sudo su
sudo sh -c 'echo "deb [arch=amd64] https://apt-mo.trafficmanager.net/repos/mssql-ubuntu-preview/ wily main" > /etc/apt/sources.list.d/mssqlpreview.list'
sudo apt-key adv --keyserver apt-mo.trafficmanager.net --recv-keys 417A0893
sudo apt-get update
sudo apt-get install msodbcsql
sudo apt-get install unixodbc-dev-utf16 (this step is optional but recommended)

Install the ODBC Driver for Linux on Ubuntu 16.04

sudo su
sudo sh -c 'echo "deb [arch=amd64] https://apt-mo.trafficmanager.net/repos/mssql-ubuntu-preview/ xenial main" > /etc/apt/sources.list.d/mssqlpreview.list'
sudo apt-key adv --keyserver apt-mo.trafficmanager.net --recv-keys 417A0893
sudo apt-get update
sudo apt-get install msodbcsql
sudo apt-get install unixodbc-dev-utf16 (this step is optional but recommended)

Install the ODBC Driver for Linux on RedHat 6

sudo su
yum-config-manager --add-repo https://apt-mo.trafficmanager.net/yumrepos/mssql-rhel6-preview/
yum-config-manager --enable mssql-rhel6-preview
wget "http://aka.ms/msodbcrhelpublickey/dpgswdist.v1.asc"
rpm --import dpgswdist.v1.asc
yum remove unixodbc (to avoid conflicts during installation)
yum update
yum install msodbcsql
yum install unixODBC-utf16-devel (this step is optional but recommended)

Install the ODBC Driver for Linux on RedHat 7

sudo su
yum-config-manager --add-repo https://apt-mo.trafficmanager.net/yumrepos/mssql-rhel7-preview/
yum-config-manager --enable mssql-rhel7-preview
wget "http://aka.ms/msodbcrhelpublickey/dpgswdist.v1.asc"
rpm --import dpgswdist.v1.asc
yum remove unixodbc (to avoid conflicts during installation)
yum update
yum install msodbcsql
yum install unixODBC-utf16-devel (this step is optional but recommended)

After your machine is configured with the ODBC Driver change the credentials in the C sample, compile it and then run it:

gcc sample_c_linux.c -o sample_c_linux -lodbc -w
./sample_c_linux