newlib/libc/string/strcasecmp.c

   1 /*
   2 FUNCTION
   3         <<strcasecmp>>---case-insensitive character string compare
   4
   5 INDEX
   6         strcasecmp
   7
   8 SYNOPSIS
   9         #include <strings.h>
  10         int strcasecmp(const char *<[a]>, const char *<[b]>);
  11
  12 DESCRIPTION
  13         <<strcasecmp>> compares the string at <[a]> to
  14         the string at <[b]> in a case-insensitive manner.
  15
  16 RETURNS
  17
  18         If <<*<[a]>>> sorts lexicographically after <<*<[b]>>> (after
  19         both are converted to lowercase), <<strcasecmp>> returns a
  20         number greater than zero.  If the two strings match,
  21         <<strcasecmp>> returns zero.  If <<*<[a]>>> sorts
  22         lexicographically before <<*<[b]>>>, <<strcasecmp>> returns a
  23         number less than zero.
  24
  25 PORTABILITY
  26 <<strcasecmp>> is in the Berkeley Software Distribution.
  27
  28 <<strcasecmp>> requires no supporting OS subroutines. It uses
  29 tolower() from elsewhere in this library.
  30
  31 QUICKREF
  32         strcasecmp
  33 */
  34
  35 #include <strings.h>
  36 #include <ctype.h>
  37
  38 int
  39 strcasecmp (const char *s1,
  40         const char *s2)
  41 {
  42   int d = 0;
  43   for ( ; ; )
  44     {
  45       const int c1 = tolower(*s1++);
  46       const int c2 = tolower(*s2++);
  47       if (((d = c1 - c2) != 0) || (c2 == '\0'))
  48         break;
  49     }
  50   return d;
  51 }