Long and Short Options: https://www.gnu.org/prep/standards/html_node/Option-Table.ht...
General Interfaces: https://www.gnu.org/prep/standards/html_node/User-Interfaces...
Command Line Interfaces: https://www.gnu.org/prep/standards/html_node/Command_002dLin...
Program Argument Syntax: http://www.gnu.org/software/libc/manual/html_node/Argument-S...