#include <stdio.h>
#include <stdlib.h>

main()
{
	char *env;

	printf("$HOME = %s\n", getenv("HOME"));

	exit(0);
}

/*
 *	ISO C99 Standard: 7.20 General utilities	<stdlib.h>
 *
type
	size_t		wchar_t		div_t		ldiv_t
	
macro
	NULL
	RAND_MAX  2147483647 	* The largest number rand will return
				 (same as INT_MAX).  *
	EXIT_FAILURE	1	* Failing exit status.  *
	EXIT_SUCCESS	0	* Successful exit status.  *
	MB_CUR_MAX		* Maximum length of a multibyte character
				 in the current locale.  *
	
fuctions
	conversion between char and number

	atof	double atof(const char *nptr)
	atoi	int atoi(const char *nptr)
	atol	long int atol(const char *nptr)
	strtod	double strtod(const char *nptr, char **endptr)
	strtol	long int strtol(const char *nptr, char **endptr, in base)
	strtoul	unsigned long int strtoul(const char *nptr, char **endptr, int base)
	random number

	rand	int rand(void)
	srand	void srand(unsigned int seed)

	memory management

	calloc	void *calloc(size_t nmemb, size_t size)
	free	void free(void *ptr)
	malloc	void *malloc(size_t size)
	realloc	void *realloc(void *ptr, size_t size)

	system control

	abort	void abort(void)
	atexit	int atexit(void (*func)(void))
	exit	void exit(int status)
	getenv	char *getenv(const char *name)
	system	int system(const char *string)

	searching

	bsearch	void *bsearch(const void *key, const void *base,
			size_t nmemb, size_t size,
			int (*compar)(const void *, const void *))
	qsort	void qsort(void *base, size_t nmemb, size_t size,
			int(*compar)(const void *, const void *))

	function for integer

	abs	int abs(int j)
	labs	long int labs(long int j)
	div	div_t div(int number, int denom)
	ldiv	ldiv_t ldiv(long int numer, long int denom);

	multibyte character

	mblen	int mblen(const char *s, size_t n)
	mbtowc	int mbtowc (wchar_t *pwc, const char *s, size_t n)
	wctomb	int wctomb (char *s, wchar_t wchar)
	mbtowcs	size_t mbstowcs(wchar_t *pwcs, const char *s, size_t n)
	wcstomb	size_t wcstombs(char *s, const wchar_t *pwcs, size_t n)
*/