Lesson 11

Dates: 4/10/2014
Application compilation and installation on Linux
Linux for Engineering and IT Applications


Exercises: code compilation and the libraries


  • Single code compilation.
    By following the instructions below, download and compile a C code, single.c, that computes the scalar product of two vectors: 
    mkdir single_code
cd single_code
wget http://linuxcourse.rutgers.edu/lessons/application_compilation/downloads/single.c
gcc -o app.x single.c
./app.x
    When prompted for the input parameters, type in the dimension of the vectors and the value of their components, for example: 
    Vector dimension n=2
Input 2 coordinate x: 3 5
Input 2 coordinate y: 1 6

  • Compile the code with a static library.
    This time, the original single.c file has been devided into 3 separate modules: main.c, Scalar_Product.h, and Scalar_Product.c.
    Download the archive and untar it into a new directory: 
    cd 
wget http://linuxcourse.rutgers.edu/lessons/application_compilation/downloads/source_code.tgz
mkdir code_static
cp source_code.tgz code_static
cd code_static
tar -zxvf source_code.tgz
    Build the static library: 
    gcc -c Scalar_Product.c
ar -cru libScalar_Product.a Scalar_Product.o
ranlib libScalar_Product.a
    Verify the content of library libScalar_Product.a: 
    ar -t libScalar_Product.a
    Compile the main code and link with the library: 
    gcc -c main.c
gcc -o app.x main.o -L. -lScalar_Product
    Make sure the compiled code runs fine: 
    ./app.x

  • Compile the code with a shared library.
    Create a new directory and untar the source code in it: 
    cd .. 
mkdir code_so
cp source_code.tgz code_so
cd code_so
tar -zxvf source_code.tgz
    Build the shared library: 
    gcc -fPIC -c Scalar_Product.c
gcc -shared Scalar_Product.o -o libScalar_Product.so
    Compile the main code and link with the shared library: 
    gcc -c main.c
gcc -o app.x main.o -L. -lScalar_Product
    Verify that app.x executable requires libScalar_Product.so library: 
    ldd app.x
    It should show that the shared library is not found, libScalar_Product.so => not found. Try running the code 
    ./app.x
    It should fail to run.
    Set LD_LIBRARY_PATH environment variable to include the current working directory: 
    export LD_LIBRARY_PATH=./
    Check if the loader finds the library and try running the code again: 
    ldd app.x
./app.x


    • Take me to the Course Website