would list?
What do you think
% ls ~/..
would list?
Summary
|
ls
|
list files and directories
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|
ls -a
|
list all files and directories
|
|
mkdir
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make a directory
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|
cd directory
|
change to named directory
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|
cd
|
change to home-directory
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cd ~
|
change to home-directory
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cd ..
|
change to parent directory
|
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pwd
|
display the path of the current directory
|
UNIX Tutorial Two
2.1 Copying Files
cp (copy)
cp file1 file2 is the command which makes a copy of
file1 in the current working directory and calls it file2
What we are going to do now, is to take a file stored
in an open access area of the file system, and use the cp command to
copy it to your unixstuff directory.
First, cd to your unixstuff directory.
% cd ~/unixstuff
Then at the UNIX prompt, type,
% cp /vol/examples/tutorial/science.txt .
(Note: Don't forget the dot (.) at the end. Remember,
in UNIX, the dot means the current directory.)
The above command means copy the file science.txt
to the current directory, keeping the name the same.
(Note: The directory /vol/examples/tutorial/ is
an area to which everyone in the department has read and copy access. If you
are from outside the University, you can grab a copy of the file here. Use 'File/Save As..' from the menu
bar to save it into your unixstuff directory.)
Exercise 2a
Create a backup of your science.txt file by copying it
to a file called science.bak
2.2 Moving files
mv (move)
mv file1 file2 moves (or renames) file1 to file2
To move a file from one place to another, use the mv
command. This has the effect of moving rather than copying the file, so you end
up with only one file rather than two.
It can also be used to rename a file, by moving the
file to the same directory, but giving it a different name.
We are now going to move the file science.bak to your
backup directory.
First, change directories to your unixstuff directory
(can you remember how?). Then, inside the unixstuff directory, type
% mv science.bak backups/.
Type ls and ls backups to see if it has worked.
2.3 Removing files and directories
rm (remove), rmdir (remove directory)
To delete (remove) a file, use the rm command. As an
example, we are going to create a copy of the science.txt file then
delete it.
Inside your unixstuff directory, type
% cp science.txt tempfile.txt
% ls (to check if it has created the file)
% rm tempfile.txt
% ls (to check if it has deleted the file)
% ls (to check if it has created the file)
% rm tempfile.txt
% ls (to check if it has deleted the file)
You can use the rmdir command to remove a
directory (make sure it is empty first). Try to remove the backups
directory. You will not be able to since UNIX will not let you remove a
non-empty directory.
Exercise 2b
Create a directory called tempstuff using mkdir
, then remove it using the rmdir command.
2.4 Displaying the contents of a file on the screen
clear (clear screen)
Before you start the next section, you may like to clear the
terminal window of the previous commands so the output of the following
commands can be clearly understood.
At the prompt, type
% clear
This will clear all text and leave you with the % prompt at
the top of the window.
cat (concatenate)
The command cat can be used to display the contents of
a file on the screen. Type:
% cat science.txt
As you can see, the file is longer than than the size of the
window, so it scrolls past making it unreadable.
less
The command less writes the contents of a file onto
the screen a page at a time. Type
% less science.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.
head
The head command writes the first ten lines of a file
to the screen.
First clear the screen then type
% head science.txt
Then type
% head -5 science.txt
What difference did the -5 do to the head command?
tail
The tail command writes the last ten lines of a file
to the screen.
Clear the screen and type
% tail science.txt
How can you view the last 15 lines of the file?
2.5 Searching the contents of a file
Simple searching using less
Using less, you can search though a text file for a
keyword (pattern). For example, to search through science.txt for the
word 'science', type
% less science.txt
then, still in less (i.e. don't press [q] to quit),
type a forward slash [/] followed by the word to search
/science
As you can see, less finds and highlights the
keyword. Type [n] to search for the next occurrence of the word.
grep (don't ask why it is called grep)
grep is one of many standard UNIX utilities. It searches files
for specified words or patterns. First clear the screen, then type
% grep science science.txt
As you can see, grep has printed out each line
containg the word science.
