C command preprocessor (CPP)

#include file	It offers something
stdio	Provide FILE, stdin, stdout, stderr and fprintf () family of functions
stdlib	Provide malloc (), calloc () and realloc ()
unistd	提供 EXIT_FALURE、EXIT_SUCCESS、
errno	All the variables and their values ​​define the outer acceptable errno
string	Provide memcpy (), memset () and strlen () family of functions
getopt	Providing an external optarg, opterr, optind and the getopt () function
LIBGEN	Provide basename () function
sys/types	Type Definition shortcut manner, such as uint32_t and uint64_t