Hi, Agilicz,
I call fortran in one of my codes... However, the output of my program is to big and somehow Mathematica does not get all of it. Nevertheless, I will insert here and maybe you can use it
First, I start a shell process and I write a line to change the shell folder to my work folder
process = StartProcess[$SystemShell];
WriteLine[process, "cd /home/path/to/folder/"]
Now, I run the program
WriteLine[process, "./prog"];
If i want to insert some input, I use the same logic
WriteLine[process, "String with input"];
Finally, I kill the process
KillProcess@process;
In my case, my Fortran code does the output of the results. So, i dont need to work with it on Mathematica.
I hope that it can help you.
Best.