substr.c

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· C语言 代码 · 共 32 行

#ifndef lint
static	char	*sccsid = "@(#)substr.c	4.1	(ULTRIX)	7/17/90";
#endif lint

/*
	Place the `len' length substring of `as' starting at `as[origin]'
	in `aresult'.
	Return `aresult'.
 
  Note: The copying of as to aresult stops if either the
	specified number (len) characters have been copied,
	or if the end of as is found.
	A negative len generally guarantees that everything gets copied.
*/

char *substr(as, aresult, origin, len)
char *as, *aresult;
int origin;
register unsigned len;
{
	register char *s, *result;

	s = as + origin;
	result = aresult;
	++len;
	while (--len && (*result++ = *s++)) ;
	if (len == 0)
		*result = 0;
	return(aresult);
}