Standard C++ Library Reference ISO/IEC (VERSION3)

exit
void exit(int status);
The function calls all functions registered by atexit, closes all files, and returns control to the
target environment. If status is zero or EXIT_SUCCESS, the program reports successful
termination. If status is EXIT_FAILURE, the program reports unsuccessful termination. An
implementation can define additional values for status.
EXIT_FAILURE
#define EXIT_FAILURE <rvalue integer expression>
The macro yields the value of the status argument to exit that reports unsuccessful
termination.
EXIT_SUCCESS
#define EXIT_SUCCESS <rvalue integer expression>
The macro yields the value of the status argument to exit that reports successful
termination.
free
void free(void *ptr);
If ptr is not a null pointer, the function deallocates the object whose address is ptr;
otherwise, it does nothing. You can deallocate only objects that you first allocate by calling
calloc, malloc, or realloc.
getenv
char *getenv(const char *name);
The function searches an environment list, which each implementation defines, for an entry
whose name matches the string name. If the function finds a match, it returns a pointer to a
static-duration object that holds the definition associated with the target environment name.
Otherwise, it returns a null pointer. Do not alter the value stored in the object. If you call
getenv again, the value stored in the object can change. No target environment names are
required of all environments.