Or has it????
Try typing
% grep Science science.txt
The grep command is case sensitive; it
distinguishes between Science and science.
To ignore upper/lower case distinctions, use the -i option,
i.e. type
% grep -i science science.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' science.txt
Some of the other options of grep are:
-v display those lines that do NOT match
-n precede each maching line with the line number
-c print only the total count of matched lines
-n precede each maching 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 science or Science is
% grep -ivc science science.txt
wc (word count)
A handy little utility is the wc command, short for
word count. To do a word count on science.txt, type
% wc -w science.txt
To find out how many lines the file has, type
% wc -l science.txt
Summary
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cp file1 file2
|
copy file1 and call it file2
|
|
mv file1 file2
|
move or rename file1 to file2
|
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rm file
|
remove a file
|
|
rmdir directory
|
remove a directory
|
|
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
|
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tail file
|
display the last few lines of a file
|
|
grep 'keyword' file
|
search a file for keywords
|
|
wc file
|
count number of lines/words/characters in file
|
UNIX Tutorial Three
3.1 Redirection
Most processes initiated
by UNIX commands write to the standard output (that is, they write to the
terminal screen), and many take their input from the standard input (that is,
they read it from the keyboard). There is also the standard error, where
processes write their error messages, by default, to the terminal screen.
We have already seen one
use of the cat command to write the contents of a file to the
screen.
Now type cat without specifing a
file to read
% cat
Then type a few words on
the keyboard and press the [Return] key.
Finally hold the [Ctrl] key down and press [d] (written as ^D for
short) to end the input.
What has happened?
If you run the cat command without
specifing a file to read, it reads the standard input (the keyboard), and on
receiving the'end of file' (^D), copies it to the standard output (the screen).
In UNIX, we can redirect
both the input and the output of commands.
3.2 Redirecting the Output
We use the > symbol
to redirect the output of a command. For example, to create a file called list1
containing a list of fruit, type
% cat > list1
Then type in the names
of some fruit. Press [Return] after each one.
pear
banana
apple
^D (Control D to stop)
banana
apple
^D (Control D to stop)
What happens is the cat command reads the
standard input (the keyboard) and the > redirects the output, which normally
goes to the screen, into a file called list1
To read the contents of
the file, type
% cat list1
Using the above method,
create another file called list2 containing the following fruit: orange,
plum, mango, grapefruit. Read the contents of list2
The form >>
appends standard output to a file. So to add more items to the file list1,
type
% cat >> list1
Then type in the names
of more fruit
peach
grape
orange
^D (Control D to stop)
grape
orange
^D (Control D to stop)
To read the contents of
the file, type
% cat list1
You should now have two
files. One contains six fruit, the other contains four fruit. We will now use
the cat command to join (concatenate) list1 and list2
into a new file called biglist. Type
% cat list1 list2 > biglist
What this is doing is
reading the contents of list1 and list2 in turn, then outputing
the text to the file biglist
To read the contents of
the new file, type
% cat biglist
3.3 Redirecting the Input
We use the < symbol
to redirect the input of a command.
The command sort alphabetically or
numerically sorts a list. Type
% sort
Then type in the names
of some vegetables. Press [Return] after each one.
carrot
beetroot
artichoke
^D (control d to stop)
beetroot
artichoke
^D (control d to stop)
The output will be
artichoke
beetroot
carrot
beetroot
carrot
Using < you can
redirect the input to come from a file rather than the keyboard. For example,
to sort the list of fruit, type
% sort < biglist
and the sorted list will
be output to the screen.
