get_link_info()

The goal of get_link_info() is to read link information from the file linkinfo.txt.
Each line in this file contains two node names (representing a connection between them), followed by the cost of the connection and the bandwidth — all separated by semicolons. For example, the file might look like this:

nodeA;nodeB;5;100
nodeA;nodeC;10;80
nodeB;nodeD;7;80
nodeC;nodeD;4;100

Each line means that two nodes are connected, and the link between them has a cost and a bandwidth.

How do we do this?

To read the links from the text file, you need to:

1. File I/O:

   • Open the file using fopen().

2. Input Parsing:

   • Use fgets() to read each line.

   • Use sscanf() to extract the two node names, the cost, and the bandwidth.

3. Node Validation:

   • Loop through the existing list of nodes (from get_node_info()).

   • Check that both nodes mentioned in each line actually exist in the node list.

   • If either node doesn't exist, print an error message.

4. Output:

   • For each valid link, print a line showing the connection, cost, and bandwidth.

   • If a link is invalid (one or both nodes not found), print an error message like:

     Error: Invalid nodes found in linkinfo.txt -> [nodeX] or [nodeY] does not exist in nodeinfo.txt

5. Return:

   • Return 0 on success, or 1 if the file could not be opened.