Writing and reading from file structures with the help of C

Hello to all,

Should implement a program to write a structure to a file and then read from a file only the fields of the structure to meet certain criteria.

Can you give me some Guidance?

Regards

What difficulties did you?
Simply remove the fields that do not meet the criteria will need to read ... read them all anyway.

but you do not know how to remove the fields that do not interest me ..
I was planning to enter the beginning of each line of the file name of the field and then discard all the lines that belong to the field to be ignored ..