To output the sorted
list to a file, type,
% sort < biglist > slist
Use cat to read the contents of
the file slist
3.4 Pipes
To see who is on the
system with you, type
% who
One method to get a
sorted list of names is to type,
% who > names.txt
% sort < names.txt
% sort < names.txt
This is a bit slow and
you have to remember to remove the temporary file called names when you have
finished. What you really want to do is connect the output of the who command directly to the
input of the sort command. This is exactly what pipes do. The
symbol for a pipe is the vertical bar |
For example, typing
% who | sort
will give the same
result as above, but quicker and cleaner.
To find out how many
users are logged on, type
% who | wc -l
a2ps -Phockney textfile is the command to print
a postscript file to the printer hockney.
Using pipes, print all
lines of list1 and list2 containing the letter 'p', sort the
result, and print to the printer hockney.
|
command > file
|
redirect
standard output to a file
|
|
command >> file
|
append
standard output to a file
|
|
command < file
|
redirect
standard input from a file
|
|
command1 | command2
|
pipe
the output of command1 to the input of command2
|
|
cat file1 file2 > file0
|
concatenate
file1 and file2 to file0
|
|
sort
|
sort
data
|
|
who
|
list
users currently logged in
|
|
a2ps -Pprinter textfile
|
print
text file to named printer
|
|
lpr -Pprinter psfile
|
print
postscript file to named printer
|
UNIX Tutorial Four
4.1 Wildcards
The characters * and ?
The character * is
called a wildcard, and will match against none or more character(s) in a file
(or directory) name. For example, in your unixstuff directory, type
% ls list*
This will list all files
in the current directory starting with list....
Try typing
% ls *list
This will list all files
in the current directory ending with ....list
The character ? will
match exactly one character.
So ls ?ouse will match files like house and mouse, but not grouse.
Try typing
So ls ?ouse will match files like house and mouse, but not grouse.
Try typing
% ls ?list
4.2 Filename conventions
We should note here that
a directory is merely a special type of file. So the rules and conventions for
naming files apply also to directories.
In naming files,
characters with special meanings such as / * & % , should be
avoided. Also, avoid using spaces within names. The safest way to name a file
is to use only alphanumeric characters, that is, letters and numbers, together
with _ (underscore) and . (dot).
File names
conventionally start with a lower-case letter, and may end with a dot followed
by a group of letters indicating the contents of the file. For example, all
files consisting of C code may be named with the ending .c, for example,
prog1.c . Then in order to list all files containing C code in your home
directory, you need only type ls
*.c in that directory.
Beware: some applications give the same name to all the output files
they generate.
For example, some compilers, unless given the appropriate option, produce compiled files named a.out. Should you forget to use that option, you are advised to rename the compiled file immediately, otherwise the next such file will overwrite it and it will be lost.
For example, some compilers, unless given the appropriate option, produce compiled files named a.out. Should you forget to use that option, you are advised to rename the compiled file immediately, otherwise the next such file will overwrite it and it will be lost.
4.3 Getting Help
On-line Manuals
There are on-line
manuals which gives information about most commands. The manual pages tell you
which options a particular command can take, and how each option modifies the
behaviour of the command. Type man command to read the manual page for a
particular command.
For example, to find out
more about the wc (word count) command, type
% man wc
Alternatively
% whatis wc
gives a one-line
description of the command, but omits any information about options etc.
Apropos
When you are not sure of
the exact name of a command,
% apropos keyword
will give you the
commands with keyword in their manual page header. For example, try typing
% apropos copy
|
*
|
match
any number of characters
|
|
?
|
match
one character
|
|
man command
|
read
the online manual page for a command
|
|
whatis command
|
brief
description of a command
|
|
apropos keyword
|
match
commands with keyword in their man pages
|
UNIX Tutorial Five
5.1 File system security (access rights)
In your unixstuff
directory, type
% ls -l (l for long listing!)
You will see that you
now get lots of details about the contents of your directory, similar to the
example below.
