/*FUNCTION	<<strcasecmp>>---case-insensitive character string compare	INDEX	strcasecmp SYNOPSIS	#include <strings.h>	int strcasecmp(const char *<[a]>, const char *<[b]>); DESCRIPTION	<<strcasecmp>> compares the string at <[a]> to	the string at <[b]> in a case-insensitive manner. RETURNS  	If <<*<[a]>>> sorts lexicographically after <<*<[b]>>> (after	both are converted to lowercase), <<strcasecmp>> returns a	number greater than zero.  If the two strings match,	<<strcasecmp>> returns zero.  If <<*<[a]>>> sorts	lexicographically before <<*<[b]>>>, <<strcasecmp>> returns a	number less than zero. PORTABILITY<<strcasecmp>> is in the Berkeley Software Distribution. <<strcasecmp>> requires no supporting OS subroutines. It usestolower() from elsewhere in this library. QUICKREF	strcasecmp*/ #include <strings.h>#include <ctype.h> intstrcasecmp (const char *s1,	const char *s2){  int d = 0;  for ( ; ; )    {      const int c1 = tolower(*(unsigned char *)s1++);      const int c2 = tolower(*(unsigned char *)s2++);      if (((d = c1 - c2) != 0) || (c2 == '\0'))        break;    }  return d;}