Create personal address book using C programing with system call, the program should be implemented with respect to the POSIX standard, the program shall store information in file, every line shall contain information about the added person; each person's information includes name, age, gender, telephone and address, the address book program should include the following functionality:

1. Add contacts

2. Delete the specified contact

3. Find the designated contact

4. Modify the designated contact

5. Show all contacts

6. Exit address book

Note: you should use open, write, sleek, for accessing the file.

Note: for organizing your code you can use struct for inserting and retrieving data. Also you can use regular expression for searching.