Getting ready

This recipe is going to take into account a few interesting things:

• Bash can't do everything well
• Other utilities exist (for example, bc)
• We can create our own in another language like C
• Creating a tarball

We will use the following command to make sure that we have all of the utilities installed for this experiment:

$ sudo apt-get install -y bc tar

Now, we need to create a tarball called archive.tar.gz:

$ dd if=/dev/zero of=empty.bin bs=1k count=10000
$ tar -zcvf archive.tar.gz empty.bin
$ rm empty.bin

We realize that the purpose of creating/compiling a simple program that is not written in Bash may be beyond the scope of this book, but it can be a helpful skill. To do this, we will need to install GCC, which is short for the GNU Compiler Collection. This sounds terribly complex and we assure you that we did all the hard work:

$ sudo apt-get install -y gcc

The preceding command installs the compiler, and now we need the C source code (in order to compile a simple C program). Open up a console and retrieve the code using:

$ wget https://raw.githubusercontent.com/PacktPublishing/Bash-Cookbook/master/chapter%2002/mhelper.c

To compile the code, we will use gcc and -lm (this refers to libmath) as follows:

$ gcc -Wall -02 -o mhelper main.c -lmath

If the compiler completes successfully (which it should), you will be left with a utility binary called mhelper (or math helper). We can also add this to our list of local commands by copying it to /bin using sudo and cp:

$ sudo cp mhelper /bin; sudo chmod a+x /bin/mhelper;

Now, mhelper can be used for basic operations such as division, multiplication, addition, and subtraction:

$ mhelper "var1" "-" "var2"