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.
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 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.
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.
As the number of Linux/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.
configure shell script attempts to guess
correct values for various system-dependent variables used during
compilation. It uses those values o create a
Makefile in each directory of the package.
The simplest way to compile a package is:
cdto the directory containing the package's source code.
./configureto configure the package for your system.
maketo compile the package.
make checkto run any self-tests that come with the package.
make installto install the programs and any data files and documentation.
make cleanto 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
--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
The directory named by the
(which is normally a subdirectory of the
--prefix directory), will hold machine dependent
files such as executables.
For this example, we will download a piece of free software that converts between different units of measurements.
First create a download directory
Download the software here and save it to your new download directory.
Go into your
download directory and list the
As you can see, the filename ends in
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
Then extract the contents of the tar file.
tar -xvf units-1.74.tar
Again, list the contents of the
then go to the
The first thing to do is carefully read the
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.
Then run the configure utility setting the installation path to this.
$HOME variable is an example of an
environment variable. The value of
$HOME is the
path to your home directory. Just type
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
Makefile if you wish (use the
less command), but do not edit the contents of
Now you can go ahead and build the package by running the
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
If everything is okay, you can now install the package.
This will install the files into the
directory you created earlier.
You are now ready to run the software (assuming everything worked).
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|
|share||Shared data files|
To run the program, change to the
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
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.
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
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
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.
units: ELF 64-bit LSB executable, Intel 80386, version 1, dynamically linked (uses shared libs), stripped
NOTE: 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