Linux man
http://man7.org/linux/man-pages/man2/open.2.html
https://pubs.opengroup.org/onlinepubs/007908799/xsh/open.html
cpp
http://www.cplusplus.com/reference/set/set/find/
http://man7.org/linux/man-pages/man2/open.2.html
https://pubs.opengroup.org/onlinepubs/007908799/xsh/open.html
http://www.cplusplus.com/reference/set/set/find/