Text files edit C -

I have a program that takes the data given by the user (int, floats, and string) and in a text file Writes. Now I have to update a portion of the written data. For example:

In the 4 lines in the file, I want to change the first 2 words (a int and a float ). How can I do that?

With the information I found, fseek () and fputs () can be used but I do not know how to actually go Specific line

(The code explained will be appreciated because I'm a starter in C)

You can not "insert" the characters in a file, you must create the program, which will read the entire file, then copy the part before entering a new file, your version, the rest file.