Each file (and
directory) has associated access rights, which may be found by typing ls -l. Also, ls -lg gives additional
information as to which group owns the file (beng95 in the following example):
-rwxrw-r-- 1 ee51ab beng95 2450 Sept29 11:52 file1
In the left-hand column
is a 10 symbol string consisting of the symbols d, r, w, x, -, and,
occasionally, s or S. If d is present, it will be at the left hand end of the
string, and indicates a directory: otherwise - will be the starting symbol of
the string.
The 9 remaining symbols
indicate the permissions, or access rights, and are taken as three groups of 3.
·
The left group of 3 gives the file
permissions for the user that owns the file (or directory) (ee51ab in the above
example);
·
the middle group gives the
permissions for the group of people to whom the file (or directory) belongs
(eebeng95 in the above example);
·
the rightmost group gives the
permissions for all others.
The symbols r, w, etc.,
have slightly different meanings depending on whether they refer to a simple
file or to a directory.
·
r (or -), indicates read permission
(or otherwise), that is, the presence or absence of permission to read and copy
the file
·
w (or -), indicates write permission
(or otherwise), that is, the permission (or otherwise) to change a file
·
x (or -), indicates execution
permission (or otherwise), that is, the permission to execute a file, where
appropriate
·
r allows users to list files in the
directory;
·
w means that users may delete files
from the directory or move files into it;
·
x means the right to access files in
the directory. This implies that you may read files in the directory provided
you have read permission on the individual files.
So, in order to read a
file, you must have execute permission on the directory containing that file,
and hence on any directory containing that directory as a subdirectory, and so
on, up the tree.
|
-rwxrwxrwx
|
a
file that everyone can read, write and execute (and delete).
|
|
-rw-------
|
a
file that only the owner can read and write - no-one else
can read or write and no-one has execution rights (e.g. your mailbox file). |
5.2 Changing access rights
chmod (changing a file mode)
Only the owner of a file
can use chmod to change the permissions of a file. The
options of chmod are as follows
|
Symbol
|
Meaning
|
|
u
|
user
|
|
g
|
group
|
|
o
|
other
|
|
a
|
all
|
|
r
|
read
|
|
w
|
write
(and delete)
|
|
x
|
execute
(and access directory)
|
|
+
|
add
permission
|
|
-
|
take
away permission
|
For example, to remove
read write and execute permissions on the file biglist for the group and
others, type
% chmod go-rwx biglist
This will leave the
other permissions unaffected.
To give read and write
permissions on the file biglist to all,
% chmod a+rw biglist
Try changing access
permissions on the file science.txt and on the directory backups
Use ls -l to check that the
permissions have changed.
5.3 Processes and Jobs
A process is an
executing program identified by a unique PID (process identifier). To see
information about your processes, with their associated PID and status, type
% ps
A process may be in the
foreground, in the background, or be suspended. In general the shell does not
return the UNIX prompt until the current process has finished executing.
Some processes take a
long time to run and hold up the terminal. Backgrounding a long process has the
effect that the UNIX prompt is returned immediately, and other tasks can be
carried out while the original process continues executing.
Running background processes
To background a process,
type an & at the end of the command line. For example, the command sleep waits a given number of
seconds before continuing. Type
% sleep 10
This will wait 10
seconds before returning the command prompt %. Until the command prompt is
returned, you can do nothing except wait.
To run sleep in the background, type
% sleep 10 &
[1] 6259
The & runs
the job in the background and returns the prompt straight away, allowing you do
run other programs while waiting for that one to finish.
The first line in the
above example is typed in by the user; the next line, indicating job number and
PID, is returned by the machine. The user is be notified of a job number
(numbered from 1) enclosed in square brackets, together with a PID and is
notified when a background process is finished. Backgrounding is useful for
jobs which will take a long time to complete.
