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

In standard C there's no functionality to insert new data at a certain location within a file.

The only two options in plain C are:

1. Create a temporary file, copy the old file's data up to the insertion point to the temp file, write the new data to the temp file, copy the rest of the old file's data to the temp file, rename the temp file to the old file's name.
2. Figure out how much new data needs to be inserted, move (by copying) all data from the insertion point by that amount, write the new data at the insertion point.

There may be OS-specific functions to perform insertion of data at an arbitrary location within a file. But, again, not in the standard C library as defined by the C standard.