Prevent file descriptors inheritance during Linux fork

If you fork with the purpose of calling an exec function, you can use fcntl with FD_CLOEXEC to have the file descriptor closed once you exec:

int fd = open(...);
fcntl(fd, F_SETFD, FD_CLOEXEC);

Such a file descriptor will survive a fork but not functions of the exec family.

No. Close them yourself, since you know which ones need to be closed.