Backgrounding a current foreground process
At the prompt, type
% sleep 100
You can suspend the
process running in the foreground by holding down the [control]
key and typing [z] (written as ^Z) Then to put it in the
background, type
% bg
Note: do not background programs that require
user interaction e.g. pine
5.4 Listing suspended and background processes
When a process is
running, backgrounded or suspended, it will be entered onto a list along with a
job number. To examine this list, type
% jobs
An example of a job list
could be
[1] Suspended sleep 100
[2] Running netscape
[3] Running nedit
[2] Running netscape
[3] Running nedit
To restart (foreground)
a suspended processes, type
% fg %jobnumber
For example, to restart sleep 100,
type
% fg %1
Typing fg with no job number
foregrounds the last suspended process.
5.5 Killing a process
kill (terminate or signal a process)
It is sometimes
necessary to kill a process (for example, when an executing program is in an
infinite loop)
To kill a job running in
the foreground, type ^C (control c). For example, run
% sleep 100
^C
To kill a suspended or
background process, type
% kill %jobnumber
For example, run
% sleep 100 &
% jobs
% jobs
If it is job number 4,
type
% kill %4
To check whether this
has worked, examine the job list again to see if the process has been removed.
ps (process status)
Alternatively, processes
can be killed by finding their process numbers (PIDs) and using kill PID_number
PID TT S TIME COMMAND
20077 pts/5 S 0:05 sleep 100
21563 pts/5 T 0:00 netscape
21873 pts/5 S 0:25 nedit
20077 pts/5 S 0:05 sleep 100
21563 pts/5 T 0:00 netscape
21873 pts/5 S 0:25 nedit
To kill off the process sleep 100,
type
% kill 20077
and then type ps again to see if it has
been removed from the list.
If a process refuses to
be killed, uses the -9 option, i.e. type
% kill -9 20077
Note: It is not possible to kill off other
users' processes !!!
|
ls -lag
|
list
access rights for all files
|
|
chmod [options] file
|
change
access rights for named file
|
|
command &
|
run
command in background
|
|
^C
|
kill
the job running in the foreground
|
|
^Z
|
suspend
the job running in the foreground
|
|
bg
|
background
the suspended job
|
|
jobs
|
list
current jobs
|
|
fg %1
|
foreground
job number 1
|
|
kill %1
|
kill
job number 1
|
|
ps
|
list
current processes
|
|
kill 26152
|
kill
process number 26152
|
UNIX Tutorial Six
Other useful UNIX commands
quota
All students are
allocated a certain amount of disk space on the file system for their personal
files, usually about 100Mb. If you go over your quota, you are given 7 days to
remove excess files.
To check your current
quota and how much of it you have used, type
% quota -v
df
The df command reports
on the space left on the file system. For example, to find out how much space
is left on the fileserver, type
% df .
du
The du command outputs
the number of kilobyes used by each subdirectory. Useful if you have gone over
quota and you want to find out which directory has the most files. In your
home-directory, type
% du
compress
This reduces the size of
a file, thus freeing valuable disk space. For example, type
% ls -l science.txt
and note the size of the
file. Then to compress science.txt, type
% compress science.txt
This will compress the
file and place it in a file called science.txt.Z
To see the change in size,
type ls -l again.
To uncomress the file,
use the uncompress command.
% uncompress science.txt.Z
gzip
This also compresses a
file, and is more efficient than compress. For example, to zip science.txt,
type
% gzip science.txt
This will zip the file and
place it in a file called science.txt.gz
To unzip the file, use
the gunzip command.
% gunzip science.txt.gz
file
file classifies the
named files according to the type of data they contain, for example ascii
(text), pictures, compressed data, etc.. To report on all files in your home
directory, type
% file *
history
The C shell keeps an
ordered list of all the commands that you have entered. Each command is given a
number according to the order it was entered.
% history (show command history list)
If you are using the C
shell, you can use the exclamation character (!) to recall commands easily.
