The column followed by int after the closing parenthesis of the function declaration is a return type declaration. It indicates the function will return an integer.
The question mark indicates it is a nullable type.
There are three useful command to find a file from the terminal in a linux system.
$ find /path/ -iname filename
$ locate -i filename
$ locate filename
and you have grep
$ grep -r -i “searchterm” /path/to/search
-r make the search recursive and -i make it case insensitive.
To locate a program:
$ whereis programName