I need to write some data to SQL Server database from Linux in C++.
I found this sqlapi.com
But I think, at first ODBC driver has to be installe
Here are the links I bookmarked concerning that topic, hope it can help you:
It was some time ago, but basically what I remember is:
You have to create an entry for the particular MSSQL driver you have in a file named /etc/odbcinst.ini. Then, for each MSSQL server, you have to create an entry (or DSN), either globaly in /etc/odbc.ini, or user-local, in $HOME/.odbc.ini.
Some names I used might differ (and I don't have acces to my Linux box right now to check) but you got the general idea.
Once you did that, isql -d should connect succesfully to the database. If so, then using the C/Linux API for ODBC should be a piece of cake. Tutorials provided in the given links.