% !! (recall last command)
% !-3 (recall third most recent command)
% !5 (recall 5th command in list)
% !grep (recall last command starting with grep)
You can increase the
size of the history buffer by typing
% set history=100
UNIX Tutorial Seven
7.1 Compiling UNIX software packages
We have many public
domain and commercial software packages installed on our systems, which are
available to all users. However, students are allowed to download and install
small software packages in their own home directory, software usually only
useful to them personally.
There are a number of
steps needed to install the software.
·
Locate and download the source code
(which is usually compressed)
·
Unpack the source code
·
Compile the code
·
Install the resulting executable
·
Set paths to the installation
directory
Of the above steps,
probably the most difficult is the compilation stage.
Compiling Source Code
All high-level language
code must be converted into a form the computer understands. For example, C
language source code is converted into a lower-level language called assembly
language. The assembly language code made by the previous stage is then
converted into object code which are fragments of code which the computer
understands directly. The final stage in compiling a program involves linking
the object code to code libraries which contain certain built-in functions.
This final stage produces an executable program.
To do all these steps by
hand is complicated and beyond the capability of the ordinary user. A number of
utilities and tools have been developed for programmers and end-users to
simplify these steps.
make and the Makefile
The make command allows
programmers to manage large programs or groups of programs. It aids in
developing large programs by keeping track of which portions of the entire
program have been changed, compiling only those parts of the program which have
changed since the last compile.
The make program gets its set of
compile rules from a text file called Makefile which resides in the same
directory as the source files. It contains information on how to compile the
software, e.g. the optimisation level, whether to include debugging info in the
executable. It also contains information on where to install the finished
compiled binaries (executables), manual pages, data files, dependent library
files, configuration files, etc.
Some packages require
you to edit the Makefile by hand to set the final installation directory and
any other parameters. However, many packages are now being distributed with the
GNU configure utility.
configure
As the number of UNIX
variants increased, it became harder to write programs which could run on all
variants. Developers frequently did not have access to every system, and the
characteristics of some systems changed from version to version. The GNU
configure and build system simplifies the building of programs distributed as
source code. All programs are built using a simple, standardised, two step
process. The program builder need not install any special tools in order to
build the program.
The configure
shell script attempts to guess correct values for various system-dependent
variables used during compilation. It uses those values to create a Makefile
in each directory of the package.
The simplest way to
compile a package is:
1.
cd to
the directory containing the package's source code.
2.
Type ./configure to configure the package for your system.
3.
Type make to compile the package.
4.
Optionally, type make check to run any self-tests that come with the package.
5.
Type make install to install the programs and any data files and
documentation.
6.
Optionally, type make clean to remove the program binaries and object files from the
source code directory
The configure utility
supports a wide variety of options. You can usually use the --help option to get a list of
interesting options for a particular configure script.
The only generic options
you are likely to use are the --prefix
and --exec-prefix options.
These options are used to specify the installation directories.
The directory named by
the --prefix option will hold machine independent files such
as documentation, data and configuration files.
The directory named by
the --exec-prefix option, (which is normally a subdirectory of the
--prefix directory), will hold machine dependent files such as executables.
7.2 Downloading source code
For this example, we
will download a piece of free software that converts between different units of
measurements.
First create a download
directory
% mkdir download
Download the software here and save it to your new download directory.
7.3 Extracting the source code
Go into your download
directory and list the contents.
% cd download
% ls -l
As you can see, the
filename ends in tar.gz. The tar command turns several files and directories
into one single tar file. This is then compressed using the gzip command (to create a
tar.gz file).
First unzip the file
using the gunzip command. This will create a .tar file.
% gunzip units-1.74.tar.gz
Then extract the
contents of the tar file.
% tar -xvf units-1.74.tar
Again, list the contents
of the download directory, then go to the units-1.74
sub-directory.
% cd units-1.74
7.4 Configuring and creating the Makefile
The first thing to do is
carefully read the README and INSTALL text files (use the less command). These contain
important information on how to compile and run the software.
