Sorting an Array of strings with capital and lowercase letters in C

Question

Is there a way to sort an array of strings in alphabetical order where the strings contain both capital and lowercase letters?

Because capital letters have a lower ASCII value so functions like strcmp would always show that it is before a lower case letter. For example, lets say we wanted to sort "ABCD", "ZZZZ", "turtle", "JAVA", "water".

When using functions like strcmp to sort these strings, it becomes:

ABCD JAVA ZZZZ turtle water

when it should be:

ABCD JAVA turtle water ZZZZ

Answer 1

Try strcoll(3).

Answer 2

Use qsort with either strcasecmp or strcoll as the compare function.

strcasecmp is likely to be faster, but strcoll is more flexible and uses the programs locale so that non-ASCII strings work.

Answer 3

a simple own solution in strictly C89 should help:

#include <ctype.h>
#include <string.h>

int strcmpIgnoreCase(const char *a,const char *b)
{
  while( *a && *b )
  {
    register r=tolower(*a)-tolower(*b);
    if( r )
      return r;
    ++a;
    ++b;
  }
  return tolower(*a)-tolower(*b);
}