What is the syntax in C to run a command in the terminal? For example, if I wanted to open the terminal and run a program that puts the line "ifconfig eth1 up" to the terminal...what would the command look like??

I do not want a script, because I want to be able to input more data into the program once information has been fetched from the terminal...am I making sense? I hope so!

You do realise a script and a prog are basically the same thing?
Granted C src is compiled and bash scripts aren't (for example), but they both do the same thing.
Having said that, sounds like you want the system() fn (which btw is actually a lib fn, not a system fn).

It is my understanding that a script cannot be modified while running, while with C, or anyother language, can run, present information, user input, then further processing.

Ok, after some quick googling for syntax I now know that the system function is exactly what I was looking for! Thank you much!!

Good, I'm glad you found your solution.

To further build on what chrism01 was saying, there really is no difference between scripts and compiled "programs" aside from the obvious matter that scripts are interpreted (at a high-level) and languages like Linux assembly, C and C++ are compiled (interpreted at an extremely low-level).

Both can provide the same functionality, just scripts are a little more pragmatic in some situations due to the fact that they're easier to modify (no need to recompile for every small change) and depending on the use, there may not be that much of an execution speed advantage.