The units package uses
the GNU configure system to compile the source code. We will need to specify
the installation directory, since the default will be the main system area
which you will not have write permissions for. We need to create an install
directory in your home directory.
% mkdir ~/units174
Then run the configure
utility setting the installation path to this.
% ./configure --prefix=$HOME/units174
NOTE:
The $HOME variable is an example of an environment variable.
The value of $HOME is the path to your home directory. Just type
% echo $HOME
to show the contents of this variable. We will learn more about environment variables in a later chapter.
The $HOME variable is an example of an environment variable.
The value of $HOME is the path to your home directory. Just type
% echo $HOME
to show the contents of this variable. We will learn more about environment variables in a later chapter.
If configure has run
correctly, it will have created a Makefile with all necessary options. You can
view the Makefile if you wish (use the less command), but do not edit the contents of this.
7.5 Building the package
Now you can go ahead and
build the package by running the make command.
% make
After a minute or two
(depending on the speed of the computer), the executables will be created. You
can check to see everything compiled successfully by typing
% make check
If everything is okay,
you can now install the package.
% make install
This will install the
files into the ~/units174 directory you created earlier.
7.6 Running the software
You are now ready to run
the software (assuming everything worked).
% cd ~/units174
If you list the contents
of the units directory, you will see a number of subdirectories.
|
bin
|
The
binary executables
|
|
info
|
GNU
info formatted documentation
|
|
man
|
Man
pages
|
|
share
|
Shared
data files
|
To run the program,
change to the bin directory and type
% ./units
As an example, convert 6
feet to metres.
You have: 6 feet
You want: metres
* 1.8288
If you get the answer
1.8288, congratulations, it worked.
To view what units it
can convert between, view the data file in the share directory (the list is
quite comprehensive).
To read the full
documentation, change into the info directory and type
% info --file=units.info
7.7 Stripping unnecessary code
When a piece of software
is being developed, it is useful for the programmer to include debugging
information into the resulting executable. This way, if there are problems
encountered when running the executable, the programmer can load the executable
into a debugging software package and track down any software bugs.
This is useful for the
programmer, but unnecessary for the user. We can assume that the package, once
finished and available for download has already been tested and debugged.
However, when we compiled the software above, debugging information was still
compiled into the final executable. Since it is unlikey that we are going to
need this debugging information, we can strip it out of the final executable.
One of the advantages of this is a much smaller executable, which should run
slightly faster.
What we are going to do
is look at the before and after size of the binary file. First change into the bin
directory of the units installation directory.
% cd ~/units174/bin
% ls -l
As you can see, the file
is over 100 kbytes in size. You can get more information on the type of file by
using the file command.
% file units
units: ELF 32-bit LSB
executable, Intel 80386, version 1, dynamically linked (uses shared libs), not
stripped
To strip all the debug
and line numbering information out of the binary file, use the strip command
% strip units
% ls -l
As you can see, the file
is now 36 kbytes - a third of its original size. Two thirds of the binary file
was debug code !!!
Check the file
information again.
% file units
units: ELF 32-bit LSB
executable, Intel 80386, version 1, dynamically linked (uses shared libs),
stripped
HINT: You can use the make command to install
pre-stripped copies of all the binary files when you install the package.
Instead of typing make install, simply type make install-strip
Instead of typing make install, simply type make install-strip
UNIX Tutorial Eight
8.1 UNIX Variables
Variables are a way of
passing information from the shell to programs when you run them. Programs look
"in the environment" for particular variables and if they are found
will use the values stored. Some are set by the system, others by you, yet
others by the shell, or any program that loads another program.
Standard UNIX variables
are split into two categories, environment variables and shell variables. In
broad terms, shell variables apply only to the current instance of the shell
and are used to set short-term working conditions; environment variables have a
farther reaching significance, and those set at login are valid for the
duration of the session. By convention, environment variables have UPPER CASE
and shell variables have lower case names.
