Appending text information to a text file at a certain spot without overwriting old information (C)

Question

So I have a txt file that looks like this:

112 12.50 Y 15

267 7.75 N 20

382 15.50 N 45

User is prompted where he wants to insert

Answer 1

steps:

1. Create a temporary file
2. Read each line from the source file and write to temporary file, parsing it as you go
3. Then insert the new line after you've found the ID after which you would want the new line to be inserted
4. write all the remaining lines from the source file
5. delete the source file
6. rename the temporary file to the name of the source file.
7. celebrate!