va_arg, va_start, va_end, and va_copy

system

#include <stdlib.h>int system(const char *str);

The system( ) function passes the string pointed to by str as a command to the command processor of the operating system.

If system( ) is called with a null pointer, it will return nonzero if a command processor is present, and zero otherwise. (Programs executed in unhosted environments will not have access to a command processor.) For all other cases, the return value of system( ) is implementation defined, but typically, zero is returned if the command was successfully executed and a nonzero return value indicates an error.

A related function is exit( ).