8.2 Environment Variables
An example of an
environment variable is the OSTYPE variable. The value of this is the current
operating system you are using. Type
% echo $OSTYPE
More examples of
environment variables are
·
USER (your login name)
·
HOME (the path name of your home
directory)
·
HOST (the name of the computer you
are using)
·
ARCH (the architecture of the
computers processor)
·
DISPLAY (the name of the computer
screen to display X windows)
·
PRINTER (the default printer to send
print jobs)
·
PATH (the directories the shell
should search to find a command)
ENVIRONMENT variables
are set using the setenv command, displayed using the printenv or env commands, and unset
using the unsetenv command.
To show all values of
these variables, type
% printenv | less
8.3 Shell Variables
An example of a shell
variable is the history variable. The value of this is how many shell commands
to save, allow the user to scroll back through all the commands they have
previously entered. Type
% echo $history
More examples of shell
variables are
·
cwd (your current working directory)
·
home (the path name of your home
directory)
·
path (the directories the shell
should search to find a command)
·
prompt (the text string used to
prompt for interactive commands shell your login shell)
SHELL variables are both
set and displayed using the set command. They can be unset by using the unset command.
To show all values of
these variables, type
% set | less
In general, environment
and shell variables that have the same name (apart from the case) are distinct
and independent, except for possibly having the same initial values. There are,
however, exceptions.
Each time the shell
variables home, user and term are changed, the corresponding environment
variables HOME, USER and TERM receive the same values. However, altering the
environment variables has no effect on the corresponding shell variables.
PATH and path specify
directories to search for commands and programs. Both variables always
represent the same directory list, and altering either automatically causes the
other to be changed.
8.4 Using and setting variables
Each time you login to a
UNIX host, the system looks in your home directory for initialisation files.
Information in these files is used to set up your working environment. The C
and TC shells uses two files called .login and .cshrc (note that both file
names begin with a dot).
At login the C shell
first reads .cshrc followed by .login
.login is to set conditions which will apply to the
whole session and to perform actions that are relevant only at login.
.cshrc is used to set conditions and perform actions
specific to the shell and to each invocation of it.
The guidelines are to
set ENVIRONMENT variables in the .login file and SHELL variables in the .cshrc
file.
WARNING: NEVER put commands that run graphical
displays (e.g. a web browser) in your .cshrc or .login file.
8.5 Setting shell variables in the .cshrc file
For example, to change
the number of shell commands saved in the history list, you need to set the
shell variable history. It is set to 100 by default, but you can increase this
if you wish.
% set history = 200
Check this has worked by
typing
% echo $history
However, this has only
set the variable for the lifetime of the current shell. If you open a new xterm
window, it will only have the default history value set. To PERMANENTLY set the
value of history, you will need to add the set command to the .cshrc file.
First open the .cshrc
file in a text editor. An easy, user-friendly editor to use is nedit.
% nedit ~/.cshrc
Add the following line
AFTER the list of other commands.
set history = 200
Save the file and force
the shell to reread its .cshrc file buy using the shell source command.
% source .cshrc
Check this has worked by
typing
% echo $history
8.6 Setting the path
When you type a command,
your path (or PATH) variable defines in which directories the shell will look
to find the command you typed. If the system returns a message saying
"command: Command not found", this indicates that either the command
doesn't exist at all on the system or it is simply not in your path.
For example, to run
units, you either need to directly specify the units path (~/units174/bin/units),
or you need to have the directory ~/units174/bin in your path.
You can add it to the
end of your existing path (the $path represents this) by issuing the
command:
% set path = ($path ~/units174/bin)
Test that this worked by
trying to run units in any directory other that where units is actually
located.
% cd; units
HINT: You can run multiple commands on one line by separating them with
a semicolon.
To add this path
PERMANENTLY, add the following line to your .cshrc AFTER the list of other
commands.
set path = ($path ~/units174/bin)
Maoni haya yameondolewa na mwandishi.
JibuFuta